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DESCRIPTION JP2012198526

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DESCRIPTION JP2012198526
Abstract: To provide an electronic keyboard instrument capable of reducing unnecessary
resonance generated in a space behind a speaker in a housing in an electronic musical
instrument incorporating a speaker. A musical tone generating circuit for supporting a keyboard
in a state where a playing part of the keyboard is exposed and generating a musical tone signal
according to the keyboard operation, and speakers 30a and 30b for emitting a musical tone
signal generated by the musical tone generating circuit. And the first sound emission path for
transmitting sound from the sound emission surfaces of the speakers 30a and 30b to the player
side, and the interior from behind the sound emission surfaces of the speakers 30a and 30b. A
second sound emission path is formed to propagate the sound to the side of the player via the
space. Resonators 32a and 32b that resonate at a specific resonance frequency generated in the
inner space by driving the speakers 30a and 30b are provided such that the control point is
located on the antinode of the sound pressure of the natural vibration mode of the resonance
frequency in the inner space. The resonance of the resonator reduces the sound pressure at the
antinode of the sound pressure. [Selected figure] Figure 3
Electronic keyboard instrument and sound adjustment system
[0001]
TECHNICAL FIELD The present invention relates to an electronic keyboard instrument, and to an
electronic keyboard instrument and an acoustic control system having an acoustic structure with
few acoustic characteristics generated from the instrument.
[0002]
According to Patent Document 1 below, in an electronic keyboard instrument having a housing in
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which a speaker is housed, it is necessary to emit the sound from the sound emitting surface of
the speaker so that the player can easily hear the sound emitted from the speaker. Instead, there
is disclosed an electronic keyboard instrument having a sound emission hole such as a tone
escape that emits a speaker's sound from the internal space of the case toward the player.
[0003]
JP, 2005-202190, A
[0004]
In the space behind the speaker of the case in which a speaker such as an electric keyboard
instrument is built, the vibration of the speaker causes a natural vibration form of resonance
frequency according to the shape of the case and the like.
The present invention provides, in an electronic musical instrument incorporating a speaker, an
electronic keyboard musical instrument capable of reducing unnecessary resonance occurring in
a space behind the speaker in a housing.
[0005]
In order to achieve the above object, an electronic keyboard instrument according to the present
invention emits a tone signal generated by the tone generation circuit, and a tone generation
circuit that generates a tone signal according to the operation of the keyboard, the keyboard An
electronic keyboard instrument having a speaker, and a case for accommodating the musical
tone generating circuit and the speaker in an internal space, and supporting the keyboard in a
state where the playing portion is exposed, the case emits sound from the speaker A first sound
emission path for guiding the sound emitted from the surface to the outside and propagating it
outside the housing, and the sound emitted from the back of the sound emission surface of the
speaker for propagating the sound outside the housing via the internal space A control point is
positioned at an antinode of sound pressure of a specific vibration style of a specific frequency
generated in the internal space by driving of the speaker, and resonates at the specific frequency.
Characterized by including a resonator for reducing the sound pressure at the location of the
antinode of Kion pressure.
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In this configuration, two or more of the speakers are provided, and a partition plate is provided
to divide the internal space so as to divide the two or more speakers into at least two or more,
and the resonator is divided by the partition plate The space is preferably provided in any two or
more of the space in which the speaker is located.
In this configuration, a second resonator is provided in the space in which the speaker is located,
and resonates at a frequency at which a vibration in the casing generates a reaction force to the
vibration operation when the speaker emits a sound, or A third resonance body for adjusting the
natural vibration mode such that an antinode of sound pressure of the natural vibration mode
different from the specific frequency is located at a position communicating with the outside of
the housing of the second sound emission path It is preferable to have at least one of the above.
[0006]
In the electronic keyboard instrument according to the present invention, a housing, a keyboard
including a plurality of keys disposed along the front side of the housing, and the keyboard on
the front side of the housing are provided. And a tone signal generation circuit disposed in the
internal space of the housing and generating a tone signal according to the operation of the
keyboard; and the tone signal generation circuit. At least one speaker for emitting a musical tone
signal, and at least one resonator disposed in the internal space of the housing, the housing being
provided with a sound emission surface of the at least one speaker The at least one resonator is
configured to form a sound output path for propagating the sound emitted to the outside of the
housing through the sound output hole via the internal space of the housing, A part of which has
an open part, and driving the speaker Accordingly, characterized in that it is intended to be
disposed in the antinode of the sound pressure of the natural vibration mode at a frequency
occurring in the internal space of the housing. In this configuration, the at least one resonator
comprises a tubular body of which one end is an open end as the open portion and the other end
is a closed end, and the diameter of the tubular body is the open end And the tubular body is
disposed such that its axis is parallel to the arranging direction in which the plurality of keys are
arranged in the inner space of the housing. Is preferred. Further, in this configuration, it is
preferable that the tubular body is disposed with the open end directed toward an end of the
internal space of the housing in the arrangement direction of the plurality of keys. In this
configuration, the at least one resonator is configured as at least four resonators, and two of the
at least four resonators have respective open ends in the arrangement direction of the plurality
of keys. At least two of the at least four resonators are disposed toward the respective ends of the
internal space of the housing, and at least two of the at least four resonators have respective
open ends in the arrangement direction of the plurality of keys. It is preferable to be disposed
toward the center of the inner space.
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[0007]
In the electronic keyboard instrument according to the present invention, a keyboard, a musical
tone signal generation circuit for generating a musical tone signal according to the operation of
the keyboard, and at least one speaker for emitting a musical tone signal generated by the
musical tone signal generation circuit. A housing configured to receive the at least one speaker
and the circuit component in the inner space and to support the keyboard with the playing
portion exposed, and the inner space of the housing And at least one resonator body having an
open part partially open, wherein the housing is a part of the lower part divided by a shelf board
on which the keyboard is mounted as an internal space thereof. A first chamber on the side and a
second chamber on the upper side are defined, and the housing is provided with a sound
emission path for transmitting the sound emitted from the at least one speaker to the outside of
the housing. Configured and said sound emission The first sound emission path emitted to the
outside directly from the sound emission surface of the at least one speaker, and the at least one
sound emitted from the at least one speaker above the keyboard of the second room The at least
one resonator includes a second sound emission path propagating through the sound hole to the
outside of the housing, and the at least one resonance body eigen vibration at a frequency
generated in the inner space of the housing by driving the at least one speaker. The said open
part is arrange | positioned at the antinode of the sound pressure of this.
[0008]
The electronic keyboard instrument according to the present invention comprises a keyboard, a
musical tone signal generation circuit for generating a musical tone signal according to the
operation of the keyboard, and a key support member for supporting the keyboard and the
musical tone signal generation circuit from below. At least one speaker for emitting the musical
tone signal generated by the musical tone signal generation circuit, a speaker box disposed below
the key support member and accommodating the at least one speaker in an internal space, and
an inside of the speaker box The at least one resonator comprises at least one resonator disposed
in a space, the at least one resonator comprising a tubular body constituted by a closed end
closed at one longitudinal end and an open end opened at the other end. The at least one
resonator has a specific frequency of a specific frequency of the sound wave, the open end of
which generates a reaction force that suppresses vibration at the time of sound emission of at
least one speaker Located in the belly of the figure of the sound pressure, that resonate at the
particular frequency, wherein the nodes of the natural vibration mode of the sound pressure of
the specific frequency is to be located in said at least one speaker vicinity.
[0009]
In the acoustic adjustment system according to the present invention, an acoustic signal
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generation circuit that generates an acoustic signal, at least one speaker that emits an acoustic
signal generated by the acoustic signal generation circuit, and the at least one speaker in an
internal space And at least one resonating body disposed in the loudspeaker box, the at least one
resonating body having an open end portion for vibration at the time of sound emission of at
least one loudspeaker The sound pressure node of the specific vibration mode is located at the
antinode of the sound pressure of the natural vibration mode of the specific frequency of the
sound wave causing the reaction force to be restrained, and the node of the sound pressure of
the natural vibration mode of the specific frequency is the at least one. It is characterized in that
it is located near the speaker.
[0010]
According to the present invention, in an electronic keyboard instrument having a built-in
speaker, unnecessary resonance generated in the space behind the speaker in the housing can be
reduced.
[0011]
FIG. 2 is a perspective view showing the appearance of the electronic keyboard instrument
according to the first embodiment.
FIG. 2 is a perspective view of the electronic keyboard instrument according to the first
embodiment.
It is the figure which looked at the electronic keyboard instrument shown in FIG. 2 from the
upper surface.
FIG. 1 is a view showing a resonator according to a first embodiment.
(A)-(c) is an image figure showing the reverberation of the propagation sound of a 1st sound
emission path | route and a 2nd sound emission path | route. (A) And (b) is an image figure
showing the reverberation of the propagation sound of a 1st sound emission path | route and a
2nd sound emission path | route. (A) And (b) is a figure explaining the wavelength of the natural
oscillation mode of the housing | casing part which concerns on Embodiment 1. FIG. (A)-(c) is a
figure which shows the frequency characteristic in the case where a resonator is provided in
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Embodiment 1, and when not providing it. FIG. 7 is a perspective view of an electronic keyboard
instrument according to a second embodiment. It is a front view of the electronic keyboard
instrument shown in FIG. It is a figure of the state which removed the lower front plate of the
electronic keyboard instrument shown in FIG. It is sectional drawing of the electronic keyboard
musical instrument at the time of cut | disconnecting by cutting-line BB in FIG. FIG. 11 is a view
showing a lower front plate and a lower front plate of the electronic keyboard instrument shown
in FIG. 10 and a state in which the speaker is removed. FIG. 11 is a cross-sectional view of the
electronic keyboard instrument taken along the cutting line A-A in FIG. 10. (A) And (b) is a figure
explaining the position of the partition plate which concerns on Embodiment 2. FIG. It is a figure
which shows the listening sound pressure frequency characteristic in the player position at the
time of providing a partition plate in Embodiment 2. FIG. (A)-(d) is a figure showing the resonator
which concerns on Embodiment 2. FIG. FIG. 10 is a view for explaining the position of the
opening of the second resonator according to the second embodiment. It is a figure which shows
the listening sound pressure frequency characteristic for every installation pattern of a
resonance body about R part in FIG. It is a figure which shows the installation pattern of a
resonance body. FIG. 10 is a perspective view of an electronic keyboard instrument according to
a third embodiment. It is a front view of the electronic keyboard instrument shown in FIG. FIG.
22 is a cross-sectional view of the electronic keyboard instrument taken along a cutting line XXIIXXII in FIG. 21. It is a figure which shows the position of the speaker in a speaker box, and the
arrangement position of a resonance body. It is a figure which shows the mode of the sound
pressure in case the resonator is not arrange | positioned in a speaker box. It is a figure which
shows the mode of the sound pressure at the time of arrange | positioning a resonator in a
speaker box. It is a figure which shows the mode of the sound pressure at the time of arrange |
positioning a resonator in a speaker box. It is a figure which shows the mode of the sound
pressure in case the resonator is not arrange | positioned in a speaker box. It is a figure which
shows the mode of the sound pressure at the time of arrange | positioning a resonator in a
speaker box. It is a figure which shows the mode of the sound pressure at the time of arrange |
positioning a resonator in a speaker box. (A) And (b) is the simplification figure which looked at
the internal space of the housing | casing part which concerns on the modification 1 from an
upper surface. (A)-(d) are the simplified figures which looked at the internal space of the housing
| casing part which concerns on the modification 2 from the front. (A)-(c) is a figure explaining
the shape of the housing | casing part of the electronic keyboard musical instrument which
concerns on the modification 3. FIG.
