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JP2015215458

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2015215458
The present invention provides a pickup microphone system, a preamplifier unit, and a stringed
instrument that faithfully reproduce the original musical tones emitted by the stringed
instrument. A pickup microphone system includes a bi-directional microphone 42 disposed inside
the body 12 of the stringed instrument 10 and collecting musical tones resonating inside the
body 12. The bi-directional microphone 42 has a sound hole. A pointing axis L is along the
direction parallel to the plane where the 36 is open and perpendicular to the direction in which
the sound hole 36 is formed. As a result, it becomes possible to collect musical tones resonating
in the internal space of the body 12 without causing howling, and the original musical tones
emitted by the stringed instrument 10 can be faithfully reproduced. [Selected figure] Figure 5
Stringed instrument
[0001]
The present invention relates to a pickup microphone system, a preamplifier unit, and a stringed
instrument capable of faithfully reproducing the original musical tone emitted by the stringed
instrument.
[0002]
In general, stringed instruments such as ukulele and acoustic guitar transmit vibration to the
surface plate which is a resonance plate through the piece based on the vibration of the string,
and further resonate with a resonance shell having a sound hole to give a rich tone. .
04-05-2019
1
Therefore, different tones are produced for each individual instrument depending on the material
of the instrument such as the strings and the front plate, and the shape and structure of the
resonance cylinder. However, the volume of these instruments that do not have an electrical
amplification device can not be said to be sufficient, and when performing live performance in a
large venue such as a concert hall, the sound is collected using a microphone and amplified.
Increasing the volume has been done. However, if you pick up the sound of a stringed instrument
with a microphone, the sound of other instruments may be picked up and howling may occur.
Also, if the position of the microphone is fixed on the stage, it may not be possible to catch the
musical tone of the stringed instrument when the performer plays while moving around on the
stage.
[0003]
On the other hand, there is a method to increase the volume by attaching a piezo pickup
(piezoelectric pickup) to a resonance plate that constitutes a body (resonance body) of a stringed
instrument, converting string vibration to an electrical signal by the piezo pickup, and amplifying
this electrical signal. Are known. However, in the method using the piezo pickup, there is a
problem that the resonance sound called a box sound can not be sufficiently picked up and the
output sound becomes a thin and inorganic sound.
[0004]
To solve this problem, techniques have been proposed to add various effects to electrical signals
obtained using a piezo pickup, in order to be able to reproduce the resonance sound from the
body of a stringed instrument (for example, Patent Documents 1 to 3) reference).
[0005]
JP 2003-15644 JP JP 2005-24997 JP JP 2009-162997 JP
[0006]
However, although the techniques disclosed in Patent Documents 1 to 3 can process the
vibration of the string detected by the piezo pickup to a natural sound to some extent, the
resonance sound of the trunk can not be faithfully reproduced.
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Also, in order to detect the vibration of a string using a piezo pickup, the piezo pickup must be
attached to the most important part of the stringed instrument, which may adversely affect the
original timbre of the instrument.
[0007]
The present invention has been made in view of such circumstances, and it is an object of the
present invention to provide a pickup microphone system, a preamplifier unit, and a stringed
instrument capable of faithfully reproducing original musical tones emitted by the stringed
instrument.
[0008]
In order to achieve the above object, a pickup microphone system according to a first aspect of
the present invention comprises a hollow body, a sound hole formed in the body, a neck having
one end attached to the body, and a neck A pick-up microphone system for use in a stringed
instrument comprising a head attached to the other end of the head and a string stretched
between the head and the body, the tone being disposed inside the body and resonating inside
the body The bi-directional microphone has a pointing axis along a direction parallel to the plane
in which the sound hole opens and perpendicular to the direction in which the sound hole is
formed.
[0009]
The pickup system according to the second aspect of the present invention further includes, in
the first aspect, frequency correction means for flattening frequency characteristics of a signal
output from the bidirectional microphone.
[0010]
In a first aspect or a second aspect of the present invention, in a first aspect or a second aspect of
the present invention, there is provided a notch filter for attenuating a frequency component
centered on a notch frequency with respect to an input signal; It further comprises howling
suppression means including a howling detection means for detecting and a control means for
setting the howling frequency detected by the howling detection means to the notch frequency of
the notch filter.
[0011]
A preamplifier unit according to a fourth aspect of the present invention comprises a hollow
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body, a sound hole formed in the body, a neck having one end attached to the body, and a head
attached to the other end of the neck A pickup microphone system for use in a stringed
instrument comprising a string stretched between a head and a body, the bi-directional
microphone being disposed inside the body and collecting tones resonating inside the body. The
bi-directional microphone is a preamplifier unit for a pickup microphone system having a
pointing axis along a direction parallel to a plane in which the sound hole is opened and
perpendicular to a direction in which the sound hole is formed, A frequency correction unit is
provided to flatten the frequency characteristics of the signal output from the bidirectional
microphone.