(A) is a figure showing typically the appearance of the board vibration resonance object
concerning modification 4. (B) is sectional drawing which looked at a board vibration resonance
body from arrow VI-VI in (a). (A) is a figure which represented typically the external appearance
of the Helmholtz resonator which concerns on modification 4. FIG. (B) is a cross-sectional view of
the Helmholtz resonator seen from arrows VIII-VIII in (a). (A) is a figure which represented
typically the external appearance of the resonance body which concerns on modification 4. FIG.
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(B) is sectional drawing which looked at a resonator from arrow II-II in (a). (A)-(d2) is a figure
showing the tubular resonant body which has an adjustment mechanism which concerns on
modification 5. FIG. (A) And (b) is a figure showing the Helmholtz resonator which has an
adjustment mechanism which concerns on modification 5. FIG. (A) is a figure which shows the
example of installation of the partition and resonance body which concerns on modification 6.
FIG. (B) is a figure which represented the external appearance of a partition and a resonance
body typically. FIG. 18 is a diagram showing an electronic keyboard instrument according to a
modified example 7; (A)-(c) is a figure which shows the example of installation of the speaker in
the internal space of the housing | casing part which concerns on Embodiment 2, and a
resonance body.
[0012]
First Embodiment FIG. 1 is a perspective view showing an appearance of an electronic keyboard
instrument according to the present embodiment. As shown in this figure, the electronic
keyboard instrument 1 has a keyboard unit 2, a housing unit 3 for supporting the keyboard unit
2, and a pedal unit 4 provided near the lower center of the housing unit 3. The keyboard unit 2 is
provided on the front side of the drawing (the player side), and has a plate-like mouthpiece
portion 14 extending in the horizontal direction and plate-like armwood portions 13 and 13
extending to the back from both ends of the mouthpiece 14. And a shelf board 19 (see FIG. 3)
provided so as to cover the bottom of the U-shaped frame formed by the mouthpiece portion 14
and the arms 13 and 13. A keyboard 11 in which white keys and black keys are arranged is
accommodated in a frame formed by the arm-and-wood parts 13 and 13, the stick 14 and the
shelf plate 19 so as to cover the upper part on the back side of the keyboard 11. An operation
panel 12 including a power switch and various operation switches is provided. A front plate 11a
(a front side surface) which is a side surface of the front (player side) of the electronic keyboard
instrument 1 is provided above the keyboard 11. The front plate 11a has a tone escapement
described later. 17a (sound output hole) is formed. Further, a keyboard lid 15 covering the
keyboard 11 is provided, and the keyboard lid 15 is configured to be able to be pulled out to the
player side by the slide mechanism 151, and covers the keyboard 11 in a state of being pulled
out to the end by the player side It has become. In the state shown in FIG. 1, the keyboard lid 15
is pulled back to the back side (opposite to the player), whereby the playing portion of the
keyboard 11 is exposed. Each key of the keyboard 11 is provided with a detection switch (not
shown) for detecting the key pressed by the player. The detection switch outputs an operation
signal corresponding to the detected key to a tone signal detection circuit to be described later.
[0013]
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The housing 3 has vertically extending side plates 18 and 18 respectively supporting the left and
right ends of the keyboard unit 2. The lower ends of the side plates 18 and 18 are connected by
the bottom member 21, and the upper ends of the side plates 18 and 18 are connected by a
plate-like roof plate 17. The roof plate 17 covers the upper portion of the electronic keyboard
instrument 1 so as to conform to the upper shape of the side plates 18. The back sides of the side
plates 18, 18, the roof plate 17 and the shelf plate 19 are covered by a back plate portion (not
shown). From around the bottom of the side plates 18, 18, the buttocks 22, 22 are provided so as
to protrude toward the player side, and the case 3 is made to stand stably by this buttocks 22. A
music score plate 16 is provided on the central upper surface of the roof plate 17, and a plurality
of tone escapes 17 a (broken line frame) provided in the width direction are formed near the
upper portion of the keyboard lid 15. Hereinafter, 17a is referred to as an acoustic relief or TE.
The acoustic relief portion 17a comprises an escape hole and a saran net covering the outer
surface thereof. The TE may be made of only the acoustic relief hole (without saran net). In the
above-described configuration, a space partitioned by the mouth rod portion 14, the shelf plate
19, the arm portion 13, the side plate 18, the roof plate 17, the back plate portion, the keyboard
11, and the operation panel 12 is configured. Although this space has a property close to a
substantially closed space, air can be moved in and out from the space between the keys of the
TE 17a and the keyboard 11 and the like. The pedal unit 4 is housed in the central portion of the
bottom member 21 with the pedal protruding toward the player.
[0014]
Next, the details of the housing unit 3 will be described. FIG. 2 is a perspective view of the
electronic keyboard instrument 1 shown in FIG. 1 with the keyboard lid 15 covering the
keyboard 11 and the roof plate 17 removed. FIG. 3 shows the electronic keyboard instrument 1
shown in FIG. It is the figure seen from the upper surface. As shown in FIGS. 2 and 3, in the
internal space of the housing 3, two speakers 30 (30a, 30b) for emitting a tone signal are
provided. The speaker 30 is attached so that the sound emitting surface faces downward, and the
shelf board 19 at a position corresponding to the sound emitting surface is provided with a hole
for sound emission. The sound emitted from the speaker 30 is transmitted to the player through
the sound emission hole. This propagation path is hereinafter referred to as a first sound
emission path (broken line arrow W1 in FIG. 1). Further, in a state where the operation part of
the keyboard 11 is exposed, the sound emitted from behind the sound emitting surface of the
speaker 30 passes through the internal space of the housing 3 and the TE 17a provided on the
roof plate 17 and the keyboard It propagates to the player's side from the gap between the key in
11 and the key. This propagation path is hereinafter referred to as a second sound emission path
(broken line arrow W2 in FIG. 1).
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[0015]
In the internal space of the housing unit 3, four resonators (resonators) 32 (32a, 32b) configured
in a rectangular tube shape, and a musical tone signal for generating a musical tone signal based
on an operation signal indicating a depressed key A circuit board 34 such as a generation circuit
is provided. Further, at least one circuit component is provided in the internal space of the
housing 3. Here, the resonator 32 according to the present embodiment will be described with
reference to FIG. FIG. 4 is a view showing a resonator 32 which is an example of a resonator
according to the present embodiment. The left view of FIG. 4 is a view schematically showing the
appearance of the resonator 32. The resonator 32 is formed into a tubular shape, for example, a
formed body formed of a cardboard or a pulp mold or a material such as metal or synthetic resin.
It is a resonant tube formed in The resonator 32 has an opening (opening) 321 (control point) in
which one end in the longitudinal direction is opened, a hollow region 322 communicating with
the opening 321, and a closed part 323 in which the other end is closed. And. The resonator 32
is an example of a tubular body of which a part is an open end (opening 321) as an open part
and the other end is a closed end (closing part 323). The hollow region 322 of each resonator 32
has the same length L. As shown in FIG. 4, the diameter of the resonator 32 is smaller than the
distance between the opening 321 (open end) and the closed part 321 (closed end). The vicinity
of the opening 321 of the resonator 32 may be closed with a flow resistant material having air
permeability such as glass wool, cloth, sponge, gauze, etc. and having flow resistance, or urethane
foam rubber The material may be closed with a flow resistant material having a vented structure.
In addition, only the opening may be formed narrowly with these flow resistance materials.
[0016]
Referring back to FIGS. 2 and 3, the description will be continued. The resonator 32 is a fixture
such that the longitudinal surface of the resonator 32 is in contact with the surface of the back
plate 20 in the internal space of the housing 3 and is positioned outside the position where the
speaker 30 is provided. And is fixed by an adhesive or the like. The two resonators 32a are
arranged such that the openings 321 are directed in the direction of the arrows L and R, that is,
toward the outside of the housing, and the two resonators 32b are arranged in the directions of
the arrows L The direction and the R direction, that is, facing each other, are directed to the
inside of the housing. That is, the resonators 32 a and 32 b are arranged such that the axes
thereof are parallel to the arrangement direction in which the plurality of keys are arranged in
the internal space of the housing 3.
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[0017]
By the way, the TE 17a is provided to enhance the sound image of the tone corresponding to the
operation of the keyboard 11. As shown in FIG. 5 (a), the second sound emission path (broken
line in FIG. 1) from the reverberation A of the sound of each keyboard originally transmitted from
the first sound emission path (broken line arrow W1 in FIG. 1). It is desirable that the magnitude
and length of the reverberation B of the sound of each keyboard transmitted from the arrow W2)
be small. For example, as shown in FIGS. 5 (b) and 5 (c), when the reverberation B is larger or
longer than the reverberation A, the reverberation A is erased by the reverberation B, and the
sound is scattered or the keyboard is used. Cause the balance of the volume of the When the
frequency characteristic of the musical tone signal input to the speaker 30 is adjusted before
amplification using a digital equalizer, as shown in FIG. 6A, reverberation A and reverberation B
before adjustment are reverberation A 'and reverberation. Although adjusted to B ', the slope of
the reverberation B does not change only by reducing the sound pressure levels of the
reverberation A and the reverberation B entirely.
[0018]
In the present embodiment, by providing the above-described resonator 32, as shown in FIG. 6B,
the slope of the reverberation A is not changed, and the slope of the reverberation B is adjusted
to be smaller and shorter than the reverberation A. . Specifically, among the natural vibration
modes of the resonance frequency in the internal space of the housing 3, the reverberation of the
sound of the resonance frequency excited by the driving of the speaker 30 is in the state shown
in FIG. 6 (b). Then, the resonator 32 is provided at the antinode of the sound pressure of the
natural vibration mode of the resonance frequency.
[0019]
Here, the operation of reducing the sound pressure by the resonator 32 will be described. When
a sound wave from the internal space of the housing 3 enters the opening 321 of the resonator
32 shown in the left view of FIG. 4, the sound wave enters the hollow region 322 from the
opening 321 and is reflected by the closed part 323 The sound wave of a wavelength equivalent
to four times the length L of the hollow region 322 at this time generates the natural vibration
state SW, as shown in the right figure of FIG. While the vibration is repeated, the friction on the
inner wall surface of the resonator 32, the viscous action between gas molecules at the opening
321, and the sound wave delayed by half wavelength (= half cycle) for the sound wave of the
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resonance frequency of the resonator are emitted from the resonator The acoustic energy is
consumed by the phase interference action which continues to be performed, one or both of
these two actions, and the sound pressure is reduced in the vicinity of the opening 321 around
this wavelength. The resonator 32 is arranged such that the hollow region 322 is connected to a
space to which sound is to be attenuated, so that the sound in the space enters the opening 321
of the resonator 32, and the resonator 32 resonates. Reduce the sound pressure in the vicinity.
[0020]
For example, when the width of the housing 3 in the key arrangement direction (hereinafter
referred to as the width of the housing 3) is about 1300 mm (more in the case of 88 keys), for
example, 280 to 340 Hz It is experimentally obtained that the frequency (corresponding to the
C3 to F3 keyboard tone) is excited. Therefore, in order to reduce the sound pressure of 280 to
340 Hz excited in the internal space of the housing portion 3, the length of the hollow region
322 of the resonator 32 is 1/4 of the wavelength of the sound wave of the frequency band. It
should be set to
[0021]
Here, the natural vibration mode generated in the internal space of the housing 3 will be
described. The natural frequency fN in the closed hollow rectangular solid is the natural
frequency fN when the length in the x-axis direction is Lx, the length in the y-axis direction is Ly,
and the length in the z-axis direction is Lz. These satisfy the relationship of the following formula
(1). In equation (1), c0 represents the speed of sound, and nx, ny and nz are values representing
the order of the natural vibration mode, and are arbitrary integers of “0” or more.
[0022]
In the rectangular parallelepiped internal space, natural frequencies exist for any combination of
the values of the orders nx, ny and nz. The eigenfrequency obtained as “0” of “nx”, “ny”,
and “nz” as “0” according to equation (1) is a eigenfrequency of the one-dimensional mode.
This natural frequency corresponds to the frequency of the natural vibration mode parallel to
one axis in the inner space. The natural frequency for which one of nx, ny and nz is "0" is a
natural frequency of the two-dimensional mode. The natural frequency corresponds to the
frequency of a natural vibration mode that is obliquely incident on the other two pairs of wall
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surfaces in parallel with a pair of parallel wall surfaces in the inner space. The natural frequency
which is not "0" in any of nx, ny and nz is the natural frequency of the three-dimensional mode.
This natural frequency corresponds to the frequency of the natural vibration mode obliquely
incident on all the wall surfaces in the internal space of the rectangular parallelepiped.
[0023]
The natural frequency of the second order (nx = 2) of the one-dimensional mode in the state in
which the casing 3 is sealed, that is, when the TE 17a or the like is not provided is 250 Hz from
the above equation (1). This is the frequency of the wavelength corresponding to the width of the
housing 3. The 280 to 340 Hz obtained by the experiment is 15 to 30% higher than this
frequency, and has a shorter wavelength than the closed state. The inventors considered that this
is due to the influence of the sound emission path such as the space between the keys of the TE
17 a and the keyboard 11 in the housing 3. For example, in the case of an acoustic tube M
having an opening v1 and a hollow area v2 as shown in FIG. 7 (a), when the opening v1 is
extremely small with respect to the hollow area v2, it is similar to a double closed pipe. (B) As
shown in (i), the wavelength of the primary natural vibration mode in the acoustic pipe M is 1⁄2
wavelength. Further, when the opening v1 of the acoustic tube M is extremely large relative to
the hollow region v2, it is similar to the one-sided open tube, and as shown in FIG. 7 (b) (iii), the
primary characteristic in the acoustic tube M The wavelength of the vibration mode is 3⁄4
wavelength, and the wavelength is shorter than that in FIG. 7 (b) (i). The same applies to the
secondary case. In the case of the casing 3 provided with the TE 17a etc., as can be understood
from the experimental results, an intermediate FIG. 7 (b) (i) of FIG. 7 (b) (i) and FIG. 7 (b) (iii) It
becomes a wavelength shown to ii). That is, it is considered that the wavelength is shorter than in
the case of the double closed tube, and the wavelength is longer than in the case of the single
open tube.
[0024]
In the internal space of the housing 3, since the two speakers 30 are driven in phase, the natural
frequencies of the second and fourth natural vibration modes in which the nodes of the sound
pressure in the internal space are even are particularly easily excited. The natural frequency of
the first-order eigenmode in which the nodes of the sound pressure become one is difficult to
excite. Therefore, the resonator 32 may be designed to have a length of 1⁄4 of the wavelength of
the specific frequency which is 15 to 30% higher than the frequency of the wavelength
equivalent to the width of the housing 3. In addition, in the internal space of the housing 3, the
resonator 32 is disposed such that the opening 321 (control point) of the resonator 32 is located
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in at least one of the antinodes of the sound pressure of the specific vibration mode. As a result,
the sound pressure of a specific frequency (280 to 340 Hz in this example) of the sound
generated in the internal space when the sound due to the sound emission of the speaker 30 is
generated is reduced.
[0025]
FIG. 8A is a diagram showing frequency characteristics in the internal space in the case where
the resonator 32 designed as described above is provided in the internal space of the casing 3
and in the case where the resonator 32 is not provided. FIG. 8B shows the frequency
characteristics at the position of the player when the resonator 32 is provided in the internal
space of the housing 3 and when the resonator 32 is not provided. The solid lines in FIGS. 8A and
8B indicate frequency characteristics when the resonator 32 is not provided in the inner space,
and it can be seen that excitation is performed at a frequency of 280 to 340 Hz. The broken lines
in FIGS. 8A and 8B indicate the frequency characteristics when the resonator 32 is provided in
the inner space, and the sound pressure at 280 to 340 Hz is reduced by the provision of the
resonator 32. Moreover, FIG.8 (c) is the figure which showed the sound pressure change of the
sound of 280-340 Hz in the case where it does not provide with the case where resonator 32 is
provided in the internal space of the housing | casing part 3. FIG. In FIG. 8C, the solid line shows
the frequency characteristic when the resonator 32 is not provided in the internal space, and the
broken line shows the frequency characteristic when the resonator 32 is provided in the internal
space. According to this figure, by providing the resonator 32, as a result of suppressing
unnecessary resonance, since the peak position shifts forward, the rising of the sound is
quickened and the sound can be heard clearly.
[0026]
In the embodiment described above, the resonator 32 is located at a position outside the position
where the speaker 30 is provided in the internal space of the housing 3 and which is the
antinode of the sound pressure of the specific vibration style. An example in which four
resonators 32 are provided so as to locate the opening 321 is shown in FIGS. In this example, a
natural vibration mode of a wavelength substantially equal to the length of the key arrangement
direction of the housing 3 is generated, and a positive antinode of the sound pressure of the
natural vibration mode of the frequency to be controlled whose sound pressure should be
reduced Since the negative antinodes of the sound pressure are located near the center at the
both ends of the body part 3, the openings (control points) 321 of the four resonators 32 are
provided at positions corresponding to both antinodes. So configured. Thus, the sound pressure
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of the frequency may be reduced by providing the openings 321 of the resonator 32 at all
antinode positions of the sound pressure of the natural vibration mode of the frequency to be
controlled. The opening 321 of the resonator 32 may be provided at the place of the sound
pressure belly. That is, the two resonators 32b near the center may be removed from the four
resonators 32 shown in FIG. 2, or only the resonators 32a at both ends excluding the two
resonators 32b near the center may be arranged. May be Alternatively, only one resonator of one
of the resonators 32b near the center shown in FIG. 2 may be disposed. In other words, the
opening 321 of the resonator 32 resonating at the frequency may be located at least one of the
antinodes of the sound pressure of the natural vibration mode at the frequency to be controlled.
Even in such a case, the sound pressure can be reduced as compared with the case where the
resonator 32 is not provided. As can be seen from the above, when the acoustic characteristics
are distorted or the frequency characteristics to be emphasized in particular are to be raised or
lowered depending on the conditions of the case (shape and arrangement of obstacles (electronic
components such as power supply) in the case) In addition, it is possible to produce a housing
having acoustic characteristics in accordance with the designer's intention to a certain extent by
arranging a resonator of a position and length according to the frequency.
[0027]
Second Embodiment FIG. 9 shows a perspective view of an electronic keyboard instrument
according to the present embodiment. The electronic keyboard instrument 1A has a keyboard
unit 2A and a housing 3A for supporting the keyboard unit 2A. The keyboard unit 2A includes a
horizontally extending plate-like mouth rod portion 44, plate-like side plates 48 and 48
extending to the back from both ends of the mouth rod portion 44, the mouth rod portion 44 and
the side plates 48 and 48. A shelf plate 53 (see FIG. 12) is provided to cover the bottom of the Ushaped frame. A keyboard 41 in which a white key and a black key are arranged is disposed in a
frame formed by the side plates 48 and 48, the stick portion 44 and the shelf plate 53. In
addition to covering the back side of the keyboard 41, a keyboard cover 45 is rotatably provided,
and a power switch and various operation switches are provided in the time-piece 42. When the
keyboard lid 45 is opened so that the keyboard 41 can be seen, the surface of the keyboard lid
45 visible to the player has a music score holder 46 and a lid front 451, and the keyboard lid 45
has the keyboard lid 45 on the player side. The keyboard 41 is covered in the state of being
pivoted to the position shown in FIG. 9, and the playing part of the keyboard 41 is exposed in the
state shown in FIG. Each key of the keyboard 41 is provided with a detection switch (not shown)
for detecting the key pressed by the player. The detection switch outputs an operation signal
corresponding to the detected key to a tone signal detection circuit to be described later.
[0028]
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14
The housing portion 3A has vertically extending arm portions 43, 43 respectively supporting the
left and right end portions of the keyboard unit 2A. The lower end portions of the side plates 48,
48 on the rear side of the arm wood portion 43 are connected by a plate-like bottom plate 54
(see FIG. 12), and the upper ends of the side plates 48, 48 are connected by a plate-like roof plate
47. It is done. The back sides of the side plates 48 and 48 and the roof plate 47 are covered by a
back plate (not shown). The front plate 49 is attached so as to cover from the upper end of the
roof plate 47 to the rear portion of the keyboard, and a TE 49a (broken line frame) is provided
on the upper portion of the front plate 49. Also, the lower front upper plate 52a and the lower
lower front plate 52b are attached so as to cover from the bottom surface of the shelf plate 53 to
the lower end portion of the bottom plate 54. On the lower front plate 52a, sound emission holes
for emitting musical tones from the speaker 60 and saran nets 51a and 51b are provided at
positions corresponding to the speaker 60 (see FIG. 12). Further, front legs 50, 50 are provided
so as to project to the player side from near the bottoms of the arm wooden parts 43, 43, and the
housing 3A is stably stood by this front legs. . The pedal unit 4A is accommodated at the center
of the lower front lower plate 52b in a state where the respective pedals project toward the
player. In the above-described configuration, a space is defined by the roof plate 47, the side
plate 48, the upper front plate 49, the back plate 55, the keyboard 41, the lower front plate 52a,
the lower front plate 52b, and the bottom plate 54. This space has a property close to a
substantially closed space as in the first embodiment, but air can enter and exit from the space
between the keys of the TE 49a and the keyboard 41 and the like.
[0029]
Here, the internal structure of the housing 3A will be described. 10 is a front view of the
electronic keyboard instrument 1A shown in FIG. 9, and FIG. 11 is a view of the electronic
keyboard instrument 1A shown in FIG. 10 from which the lower front plate 52a is removed. FIG.
12 is a cross-sectional view of the electronic keyboard instrument 1A in the case of being cut
along the cutting line B-B in FIG.