[0012]
A preamplifier unit according to a fifth aspect of the present invention comprises a hollow body,
a sound hole formed in the body, a neck having one end attached to the body, and a head
attached to the other end of the neck A pickup microphone system for use in a stringed
instrument comprising a string stretched between a head and a body, the bi-directional
microphone being disposed inside the body and collecting tones resonating inside the body. The
bi-directional microphone is a preamplifier unit for a pickup microphone system having a
pointing axis along a direction parallel to a plane in which the sound hole is opened and
perpendicular to a direction in which the sound hole is formed, A notch filter that attenuates
frequency components centered on the notch frequency with respect to the input signal, and a
howling frequency included in the input signal Comprising a howling detection means for
detecting, the howling suppressing means and a control means for setting the detected howling
frequency feedback detector to the notch frequency of the notch filter.
[0013]
A preamplifier unit according to a sixth aspect of the present invention comprises a hollow body,
a sound hole formed in the body, a neck having one end attached to the body, and a head
attached to the other end of the neck A pickup microphone system for use in a stringed
instrument comprising a string stretched between a head and a body, the bi-directional
microphone being disposed inside the body and collecting tones resonating inside the body. The
bi-directional microphone is a preamplifier unit for a pickup microphone system having a
pointing axis along a direction parallel to a plane in which the sound hole is opened and
perpendicular to a direction in which the sound hole is formed, Frequency correction means for
flattening the frequency characteristics of the signal output from the bi-directional microphone,
and centering on the notch frequency with respect to the input signal Howling suppression
means including a notch filter for attenuating the wavenumber component, a howling detection
means for detecting the howling frequency contained in the input signal, and a control means for
setting the howling frequency detected by the howling detection means to the notch frequency of
the notch filter And.
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[0014]
A stringed instrument according to a seventh aspect of the present invention comprises a hollow
body, a sound hole formed in the body, a neck having one end attached to the body, and a head
attached to the other end of the neck. A stringed instrument comprising a string suspended
between a head and a body, and a pickup microphone system according to any one of the first to
third aspects.
[0015]
According to the present invention, since the direction in which the sensitivity of the bidirectional microphone is minimum is directed to the sound hole, it becomes possible to collect
musical tones resonating in the internal space of the body without causing howling. The original
musical tones emitted by the stringed instrument can be faithfully reproduced.
[0016]
FIG. 1 is a plan view of the stringed instrument shown in FIG. 1; FIG. 3 is a perspective view of
the microphone unit shown in FIG. 3; FIG. 3 is an exploded perspective view of the microphone
unit; A diagram showing the characteristics A block diagram showing the configuration of the
preamp unit A diagram showing the frequency characteristics of the output signal of the bidirectional microphone A diagram showing the frequency characteristics of the gradient filter A
diagram showing the frequency characteristics of the notch filter External view showing an
example A side view of the stringed instrument shown in FIG.
[0017]
Hereinafter, preferred embodiments of the present invention will be described in detail with
reference to the attached drawings.
[0018]
FIG. 1 is an external view showing a configuration example of a stringed instrument to which the
present invention is applied.
FIG. 2 is a plan view of the stringed instrument shown in FIG.
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5
[0019]
As shown in FIGS. 1 and 2, the stringed instrument 10 is a stringed instrument (acoustic
instrument) such as a ukulele or an acoustic guitar, for example, and a body (resonance formed
by the front plate 20, the side plate 22 and the back plate 24) Body 12 and a neck 14 connected
to the body 12.
At the tip of the neck 14 is provided a head 16 to which a plurality of pegs (thread windings) 26
capable of adjusting the tension of the chord 18 by winding the tip side (start end) of the chord
18 are attached.
The front plate 20 constituting the body 12 functions as a resonance plate.
A bridge 28 for fixing the rear end of the strings 18 is attached to the front plate 20, and the rear
ends of the strings 18 are fixed to holes or grooves (not shown) made in the bridge 28.
[0020]
Attached to the neck 14 is a fingerboard 32 in which metal frets 30 are embedded at specific
intervals.
At the tip of the finger plate 32, a nut (upper piece) 34 provided with a groove for aligning the
plurality of chords 18 at a predetermined distance and supporting the chord 18 slightly above
the upper surface of the fret 30 is fixed. It is done.