[0030]
As shown in FIG. 12, the shelf board 53 is supported by the front leg 50, the lower front board
52 a, the lower front board 52 b, and the side board 48. An acoustic passage space P is provided
between the shelf plate 53 and the back plate 55. The internal space of the housing 3A is an
acoustic passage space above the shelf plate 53 (hereinafter referred to as the upper internal
16-04-2019
15
space S1) and an acoustic passage space (hereinafter referred to as the lower internal space S2)
in which the speakers 60a and 60b are provided. Is connected via the acoustic passage space P
between the shelf plate 53 and the back plate 55. That is, as the internal space, the housing 3A is
a lower internal space S2 (first chamber) and an upper internal space S1 (second chamber) which
are partially partitioned by the shelf board 53 on which the keyboard 41 is placed. And are
defined. As shown in FIG. 12, the width of the acoustic passage space P in the depth direction is
narrower than the upper internal space S1 and the lower internal space S2. The internal space of
the housing 3A is more complicated than the simple rectangular structure as in the structure of
the housing 3 described in the first embodiment. Further, as shown in FIG. 12, baffle plates 61
(61a, 61b) to which the speakers 60 (60a, 60b) are attached are provided at the lower front plate
52a of the housing 3A. Under the shelf plate 53 in the internal space of the housing portion 3A, a
partition plate for partitioning from the lower surface of the shelf plate 53 to the bottom plate 54
so that the speakers 60a and 60b are provided spatially independently in the key arrangement
direction. 70 (70a, 70b) are provided (see FIGS. 11 and 12). The speaker 60 is attached so that
the sound emitting surface faces the player, and a hole 62 for sound emission is provided on the
lower front plate 52a at a position corresponding to the sound emitting surface. The sound
emitted from the speaker 60 is transmitted to the player through the hole 62 (first sound
emission path W1). Further, the sound emitted from behind the sound emitting surface of the
speaker 60 propagates from the lower internal space S2 to the upper internal space S1 via the
narrowed acoustic passage space P, and the TE 49a provided on the front plate 49 and The
sound is propagated to the player from the gap between the keys on the keyboard 41 (second
sound emission path W2).
[0031]
Further, FIG. 13 shows a state in which the upper lower plate 52a and the lower lower plate 52b
of the electronic keyboard instrument 1A and the baffle plate 61 to which the speaker 60 is
attached are removed. As shown in this figure, a circuit board 90 such as a tone signal generation
circuit or a tone generator circuit and a pedal unit 4A are installed in the space between the
partition plate 70a and the partition plate 70b. Further, among the spaces partitioned by the
partition plates 70a and 70b provided in the lower side internal space S2, each of the spaces
provided with the speakers 60a and 60b (hereinafter referred to as a speaker installation space)
Resonant bodies 80 each consisting of a first resonator 80a and a second resonator 80b are
installed in each. Here, FIG. 14 shows a cross-sectional view of the electronic keyboard
instrument 1A when it is cut along the cutting line A-A in FIG. As shown in this figure, the
respective resonators 80 are provided at positions outside the lower inner space S2 from the
position of the speaker 60.
16-04-2019
16
[0032]
Here, the positions at which the partition plates 70a and 70b are provided will be described. The
internal space of the housing 3A of the electronic keyboard instrument 1A according to the
present embodiment is longer in the height direction than the internal space of the housing 3 of
the electronic keyboard instrument 1 according to the first embodiment. . Therefore, a twodimensional natural vibration mode in the height direction and the arrangement direction of the
keys is generated in the internal space of the housing 3A, and the natural vibration mode excited
by the driving of the speaker becomes larger than the case of the first embodiment.
[0033]
The housing 3A shown in FIG. 15A is a simplified view of the internal space of the housing 3A in
a state in which the partition plate 70 is not provided, as viewed from the front. As shown in this
figure, when, for example, the fourth-order natural vibration state SW2 is generated in the key
arrangement direction, it is assumed that the positions of the speakers 60a and 60b are locations
of the sound pressure of the natural vibration state SW2. The speaker 60 easily vibrates and its
natural vibration state SW2 is easily excited. On the other hand, as shown in FIG. 15B, by
providing the partition plates 70a and 70b such that the positions of the speakers 60a and 60b
become the positions of the nodes of the sound pressure of the natural vibration mode SW2, the
vibration of the speaker 60 makes it unique. The vibration state SW2 is less likely to be excited.
The position at which the speaker 60 is attached is restricted by the size of the electronic
component provided in the internal space of the housing 3A, the size of the housing 3A, and the
like, so it is difficult to easily change the position of the speaker. Therefore, in the case 3A
according to the present embodiment, the position of the sound pressure node of the natural
vibration mode generated in the internal space is adjusted by the partition plate 70, and the
number of natural vibration modes excited by the vibration of the speaker 60 is calculated. It is
reduced.
[0034]
The listening sound pressure frequency characteristics at the player position when the partition
plate 70 is provided as described above are shown in FIG. A peak occurs in a portion indicated by
R1 in FIG. 16 and a dip occurs in a portion indicated by R2. The peak is a specific frequency
excited by the vibration of the speaker 60 (a frequency to be a broken line B in FIGS. 5B and 5C)
as in the first embodiment. The dip is considered to be caused by the reaction force that
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17
suppresses the vibration of the speaker 60. That is, the timing at which the diaphragm of the
speaker 60 tries to push air toward the internal space at a timing when the sound pressure
becomes positive in the space behind the sound emission surface of the speaker 60, or the timing
at which the sound pressure in the space behind becomes negative. It is considered that the
reaction force for pushing the air toward the external space acts on the diaphragm to suppress
the vibration.
[0035]
The resonators 80 provided in each speaker installation space of the housing 3A according to the
present embodiment are provided to suppress the peaks and dips shown in FIG. Here, the
structure of the resonator 80 according to the present embodiment will be described with
reference to FIG. FIG. 17 (a) is a perspective view showing the appearance of a resonator 80, and
FIG. 17 (b) is a plan view of the resonator 80 shown in FIG. 17 (a). 17C is a rear view of the
resonator 80, and FIG. 17D is a front view of the resonator 80.
[0036]
As shown in FIG. 17A, the resonator 80 is formed by attaching a cylindrical first resonator 80 a
and a second resonator 80 b to a mounting plate 81. Similar to the resonator 32 described in the
first embodiment, the first resonator 80a and the second resonator 80b are formed of a material
such as metal or synthetic resin in a tubular shape and have a hollow region. As shown in FIGS.
17B to 17D, the first resonator 80a and the second resonator 80b have openings (control points)
801a and 801b in which one end in the longitudinal direction is opened. And the other end has a
closing portion 811 a, 811 b closed by the mounting member 82.
[0037]
The first resonator 80a is an example of the resonator of the present invention. The first
resonator 80a has a function of reducing the sound pressure of a specific frequency excited by
the vibration of the speaker 60, that is, the function of suppressing the peak indicated by R1 in
FIG. The length of the hollow region of the first resonator 80a is designed to be 1/4 of the
wavelength of the sound wave of the frequency at which the peak occurs.
16-04-2019
18
[0038]
The second resonator 80b is an example of the second resonator of the present invention. The
second resonator 80b has a function of releasing a reaction force that suppresses the vibration of
the speaker 60, that is, a function of suppressing the dip shown by R2 in FIG. The length of the
hollow region of the second resonator 80b is designed to be 1/4 the wavelength of the sound
wave at the frequency at which the dip occurs.
[0039]
The location where the opening 801a of the first resonator 80a is located in each speaker
installation space is the location of the antinode of the sound pressure of the natural vibration
style of the frequency at which the peak occurs, as in the first embodiment. In each speaker
installation space, the opening 801b of the second resonator 80b is located at the center of the
speaker 60 (the voice coil of the speaker by a distance of approximately 1⁄4 of the wavelength of
the sound wave of the frequency at which dip occurs). On the boundary plane away from the The
opening 801 b of the second resonator 80 b is an antinode of the sound pressure of the natural
vibration mode of the frequency at which the dip occurs, and is a position near the baffle plate
61 to which the speaker 60 is attached. A sound wave containing the frequency enters the
hollow region 801 b from the opening 801 b of the second resonator 80 b, so that the second
resonator 80 b resonates, and the sound pressure is reduced around the frequency near the
opening 801 b. Reaction force is released. In each speaker installation space, the position where
the opening 801b of the second resonator 80b is located is, for example, the antinode of the
sound pressure of the natural vibration style in the speaker installation space of the frequency at
which dips occur in FIGS. Of the sound pressure node of the natural vibration mode of the
frequency at which the dip is generated by the resonance of the second resonator 80b at the
frequency at which the dip is generated. It can also be positioned near each position on the axial
center of the voice coil. Here, in the vicinity of the center of the speaker 60 where the node of the
sound pressure is located, it is desirable that the distance from the center of the speaker 60 be
within λ / 8, assuming that the wavelength λ of the sound wave of the frequency at which dip
occurs. . Thus, the reaction force of the speaker 60 is also released by locating the node of the
sound pressure of the natural vibration mode at the frequency at which the dip is generated
within the region within λ / 8 from the center of the speaker 60. is there.
[0040]
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19
When the TE 49a is provided above the keyboard 41 as in the electronic keyboard instrument 1A
according to the present embodiment, the opening 801a of the first resonator 80a is in the
lateral direction of each speaker installation space (key arrangement In the direction), the
position is closer to the side plate 48 than the position of the speaker 60, that is, the position
closer to the outside space, and the effect is further enhanced by installing near the center in the
height direction of each speaker installation space. Are obtained by experiment. In addition, the
opening 801b of the second resonator 80b is located on the bottom side of each speaker
installation space, that is, as in the lower internal space S2 shown in FIG. The inventors have
experimentally obtained that it is desirable to place the lower boundary surface at a distance of
about 1⁄4 of the wavelength of the sound wave of the frequency at which the force is generated.
Since the natural vibration mode in the housing 3A changes depending on the position where the
TE 49a is provided, etc., the positions of the openings of the first resonator 80a and the second
resonator 80b are adjusted by experiment etc. according to how the TE 49a is provided. Is
desirable.
[0041]
When only the first resonator 80a is installed in each speaker installation space of the lower
inner space S2 as shown in (A) of FIG. 19B (waveform A), the frequency characteristic shown in
FIG. 19A (B in FIG. When only the first resonator 80b is installed in each speaker installation
space of the lower inner space S2 (waveform B) as shown in), each speaker installation of the
lower inner space S2 as shown in (C) of FIG. 19B When the first resonator 80a and the second
resonator 80b are installed in the space (waveform C), the results measured by the inventors and
each of the lower inner space S2 as shown in FIG. 19B (D) FIG. 16 shows the frequency
characteristics when the first resonator 80a and the second resonator 80b are not installed in the
speaker installation space (waveform D: similar to FIG. 16), and a portion including R1 and R2 in
FIG. It is an enlarged one.
[0042]
As shown in FIG. 19A, in the portion where dip occurs, as shown by the waveform B in which
only the second resonator 80b is installed, the speakers 60a and 60b are compared to the case
where the resonator 80 is not inserted. The reaction force for suppressing the vibration of the is
released, and the sound pressure of the sound wave of the frequency at which the dip has
occurred is rising.
Further, as shown by the waveform A in which only the first resonator 80a is installed, the sound
pressure of the excited frequency is higher than that in the case where the resonator 80 is not
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20
installed in the portion where the peak is generated. It has been reduced. When the first
resonator 80a and the second resonator 80b are installed as shown by the waveform C, the
sound pressure at the dip portion is higher than that of the waveform B, and the peak is higher
than that of the waveform A. The sound pressure of the portion is reduced, and the effect is
enhanced by installing the first resonator 80a and the second resonator 80b.
[0043]
As in the case of the electronic keyboard instrument 1A according to the present embodiment, in
the case of the housing 3A in which a two-dimensional natural vibration mode can occur, the
partition plate 70 is set so that the position of the speaker 60 becomes a node of sound pressure
in the natural vibration mode. By providing them, it is possible to reduce the natural vibration
state excited by the vibration of the speaker 60. Further, by providing the resonator 80 in each
speaker installation space, the sound pressure of the frequency can be reduced by the first
resonator 80 a resonating at the frequency being excited, and the reaction force for suppressing
the vibration of the speaker 60 The second resonator 80b resonates at the frequency causing the
noise to release the reaction force to increase the sound pressure of the frequency.
[0044]
Further, in the above-described embodiment, the opening 801 b of the second resonator 80 b
resonating at a frequency that generates a reaction force to the vibration of the speaker 60 is
moved downward from the center of the speaker 60 by 1⁄4 of the wavelength of the sound wave
of that frequency. An example is described in which the dip is reduced by providing the sensor at
a position away from the sound pressure, but the sound pressure of the natural vibration mode
of the frequency at which the dip is generated is a node near the TE 49a as the cause of the dip
The situation is conceivable. That is, although the natural vibration mode of the frequency at
which the dip is generated is excited by the vibration of the speaker 60, the sound pressure in
the vicinity of the TE 49a becomes weak and the volume emitted from the TE 49a becomes small.
Therefore, in such a case, the position of the node of the natural vibration mode in the internal
space of the housing portion 3A is such that the vicinity of the TE 49a is the antinode of the
sound pressure of the natural vibration mode of the frequency where dip occurs. The opening of
the second resonator 80b resonating at the frequency may be provided. With this configuration,
the position of the node in the natural vibration mode is forcibly generated by the opening 801b
of the second resonator 80b, the sound pressure near the TE 49a is controlled to the antinode,
and the frequency at which the dip occurs Sound pressure can be raised. In this case, the second
resonator 80b functions as a third resonator according to the present invention.
16-04-2019
21
[0045]
Third Embodiment FIG. 20 shows a perspective view of an electronic keyboard instrument
according to the present embodiment. The electronic keyboard instrument 501A has a housing
503A supporting the keyboard unit 502A and the keyboard unit 502A (see FIG. 22). The
keyboard unit 502A includes a horizontally extending plate-like mouth rod portion 544, platelike side plates 548 and 548 extending to the back from both ends of the mouth rod portion 544,
a mouth rod portion 544 and side plates 548 and 548. A shelf plate 553 (key support member)
is provided to cover the bottom of the U-shaped frame. A keyboard 541 in which a white key and
a black key are arranged is disposed in a frame formed by the side plates 548 and 548, the
mouthpiece portion 544 and the shelf plate 553. Further, the back side of the keyboard 541 is
covered, and the keyboard lid 545 is rotatably received, and a power switch and various
operation switches are provided on the time plate 542. When the keyboard lid 545 is opened so
that the keyboard 541 can be seen, the surface of the keyboard lid 545 visible to the player has a
music score holder 546 and a lid front 551, and the keyboard lid 545 is turned toward the player
In the state, the keyboard 541 is covered, and in the state shown in FIG. 20, the playing portion
of the keyboard 541 is exposed. Each key of the keyboard 541 is provided with a detection
switch (not shown) for detecting the key pressed by the player. The detection switch outputs an
operation signal corresponding to the detected key to a tone signal detection circuit 534
described later.
[0046]
The housing portion 503A has vertically extending arm portions 543 and 543 for supporting the
left and right sides of the keyboard unit 502A. The lower ends of the side plates 548, 548 on the
rear side of the arm wood portion 543 are connected by a plate-like bottom plate 547 (see FIG.
22), and the upper ends of the side plates 548, 548 are connected by a plate-like roof plate 547.
It is done. The side plates 548 and 548 and the back side of the roof plate 547 are covered by a
back plate (not shown). The front plate 549 is attached so as to cover from the upper end of the
roof plate 547 to the rear of the keyboard. Further, the shelf 553 is supported from below by the
front legs 550, 550. The musical tone signal detection circuit 534 is disposed inside the housing
503A. Under the shelf plate 553, a speaker box 580 is installed. The speaker box 580 is fixed to
the left and right side plates 548, 548, and is installed so that the front plate 581 of the speaker
box 580 does not project forward from the front end of the side plate 548. An inner space 582 of
the speaker box 580 is divided into two in the left-right direction by a partition plate 570, and
each is set as an inner space 582a, 582b (see FIG. 23). In the internal spaces 582a and 582b of
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22
the speaker box 580, the back portions of the later-described speakers 560a and 560b are
located. Further, on the front plate 581, sound emission holes for emitting the musical tone from
the speaker 560 and saran nets 551a and 551b are provided at positions corresponding to the
speaker 560, respectively. A TE 581a is provided above the portion where the saran nets 551a
and 551b of the front plate 581 are disposed. The internal space 582a of the speaker box 580
has a property close to a substantially closed space, but allows air to enter and exit from the
outside through the TE 581a. Therefore, the sound emitted from behind the sound emitting
surface of the speaker 560 is led to the outside through the TE 581a via the internal space 582a.
Below the speaker box 580, a lower front plate 552b is provided. The lower front plate 552 b
extends downward so as to be substantially flush with the front plate 581 of the speaker box
580. Further, front legs 550, 550 are provided so as to protrude from the bottom of the arm
wood parts 543, 543 to the player side, and the housing 503A is stably stood by this front leg. .
The pedal unit 504A is housed at the center of the lower front plate 552b, with the pedals
projecting toward the player.
[0047]
Here, the internal structure of the housing 503A will be described. 21 is a front view of the
electronic keyboard instrument 501A shown in FIG. 20, and FIG. 22 is a cross-sectional view of
the electronic keyboard instrument 501A in the case of being cut along the cutting line XXII-XXII
in FIG.
[0048]
The speaker 560 is attached such that the sound emission surface faces the player, and the front
plate 581 at a position corresponding to the sound emission surface is provided with a hole 562
for sound emission. The sound emitted from the speaker 560 is transmitted to the player
through the hole 562 (third sound emission path W3). In addition, the sound emitted from the
back of the speaker 560 is transmitted to the player side through the TE 581a provided on the
front plate 581 via the internal space 582a of the speaker box 580 (fourth sound emission path
W4 ).
[0049]
FIG. 23 is a diagram for describing the position of the speaker 560 in the internal space 582 of
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23
the speaker box 580 and the arrangement position of the resonator 590. The resonator 590 is
composed of a cylindrical third resonator 590a (an example of a second resonator) and a fourth
resonator 590b (an example of a second resonator), each of which is fixed to the wall of the
speaker box 580 Are disposed in the inner spaces 582a and 582b. In addition, the third
resonator 590a and the fourth resonator 590b have openings 591a and 591b (open ends) whose
one end in the longitudinal direction is open, and a closing part whose other end is closed. Each
has 592a, 592b (closed end).
[0050]
The third resonator 590a has a function of reducing the sound pressure of a specific frequency
excited by the vibration of the speaker 560, that is, the function of suppressing the dip indicated
by R2 in FIG. The length of the hollow region of the third resonator 590a is designed to be 1⁄4 of
the wavelength of the sound wave at the frequency at which the dip occurs.
[0051]
The fourth resonator 590b has a function of reducing the sound pressure of a specific frequency
excited by the vibration of the speaker 560, that is, the function of suppressing the dip indicated
by R2 in FIG. The length of the hollow region of the fourth resonator 590b is designed to be 1/4
the wavelength of the sound wave at the frequency at which the dip occurs.
[0052]
In the inner space 582 where each speaker 560 is installed, the position where the opening 591a
of the third resonator 590a is located is the position of the antinode of the sound pressure of the
natural vibration mode of the frequency at which dip occurs. The position where the opening
591b of the resonator 590b is located is the position of the antinode of the sound pressure of the
natural vibration mode of the frequency at which the dip is generated. The third resonator 590a
and the fourth resonator 590b resonate by the sound waves including the frequency at which
dips are generated from the openings 591a and 591b of the third resonator 590a and the fourth
resonator 590b entering the hollow region. In the vicinity of the openings 591a and 591b, the
sound pressure is reduced centering on the frequency, and the reaction force of the speaker 560
is released. This will be described with reference to FIG. FIG. 24A shows the sound pressure in
the natural vibration mode at the frequency at which dips occur when the resonator 590 is not
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24
disposed in the internal space 582, and FIG. 24B shows the resonance in the internal space 582.
The figure shows the sound pressure of the natural vibration mode at the frequency at which dip
occurs when the body 590 is disposed. As shown in FIG. 24A, when there is an antinode of sound
pressure of the natural vibration mode of the frequency fd at which the dip occurs, it is assumed
that a dip as shown by R2 in FIG. 16 occurs. Conceivable. When the resonator 590 is disposed in
the internal space 582 of such a speaker box 580, the resonator 590 resonates by positioning
the opening 591 at the antinode of the sound pressure of the natural vibration mode of the
frequency fd, and the resonance occurs. The sound pressure of fd is reduced, the reaction force
of the speaker 560 is released, and the dip of the frequency fd is suppressed. More specifically,
in FIG. 24B, for example, dips in FIG. 16 or FIG. 19A occur where the openings 591a and 591b of
the third resonator 590a and the fourth resonator 590b are placed in each speaker installation
space It is a place of the antinode of the natural vibration mode in the speaker box at the
frequency fd, and when the third resonator 590a and the fourth resonator 590b resonate at the
frequency fd, the sound wave of the natural vibration mode of the frequency fd The position is
such that the size Si decreases.
[0053]
Also, as shown in FIG. 24C, the positions where the openings 591a and 591b of the third
resonator 590a and the fourth resonator 590b are located in each speaker installation space are
the antinode locations of the sound pressure of the natural vibration mode of the frequency fd.
As the third resonator 590a and the fourth resonator 590b resonate at the frequency fd, the
node of the sound pressure of the natural vibration mode of the frequency fd is the center Ps of
the speakers 560a and 560b (speaker voice coil It is also possible to set the position so as to be
located near each axial position). Here, in the vicinity of the center Ps of the speaker 560 where
the node of the sound pressure is located, the region where the distance from the center Ps of the
speaker 560 is λ / 8 (λ is the wavelength of the sound wave of the natural vibration mode of
the frequency fd) is desirable. Thus, the reaction force of the speaker 560 is released also by
locating the node of the sound pressure in the area within λ / 8 from the center Ps of the
speaker 560. According to this, as shown in FIG. 24A, when antinodes of sound waves of the
natural vibration mode of the frequency fd are present at the center position Ps of the speaker
560, the openings 591a and 591b of the resonator 590 are natural vibration modes of the
frequency fd. Positions of the sound waves of the sound waves, and are arranged so that the
distance from the center Ps is less than λ / 8.