On the bridge 28, a saddle (a lower piece) 35 is fixed near the rear end (end) of the strings 18 for
supporting the strings 18 slightly above the upper surface of the frets 30.
Some types of musical instruments do not have frets 30.
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[0021]
The chords 18 vibrate between the nut 34 and the saddle 35 or between the frets 30 and the
saddle 35 on the fingerboard 32.
Further, by holding the string 18 at a predetermined place on the fingerboard 32, the string
length between the fret 30 and the saddle 35 is adjusted, and a predetermined pitch can be
obtained.
As an aspect of applying vibration to the string 18, there is an aspect of repelling the finger at a
predetermined position between the pressed finger of the string 18 and the saddle 35 or an
aspect of giving a trigger of vibration by rubbing with a bow or the like.
[0022]
Below each string 18 in front of the bridge 28 of the front panel 20, a sound hole (sound hole)
36 for guiding the sound resonated inside the body 12 to the outside is provided.
On the surface of the front plate 20 and the back plate 24 on the inner side of the body 12,
braces (force wood, sound wood) 38A and 38B for reinforcement are attached, respectively.
The shape and arrangement of braces vary depending on the type of musical instrument.
[0023]
In the above configuration, when vibration is applied to the string 18 to play the stringed
instrument 10, the vibration of the string 18 is transmitted to the front plate 20 through the
saddle 35 and the bridge 28, thereby resonating in the internal space of the body 12. The tone is
generated from the sound hole 36.
[0024]
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The stringed instrument 10 of the present embodiment is provided with a microphone unit 40
for collecting a sound resonated inside the body 12.
The microphone unit 40 is detachably attached to an end portion 12 a (an end opposite to the
neck 14 side) of the body 12 located at a distance from the sound hole 36 inside the body 12.
[0025]
FIG. 3 is a perspective view showing the configuration of the microphone unit 40. As shown in
FIG.
FIG. 4 is an exploded perspective view of the microphone unit 40 shown in FIG.
[0026]
As shown in FIGS. 3 and 4, a bolt 50 for attaching a body is provided at the tip of the microphone
unit 40. When the microphone unit 40 is attached to the body 12, the positioning nut 52 is
screwed from the tip end side of the bolt 50, and then the through hole (bolt insertion hole) 54
formed in the end portion 12 a from the inside of the body 12. Through the bolt 50. Then, the
fixing nut 60 is screwed from the tip end side of the bolt 50 through the flat washer 56 and the
spring washer 58 and tightened against the positioning nut 52, so that the microphone unit 40 is
detachably attached to the body 12 .
[0027]
In the present embodiment, the configuration in which the microphone unit 40 is detachably
attached to the body 12 is shown as an example, but there is no particular limitation as long as
they can be mechanically coupled to each other. It may be configured to be fixed using friction
without using a nut, or may be configured to be fixed using an adhesive.
[0028]
As shown in FIG. 3, the microphone unit 40 includes a condenser microphone (hereinafter
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referred to as a bi-directional microphone) 42 having bi-directionality, and a connector unit 44
for outputting an output signal of the bi-directional microphone 42.
The connector portion 44 is disposed outside the body 12 in a state where the microphone unit
40 is attached to the body 12.
[0029]
As shown in FIGS. 1 and 2, the preamplifier unit 46 is electrically connected to the connector
portion 44 of the microphone unit 40 via a cable (not shown). Thus, the output signal of the
bidirectional microphone 42 is input to the preamplifier unit 46 through the connector unit 44.
[0030]
The preamplifier unit 46 amplifies the output signal of the bidirectional microphone 42 and
outputs a signal subjected to predetermined signal processing. The output signal of the
preamplifier unit 46 is input to the external sound amplifier 48. The external sound amplification
device 48 amplifies the input signal, converts it into a sound wave, and outputs it.
[0031]
As shown in FIG. 3, the bidirectional microphone 42 is held by a resin microphone holder 64. The
bi-directional microphone 42 includes a diaphragm (diaphragm) 62 (shown by a broken line in
FIG. 3) that vibrates by sound waves, and converts the sound waves into an electrical signal and
outputs it.
[0032]
FIG. 5 is a diagram showing the directivity characteristic of the bi-directional microphone 42. As
shown in FIG. As shown in FIG. 5, the bi-directional microphone 42 has a substantially 8-shaped
directivity characteristic. That is, the direction perpendicular to the diaphragm 62 (see FIG. 3) is
taken as the directional axis (diaphragm central axis) L, and the sensitivity in the front-rear
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direction (front and back direction of the diaphragm 62) along the directional axis L is
maximized. And the sensitivity in the direction perpendicular to (the direction parallel to the
diaphragm 62) is minimal (theoretically zero).