[0054]
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25
Furthermore, I will continue the explanation. FIG. 24A shows the state of a standing wave
generated in the speaker box when the third resonator 590a and the fourth resonator 590b are
not present in the speaker box. FIG. 24C shows a state where standing waves are present in the
speaker box as shown in FIG. 24A, the openings 591a and 591b of the third resonator 590a and
the fourth resonator 590b are at the center Ps of the speakers 560a and 560b. The natural
vibration mode (mode) of the standing wave is changed by placing it in the vicinity, and the
natural vibration mode of the standing wave is set so that the position of the center Ps of the
speakers 560a and 560b becomes the position of the node of the standing wave. It represents
the changed state. When the third resonator 590a and the fourth resonator 590b are placed at a
position where the standing wave is in such a natural vibration mode, the diaphragm of the
speaker 560 is easily vibrated, and the dip shown in FIG. 16 and FIG. 19A is The effect of
becoming smaller can occur. As shown in FIG. 24A, when there is an antinode of sound waves of
the natural vibration mode of frequency fd at the center position Ps of the speaker 560, the
positions of the third resonator 590a and the fourth resonator 590b and the centers Ps of the
speakers 560a and 560b It is desirable to arrange the opening 591 of the resonator 590 within
the range of λ / 8 from the center Ps of the speaker 560 because the above action is considered
to be practically possible if the deviation of the position of up to λ / 8. It is
[0055]
Further, as a modification of the present embodiment, it is also possible to dispose the resonator
590 at a position as shown in FIG. 25B. That is, as shown in FIG. 25A, the resonator 590 is the
position of the antinode of the sound pressure of the natural vibration mode at the frequency at
which dip occurs when the resonator 590 is not provided. By arranging the openings 591a and
591b of the third resonator 590a and the fourth resonator 590b at positions away from the
center Ps of 560b, as shown in FIG. 25B, the characteristic frequency of the dip is generated. The
magnitude Si of the sound wave in the vibration mode can be reduced to suppress the occurrence
of dip. Further, as shown in FIG. 25C, the openings 591a and 591b are located at the antinode
position of the sound pressure of the natural vibration of the frequency at which the dip is
generated, away from the center Ps of the speakers 560a and 560b. By arranging, as shown in
FIG. 25C, the node of the natural vibration mode of the frequency at which the dip is generated
may be positioned near the center Ps of the speakers 560a and 560b to suppress the occurrence
of the dip.
[0056]
<Modified example> Hereinafter, the modified example of embodiment mentioned above is
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26
demonstrated. (1) Although the example which installs four resonators 32 in the internal space of
the housing | casing part 3 which concerns on Embodiment 1 mentioned above was
demonstrated, you may comprise as follows. FIG. 26 is a simplified view of the internal space of
the housing 3 as viewed from above. As shown in FIG. 26 (a), the resonator 32 is not provided,
and the partition plate 70 is provided between the speaker 30a and the speaker 30b so that the
position of the speakers 30a and 30b becomes a node of sound pressure of the natural vibration
mode in the internal space. May be provided. Further, as shown in FIG. 26 (b), the partition plate
70 is provided in the same manner as FIG. 26 (a), and each space partitioned by the partition
plate 70 is an antinode of sound pressure of the natural vibration style in the space. The
resonator 32a may be arranged so that the opening 321 of the resonator 32a is located at a
location.
[0057]
(2) The arrangement of the first resonator 80a and the second resonator 80b provided in the
internal space of the housing 3A according to the second embodiment described above is not
limited to the aspect described in the second embodiment, and the following aspects It may be
FIG. 27 is a simplified view of the lower internal space of the housing 3A according to the
present modification as viewed from the front. In FIG. 27 (a), the partition plate 70 is not
provided, and each pair of two first resonators 80a and two second resonators 80b is provided at
predetermined positions of the speaker 60a and the speaker 60b at upper and lower portions. It
is. The opening 801 a of the first resonator 80 a and the opening 801 b of the second resonator
80 b provided on the side of the speaker 60 a are directed in the arrow L direction. Further, the
opening 801 a of the first resonator 80 a and the opening 801 b of the second resonator 80 b
provided on the side of the speaker 60 b are directed in the arrow R direction. As in the second
embodiment, the position of the opening 801a of each first resonator 80a is the location of the
antinode of the sound pressure of the natural vibration mode of the frequency being excited, and
the opening of each second resonator 80b The position 801 b is on the boundary surface which
is separated from the center of gravity of each of the speakers 60 a 60 b by a distance of 1⁄4 of
the wavelength of the frequency that generates the reaction force that suppresses the vibration
of the speakers 60 a 60 b.
[0058]
Further, in the arrangement of the first resonator 80a and the second resonator 80b shown in
FIG. 27 (a), partition plates may be provided as shown in FIG. 27 (b) or (c). In the case of FIG. 27
(b), only one partition plate 70 is provided. In this case, for example, the partition plate 70 may
16-04-2019
27
be provided such that the position of the speaker 60a is a node of the sound pressure of the
natural vibration mode. In other words, by providing the partition plate 70 so that the position of
at least one speaker is a node of the sound pressure of the natural vibration mode, the number of
natural vibration modes excited by the vibration of the speaker may be reduced.
[0059]
Further, as shown in FIG. 27 (d), resonators 80c and 80d may be provided between the partition
plates 70a and 70b in the arrangement shown in FIG. 27 (c). The resonators 80c and 80d have
an opening and a hollow region, like the first resonator 80a and the second resonator 80b. The
opening of the resonator 80c is disposed downward, and the opening of the resonator 80d is
disposed upward. The resonator 80c may resonate at the same frequency as the second
resonator 80b, and the resonator 80d may resonate at the same frequency as the first resonator
80a. In addition, the resonator 80c and the resonator 80d may resonate at another frequency.
[0060]
(3) The housing portion of the electronic keyboard instrument according to the embodiment
described above may be shaped as shown in FIG. As in the first embodiment, such as a
rectangular parallelepiped as in the case 3B shown in FIG. 28 (a), or a polygon such as in the case
3C as shown in FIG. 28 (b). The shape of the housing may be such that a one-dimensional natural
vibration mode occurs in the arrangement direction of the keys in the internal space of the
housing portion. In this case, the speaker 30 may be disposed such that the sound emitting
surface of the speaker 30 faces in the bottom surface direction or the top surface direction of the
housing portion. Further, it may be a rectangular parallelepiped shape as in the case 3D shown in
FIG. 28 (c). That is, as in the second embodiment, any shape other than the second embodiment
may be used as long as a two-dimensional natural vibration appearance occurs in the height
direction and the arrangement direction of the keys. In this case, the sound emitting surface of
the speaker 60 may be arranged to face the player or the back side.
[0061]
(4) In each embodiment described above, an example using a tube-shaped resonator has been
described, but various resonators such as plate vibration resonance, Helmholtz resonance,
bending plate vibration, piston plate vibration and the like may be used. The point is that the
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resonator is a resonator designed in consideration of the coupling with the sound field in the
internal space of the housing part of the electronic keyboard instrument, and controls the
acoustic energy in the internal space of the housing part. I hope there is. Specific examples of the
resonator are shown below.
[0062]
FIG. 29A is a view schematically showing the appearance of the plate vibration resonator. FIG. 29
(b) is a cross-sectional view of the plate vibration resonator 110 as viewed from the arrow VI-VI
in FIG. 29 (a). The plate vibration resonator 110 includes a housing portion 110A and a vibrating
portion 110B. The housing portion 110A is a box-shaped member having a rectangular
parallelepiped shape in which the entire upper surface side is open. The housing portion 110A
has an opening 110C and a rectangular parallelepiped gas layer 110D as a hollow area
communicating with the opening 110C. The housing 110A is made of, for example, wood, but
other materials such as synthetic resin or metal may be used as long as the material is relatively
harder than the vibrating portion 110B. The vibrating portion 110 </ b> B is elastic and is a
plate-like or film-like rectangular member. The vibrating portion 110D may be formed, for
example, of an elastic material such as a synthetic resin, a metal, a fiber plate, or a closed cell
foam formed into a plate, or an elastic material or a polymer compound. What was formed into is
used. The region near the end of one surface of the vibrating portion 110B is supported by the
housing 110A, and is provided so as to close the opening 110C of the housing 110A. By closing
the opening 110C with the vibrating portion 110D, a closed gas layer 110D is formed inside the
plate vibration resonator 110. The gas layer 110D is a layer made of gas particles, and in this
example is an air layer made of air molecules, but an elastic body such as a porous material may
be provided in the gas layer 110D. The plate vibration resonator 110 is provided such that the
vibrating portion 110B is located at the antinode position of the sound pressure of the sound
wave of the target frequency. When a sound is generated in the space, the plate vibration
resonator 110 resonates in accordance with the sound pressure of the sound. This resonance
causes a difference between the sound pressure in space and the pressure in the gas layer 110D
of the plate vibration resonator 110. The pressure difference causes the vibrating portion 110B
to vibrate, and after the acoustic energy is consumed, the acoustic energy is re-radiated. By this
action, the sound pressure is reduced in the space near the surface of the vibrating portion 110B,
which is the surface of the plate vibration resonator 110.
[0063]
FIG. 30 (a) is a view schematically showing the appearance of the Helmholtz resonator, and FIG.
16-04-2019
29
30 (b) is a cross-sectional view of the Helmholtz resonator 120 viewed from the arrow VIII-VIII in
FIG. 30 (a). FIG. The Helmholtz resonator 120 is composed of a body 120A and a tube 120B. In
the Helmholtz resonator 120, a space formed in the trunk portion 120A and the tube portion
120B is a hollow area, and the hollow area communicates with the opening 120C. The body
portion 120A has a gas layer formed therein, and is cylindrically formed of, for example, FRP
(fiber-reinforced plastic). The pipe portion 120B is a so-called open-ended tubular member made
of, for example, vinyl chloride, and is inserted into the hole portion of the body portion 120A and
the both are connected. The Helmholtz resonator 120 is provided so that the opening 120C is
located at the antinode position of the sound pressure of the sound wave of the target frequency.
As a result, sound enters the opening 120C, the Helmholtz resonator 120 resonates, and the
sound pressure near the opening 120C is reduced. That is, the Helmholtz resonator 120 forms a
spring mass system in which the gas inside the tube portion 120B is a mass component and the
gas layer of the trunk portion 120A is a spring component. The friction between the inner wall of
the tube portion 120B and the air converts the energy of the sound into heat energy, which
reduces the sound pressure near the opening 120C and increases the particle velocity. The
resonance frequency f of the spring-mass system of the Helmholtz resonator 120 satisfies the
relationship of Formula (2). However, in Formula (2), Le represents the effective length of the
pipe part 120B. As shown in FIG. 30B, the effective length Le is a length obtained by correcting
the length from one end to the other end of the cavity of the tube portion 120B with the opening
end correction value. Also, V is the volume (that is, the volume) of the gas layer formed in the
trunk portion 120A, and So is the area of the opening 33. f = c0 / 2π (So / Le · V) <1/2> (2) In
addition, although the number of tube portions 120B is one here, a plurality of tube portions
120B may be provided. Moreover, it may be closed by the flow resistance material which has air
permeability, such as glass wool, cloth, gauze, etc. in the opening part 120C of the tube part
120B or its vicinity, and has a flow resistance.
[0064]
FIG. 31 is a view showing a resonator according to the present modification. FIG. 31 (a) is a view
showing the appearance of the resonator of this modification. The appearance of the resonator
130 is open at one end (left side in the drawing) and forms a closed tubular shape at the other
end (right side in the drawing). The configuration of the resonator 130 is roughly divided into a
tubular member 130A and a resistive material 130B. The tubular member 130A is an example of
the housing of the present invention, and is formed in a cylindrical shape using, for example,
metal or plastic as a material. The tubular member 130A is a so-called one-end tubular member
and extends in one direction here. The resistance member 130B is a member having a shape in
which a cylindrical cavity is opened so as to penetrate the vicinity of the center of both bottom
surfaces of the cylinder. The resistance material 130B is provided near the opening end of the
tubular member 130A such that a surface corresponding to the outer circumferential surface of
16-04-2019
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the cylinder is in contact with the inner surface of the tubular member 130A. The resistance
member 130B is formed using urethane foam, which is an example of a porous material, as a
material, and is a member that resists the movement of gas particles (here, air molecules) to
inhibit the movement of the gas particles. It is. The region where the resistive material 130B is
disposed has an increased resistance to the movement of gas particles as compared to when the
resistive material 130B is not disposed. Also, as a physical quantity that quantitatively represents
the resistance value of this resistance, there is a characteristic impedance of the medium.
[0065]
31 (b) is a view showing a cross section when the resonator 130 is cut along a cutting line II-II in
FIG. 31 (a). That is, FIG. 31 (b) is a cross-sectional view of the case where the acoustic resonator
10 is cut along a plane including the x-axis described later along the extending direction of the
tubular member 130A. 31 (c) and 31 (d) are views showing cross sections of the resonator 130
cut along a plane orthogonal to the extending direction of the tubular member 130A. When each
position where the resistive material 130B is provided is cut in the extending direction of the
resonator 130, the cross-sectional shape of the tubular member 130A is the same shape and the
same size. Moreover, the cross-sectional shape of the resistance material 130B is also the same
shape and the same dimension, respectively. The tubular member 130A has a circular open end
131 at one end and the same circular closed end 132 at the other end. The closed end 132 is
acoustically considered to behave the same as a fully reflective surface (ie, a rigid wall). Inside the
tubular member 130A, a cylindrical hollow region 130C extending between the open end 131
and the closed end 132 is formed. The hollow region 130C communicates with the external
space through the open end 131. Here, a length between both ends of the hollow region 130C,
which is a distance between the open end 131 and the closed end 132, is L. Then, a line
connecting the centers of the cross sections orthogonal to the extending direction of the hollow
region 130C is indicated by “central axis x” (indicated by an alternate long and short dash
line). It defines as). The diameter of the open end 131 of the tubular member 130A is sufficiently
smaller than the wavelength of the resonant frequency of the resonator 130 (for example, 1/2 or
less). Thereby, in the case of the tubular member 130A alone, the sound wave traveling to the
hollow region 130C can be regarded as only a plane wave traveling in the direction along the
central axis x. Therefore, in the hollow area 130C, the sound pressure is substantially uniformly
distributed in the same area in the direction along the central axis x, that is, in the area included
in the cross section orthogonal to the central axis x. The resistance member 130B is provided in
the hollow region 130C with the position of the open end 131 as one end. Here, the resistive
material 130B has a longitudinal direction along the central axis x direction. The length of the
resistive material 130 B with respect to the longitudinal direction is set, and the distance from
one end to the other end located at the opening end 131 is defined as 10. Since the resistive
material 130B has a cavity penetrating in a direction corresponding to the longitudinal direction
16-04-2019
31
of the cylinder, the open end 131 and the closed end 132 of the tubular member 130A
communicate with each other through the cavity.
This cavity is here an area without members that increase the resistance to the movement of the
gas particles. The resonance frequency of the resonator 130 shifts to the lower frequency side as
the length l0 of the resistive material 130B increases, that is, as the length L-l0 of the hollow
region 130C decreases.
[0066]
(5) In addition, in the resonator, an adjustment mechanism may be provided to adjust the
resonance frequency of the resonator. The adjustment mechanism is used even in the case of
reducing the sound pressure of the natural vibration style of a plurality of different frequencies
by using a resonance body provided with an adjustment mechanism for adjusting a resonance
frequency as a resonance body provided in a housing of an electronic keyboard instrument. Since
it is sufficient to adjust the resonance frequency by the above, it is possible to use a resonator
having a common shape and size. Hereinafter, an example of such an adjustment mechanism will
be described.
[0067]
(A) For example, in the case of a tubular resonator as in the first and second embodiments
described above, a porous material such as urethane foam is used as an example of an
adjustment mechanism for adjusting the length of the hollow region of the resonator. The hollow
region is formed by adhering a member which is formed using the material and which resists the
movement of the gas particle (here, air molecule) to inhibit the movement of the gas particle to
the closed portion of the hollow region of the resonator. The length may be changed. As the
length of the hollow region is increased, the resonance frequency is shifted to the lower
frequency side.
[0068]
(B) Further, as an example of the adjustment mechanism, for example, as shown in FIG. 32A, in
the cylindrical resonance body 200 similar to that of the second embodiment, the position of the
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32
opening 210 is adjusted to adjust the hollow area 211. A cylindrical member 212 for adjusting
the length may be provided. In this case, the member 212 has the same outer peripheral
diameter as the inner peripheral diameter of the hollow region 211, and a hole having the same
size as the outer periphery of the member 212 is provided on the surface of the resonator 200
into which the member 212 is inserted. ing. Further, a screw thread and a screw groove are
respectively provided on the inner periphery of the hollow region 211 and the outer periphery of
the cylindrical member 212, and the member 212 is fitted to the hollow region 211 by fastening
the screw thread and the screw groove. By rotating the member 212 with respect to the
resonator 200, the length L of the hollow area is adjusted. As the length L of the hollow region
211 becomes longer, the resonance frequency is shifted to the lower frequency side.
[0069]
(C) Further, as an example of the adjustment mechanism, as shown in FIG. 32 (b1), for example,
as in the second embodiment, the cylindrical resonator 310 having one end opened and the other
end closed is flexible. The material has a bellows-shaped side surface 311, and by moving the
closing portion 312 upward, the length L of the hollow region 313 is increased as shown in FIG.
33 (b2). As the length L of the hollow region 313 becomes longer, the resonance frequency is
shifted to the lower frequency side.
[0070]
(D) In addition, as an example of the adjustment mechanism, for example, the length of the
hollow region in the tube portion in which the closed surface side of the resonator according to
the first embodiment is opened and the outer peripheral surface on the closed surface side is
provided with a screw thread The adjustment may be performed by a lid member that has a
thread groove that engages with the thread, and that closes the surface on the closing portion
side. FIG. 32 (c1) is a view showing a cross section of the above-mentioned tube portion 320A.
The tube portion 320A has a hollow region of a length L, and has an opening 321 and an
opening 323A on the closing portion side. A screw thread is provided by a predetermined length
on the outer peripheral surface on the closed port side of the pipe portion 320A. 32 (c2) and 32
(c3) are diagrams showing an example of the lid member. As shown in FIGS. 32 (c2) and (c3), the
lid members 320B and 320C are provided with screw grooves to be fitted with the screw threads
of the tube portion 320A, and the diameter d of the hollow region of the tube portion 320A (tube
portion A protrusion 324 having a diameter slightly smaller than the distance from the axial
center of 320A to the inner periphery of the tube 320A × 2) is provided. The lengths of the lids
320B and the protrusions 324 of the lids 320C are different from l1 and l2 (l1> l2). By fitting the
16-04-2019
33
protrusions 324 of the lid members 320B and 320C into the opening 323A on the closing part
side of the pipe part 320A, the closing part side of the pipe part 320A is closed to form a closing
part. For example, when the lid member 320B is fitted into the pipe portion 320A by the length
I1 of the projection 324, the length of the hollow region of the pipe portion 320A is (L-11).
When the lid member 320C is fitted in the pipe portion 320A by the length 12 of the projection
324, the length of the hollow region of the pipe portion 320A is (L-l2), and the lid member 320B
is used as the pipe portion 320A. The hollow area is longer than in the case of fitting. Thus, the
resonant frequency of the resonator can be adjusted by adjusting the length of the hollow region
of the tube portion 320A with a plurality of lid members having different lengths of the
protrusion 324. In addition, the length of the hollow region of the tube 320A may be adjusted by
changing the length of fitting the protrusion of each lid member into the tube 320A. Further, in
the state where lid members 320B and 320C shown in FIGS. 32 (c2) and (c3) are respectively
fitted in the tube portion 320A by the length of the protrusion 324, the length in the longitudinal
direction of the resonator is apparently Same length. Therefore, it is possible to reduce the
useless space when arranging the resonator, the electronic component, and the like in the
internal space of the housing 3.
[0071]
(E) In the modification of (a) to (d) described above, an example in which the resonance
frequency of the resonator is adjusted by adjusting the length of the hollow region of the tubular
resonator has been described. The volume of the hollow region may be adjusted to adjust the
resonance frequency without changing the length of the hollow region of the body. FIG. 32 (d 1)
is a view showing a cross section of a resonator according to the present modification. As shown
in FIG. 32 (d1), the resonator 330 is formed in a tubular shape having a hollow area P1 which is
open at one end and closed at the other end. An opening 331 having a diameter d1 is provided in
part of the side surface of the resonator 330, and in this figure, the opening 331 is closed by the
member 331A. The member 331A for closing the opening 331 is configured to be removable,
and when adjusting the resonance frequency of the resonator 330, as shown in FIG. 32 (d2),
instead of the member 331A, the outer peripheral surface is A tubular member 332 provided
with a screw thread and open at both ends is adhered to the end of the opening 331, and has a
shape similar to the shape shown in FIGS. 32 (c2) and (c3) And a lid member 333 having a
thread groove to be engaged with the tubular member 332. In a state where the lid member 333
is connected to the tubular member 332, a space P2 from the opening 331 connected to the
hollow region P1 to the projection of the lid member 333 is formed, and the volume of the
hollow region of the resonator 330 is increased. As the volume of the hollow region of the
resonator 330 increases, the resonance frequency of the resonator 330 is shifted to the lower
frequency side. As a preferred example of using the above-described resonator shown in FIG. 32,
cases in which the same resonator is used in a plurality of models having different housing
16-04-2019
34
structures, or in which the acoustic characteristics change due to the arrangement or addition of
internal parts due to a change in product design Can be easily coped with.
[0072]
(F) Next, an example of a Helmholtz resonator provided with an adjustment mechanism is shown
in FIG. The Helmholtz resonator 410 shown in FIG. 33 (a) is configured by a trunk portion 410A
and a tube portion 410B, as with the Helmholtz resonator 120 described above. The trunk
portion 410A has a bowl shape having a neck portion 411, and the neck portion 411 has a pipe
having an outer peripheral diameter equal to the inner peripheral diameter of the pipe portion
410B. A screw thread and a screw groove are respectively provided on the inner periphery of the
tube portion 410B and the outer periphery of the neck portion 411, and the pipe portion 410B
and the tube portion 410B of the trunk portion 410A are fitted by fastening the screw thread
and the screw groove. Ru. By rotating the body portion 410A with respect to the pipe portion
410B, the pipe length L including the neck portion 411 and the pipe portion 410B is adjusted.
The resonance frequency of the Helmholtz resonator 410 is shifted to the lower frequency side
as the tube length L becomes longer. The side surface of the tube portion 120B of the Helmholtz
resonator 120 is formed into a bellows like a flexible material as described in (c) above, and the
tube portion 120B is changed by moving the body portion 120A to change the length of the tube
portion 120B. The length of the hollow region of 120 B may be adjusted.
[0073]
In the Helmholtz resonator 410 shown in FIG. 33 (a), the resonance frequency is adjusted by
adjusting the tube length L. However, the resonance frequency may be adjusted by adjusting the
volume of the trunk portion 410A. Good. FIG. 33 (b) shows an example of a Helmholtz resonator
420 having an adjustment mechanism for adjusting the volume of the body. The Helmholtz
resonator 420 includes a body 420A having a hollow area 422, and an opening 421 in contact
with the external space, and a pipe 420B having a conduit 423 communicating from the opening
421 to the hollow area 422 of the body 420. There is. A screw thread is provided on the inner
peripheral surface of the body 420A, and a cylindrical member 420C is inserted into a hole
provided on the bottom of the body 420A. The member 420C has an outer peripheral diameter
the same as the inner peripheral diameter of the body 420A, and on the outer periphery, a thread
groove to be fitted to the screw thread is provided. By rotating the member 420C with respect to
the body 420A and moving the member 420C in a direction in which the member 420C is moved
toward and away from the body 420A, the volume of the hollow region 422 of the body 420A is
increased. As the volume of the hollow region 422 of the body 420A increases, the resonance
16-04-2019
35
frequency is shifted to the lower frequency side. As shown in FIGS. 33A and 33B, the Helmholtz
resonator may be provided with any one of an adjusting mechanism for adjusting the tube length
and an adjusting mechanism for adjusting the volume of the hollow region of the trunk. And both
adjustment mechanisms may be provided.
[0074]
Further, an adjustment mechanism may be provided to adjust the inner diameter of the tube
portion 120B of the Helmholtz resonator 120 described above. As an adjustment mechanism, for
example, a cylindrical member having the same outer peripheral diameter as the diameter of the
hollow region of the tube portion 120B, the same length as the length of the hollow region of the
tube portion 120B, and having both ends opened The tube 120B is attached to the portion 120B
to reduce the diameter of the tube 120B. The resonance frequency shifts to the lower frequency
side as the inner diameter of the tube portion 120B becomes smaller. Further, as an adjusting
mechanism for adjusting the resonance frequency of a plate vibration resonance body, a bending
plate vibration resonance body, etc., a material having elasticity and producing elastic vibration
such as synthetic resin, metal, fiber plate, closed cell foam body is plate-shaped An additional
material such as a weight may be provided on the diaphragm formed in the above. The additional
member may be attached to a region including a position where the amplitude is maximized
when the diaphragm is bent and vibrated. As the mass of the diaphragm increases, the resonance
frequency of the bending system shifts to the low frequency side.
[0075]
(6) In the second embodiment described above, an example in which the partition plate 70 is
provided has been described, but by arranging an electric component such as a circuit board at
the position of the partition plate 70, the electric component can be used as a partition plate
Good. In the second embodiment, although the example in which the resonator 80 is attached to
the inner wall of the back plate 55 has been described, other members (the inner wall of the
front plate 49, the shelf plate 53) provided in the internal space of the housing 3A. And the like
may be integrally formed. For example, as shown in FIG. 34, a partition / resonance member in
which a resonator and a partition plate are integrally formed may be used. FIG. 34 (a) is a
simplified view showing a speaker installation space. As shown in FIG. 34 (b), in the installed
state, the partition / resonance member 700 has a bottom surface 710a shorter than a surface
711 located on the side of the speakers 60a and 60b and a surface 711 facing the surface 712. It
has a rectangular parallelepiped shape that is open and closed at the upper portion 710b, and a
hollow region 713 is provided inside. For example, in the case where the partition and resonance
16-04-2019
36
member 700 functions as a second resonator, the surface 712 is such that the length L of the
hollow region 713 is 1⁄4 of the wavelength of the frequency to be reduced in sound pressure.
Design the length of the
[0076]
(7) As the electronic keyboard instrument according to the first embodiment described above, a
table-top type electronic piano as shown in FIG. 35 may be applied. In this figure, a keyboard 11
is provided in a housing portion 3E of the electronic keyboard instrument 1, and a TE 17a is
provided in the upper part of the keyboard 11. The speaker 30 is provided in the internal space
of the housing 3E so that the sound emitting surface is in the upper surface direction, and the
resonator 32 is provided in the space below the speaker 30. The space in which the speaker 30
is provided and the space in which the keyboard 11 is provided are connected in the internal
space of the housing 3E, and the housing 3E is configured to transmit the sound from the
speaker 30 to the external space from the sound emitting surface. To transmit the sound of the
speaker 30 to the external space from the gap between the keys of the TE 17a and the keyboard
11 via the first sound emission path to be transmitted and the space behind the speaker 30, that
is, the space under the speaker 30. And 2 sound emission paths. As in the first embodiment, the
position of the opening of the resonator 32 is the position of the antinode of the sound pressure
of the natural vibration mode of the frequency for which the sound pressure is to be reduced in
the space where the speaker 30 is provided. As the second sound emission path, there is a sound
emission path through which sound is transmitted toward the side or the back side of the
keyboard 11 from the gap of the part where the upper case and the lower case of the electronic
keyboard instrument are combined. It may be done.
[0077]
(8) As described above, the tubular resonator according to the embodiment and the modification
is a pipe having a uniform cross section perpendicular to the longitudinal direction at any
position extending in the longitudinal direction, and one end thereof It can be said that it is an
acoustic damper body which consists of a tube material which made the shielding end which
shields acoustically. The Helmholtz resonance body according to the embodiment and the
modification described above is a container having a hollow portion, and one end of the hollow
portion is opened and a portion recessed from the one end to the other end is the one described
above. It can be said that it is an acoustic damper body provided with a cave part which has an
area larger than the end opening area. Further, the Helmholtz type resonator in a narrow sense is
an acoustic system in which a cave having a predetermined length in the depth direction from
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one end has a uniform cross section while a further back has a cave having a larger cross section
than the cross section. It can be said that it is a damper body. In short, the resonator according to
the embodiment and the modification described above is defined as an acoustic damper having
an opening at one end and a cavity in a direction in which the cavity is recessed from the one
end.
[0078]
(9) In the embodiment and the modification described above, an example in which the TE is
provided in the electronic keyboard instrument has been described, but an electronic keyboard
instrument in which the TE is not provided may be used. In short, it has a second sound emission
path for propagating the sound of the speaker to the external space from a path that leads
acoustically to the outside of the housing such as a key gap of the keyboard via the internal
space of the housing in which the speaker is provided. It may be an electronic keyboard
instrument. Further, the second sound emission path for propagating the sound of the speaker to
the external space via the internal space of the housing provided with the speaker is not limited
to the gap of the key of TE or the keyboard. For example, an electronic guitar having an internal
speaker with a path leading the sound on the back of the sound emitting surface to the outside,
an electronic stringed instrument such as an electronic violin, a speaker is provided, and the
sound on the back of the sound emitting surface is led to the outside The present invention may
be applied to an electric stringed instrument such as an electric guitar having a path, and an
electronic percussion instrument such as a percussion or the like having a path for guiding the
sound on the back of the sound emitting surface to the outside.
[0079]
(10) In the second embodiment and the second modification described above, an example in
which one speaker is provided in each of the spaces partitioned in the lower inner space S2 of
the housing 3A has been described. As shown to (a), several speaker 60a and 60b may each be
provided in partitioned space S21, S21. Further, as shown in FIG. 36 (b), the speaker 60c may be
provided in the space where the resonator 80 is not provided in the lower internal space S2. Also,
as shown in FIG. 36 (c), in the lower internal space S2, two speakers 60a are provided in one
space S22 provided with the resonator 80, and three speakers 60b are provided in the other
space S23. May be provided. The point is that the internal space is partitioned so as to divide two
or more speakers into at least two or more, and the resonators 80 are provided in any two or
more of the partitioned spaces in which the speakers are located Good. In the above-described
embodiment, an example in which two speakers are provided in the housing unit has been
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38
described. However, the number of speakers is not limited to this and may be more or less. That
is, at least one speaker may be provided in the housing portion.
[0080]
(11) In the second embodiment described above, an example of the electronic keyboard
instrument has been described, but it is applicable to any sound system having a speaker having
a sound emission path for guiding the vibration from the back of the sound emission surface of
the speaker to the outside. . For example, the present invention may be applied to a speaker box
mounted in a car. Specifically, the housing structure has a complicated shape, and the sound
generated in the housing is provided with a first resonator for reducing the sound pressure in the
natural vibration mode of at least one specific frequency, and the specific What is necessary is to
provide a resonator that reduces the reaction force to the movement of the speaker that occurs
at a frequency different from the frequency.
[0081]
1, 1A, 501A: electronic keyboard instrument, 2, 2A, 502A: keyboard unit, 3, 3A, 3B, 3C, 3D, 3E,
503A: case part, 4, 4A, 504A. · Pedal unit, 11, 41, 541 · · · keyboard, 11a · · · front panel, 12 · · ·
operation panel, 13, 43, 43 · · · arm portion, 14, 44, 44 · · · mouth piece, 15 , 45, 545 · · ·
keyboard lid, 16 · · · score board, 17 · · roof plate, 17a, 49a, 581a · · · · tone escape (acoustic
escape / TE), 18, 48, 548 · · · Side plate 19, 53, 553: Shelf plate, 20, 55: Back plate, 21: Bottom
member, 22: Wife base 30, 30, 30a, 30b, 60, 60a, 60b, ... Speakers 32, 32a, 32b ... Resonators
34, 90 ... Plate, 42, 542 ... beatwood, 46 ... music score holder, 50, 550 ... front leg, 51a, 51b,
551a, 551b ... saran net, 61 ... baffle plate, 70, 70a, 70b, 570 ... Partition plate, 80, 130, 200, 310
... Resonator, 80a ... First resonator, 80b ... Second resonator, 110 ... Plate vibration resonator,
120, 410 ... · · Helmholtz resonator, 549 · · · Front plate, 580 · · · Speaker box, 581 · · · 582 and
582 · · · Internal space, 700 · · · · · · · · · · · · · · 1 sound emission path first .. Second sound emission
path
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39
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