[0033]
In the present embodiment, the direction parallel to the opening face of the sound hole 36 (ie,
the front plate 20 of the body 12) and the direction in which the sound hole 36 is formed (the
direction connecting the centers of the bidirectional microphone 42 and the sound hole 36) 5 in
the direction perpendicular to the longitudinal axis X of the stringed instrument 10). In other
words, the plane including the diaphragm 62 is arranged to intersect the sound hole 36
perpendicularly. According to such a configuration, since the sensitivity to the external sound
entering the body 12 from the sound hole 36 causing the howling becomes low, the howling can
be effectively suppressed.
[0034]
When the stringed instrument 10 is viewed from the top, the center of the sound hole 36 exists
in the longitudinal axis direction of the microphone unit 40, and the directivity axis L of the
bidirectional microphone 42 is perpendicular to the longitudinal axis direction. Thus, the
mounting angle of the microphone unit 40 (rotational angle around the longitudinal axis of the
microphone unit 40) is adjusted. The mounting angle of the bi-directional microphone 42 can be
easily adjusted by loosening the fixing nut 60.
[0035]
FIG. 6 is a block diagram showing the configuration of preamplifier unit 46. Referring to FIG. As
shown in FIG. 6, the preamplifier unit 46 includes a preamplifier 70, a frequency characteristic
correction circuit 72, and a howling suppression circuit 74. The output signal of the bidirectional
microphone 42 is amplified by the preamplifier 70 to obtain a frequency characteristic
correction circuit 72. And the signal subjected to predetermined signal processing by the howling
suppression circuit 74 is output to the external sound amplifier 48.
[0036]
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10
The frequency characteristic correction circuit 72 corrects the frequency characteristic of the
output signal of the bi-directional microphone 42 input via the preamplifier 70.
[0037]
FIG. 7 is a graph showing the frequency characteristics of the output signal of the bidirectional
microphone.
As shown in FIG. 7, the output signal of the bidirectional microphone 42 has a frequency
characteristic in which the amplitude gain increases as the frequency increases. Therefore, if the
output signal of the bi-directional microphone 42 is amplified as it is in the preamplifier unit 46
and output to the external sound amplification apparatus 48, the high frequency band is
emphasized, which causes the loss of the original timbre of the musical instrument.
[0038]
Therefore, in the present embodiment, a frequency characteristic correction circuit 72 for
correcting the frequency characteristic of the output signal of the bidirectional microphone 42 is
provided at the rear stage of the preamplifier 70. The frequency characteristic correction circuit
72 includes, for example, a gradient filter having the frequency characteristic shown in FIG. This
gradient filter has a frequency characteristic in which the amplitude gain gradually decreases as
the frequency increases. That is, the frequency characteristic correction circuit 72 includes a
gradient filter having a gradient filter having a frequency characteristic substantially opposite to
that of the bi-directional microphone 42, and outputs a signal through the gradient filter. The
frequency characteristics of the output signal of the bidirectional microphone 42 are flattened.
The signal output from the frequency characteristic correction circuit 72 is input to the howling
suppression circuit 74.
[0039]
As described above, in the present embodiment, the frequency characteristic of the microphone
is flattened by using the gradient filter having the reverse characteristic to the microphone
according to the frequency characteristic of the microphone to be used.
[0040]
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11
The howling suppression circuit 74 detects the howling frequency included in the input signal,
and outputs a signal in which the frequency component including the detected howling
frequency is suppressed.
[0041]
In the present embodiment, the directional axis L of the bi-directional microphone 42 is arranged
in a direction perpendicular to the direction in which the sound hole 36 is arranged (the
direction along the longitudinal axis X of the stringed instrument 10 in FIG. 5) The sensitivity to
the sound arriving from the sound hole 36 to the bi-directional microphone 42 can be reduced.
However, without passing through the front plate 20 of the stringed instrument 10 or the like
directly from the sound hole 36 to the bi-directional microphone 42, the sound repeatedly
reaches inside the body 12 and reaches the bi-directional microphone 42 as well. Exists.
If the sound level is high, it may not be possible to prevent howling. Also, it is conceivable that
howling may occur even when the external environment changes due to the type of instrument
or the venue.
[0042]
Therefore, in the present embodiment, in order to more reliably prevent howling caused by these
factors, the howling suppression circuit 74 is provided at the rear stage of the frequency
characteristic correction circuit 72.
[0043]
The howling suppression circuit 74 includes a notch filter 76, a notch control unit 78, and a
howling detection unit 80.
[0044]
The notch filter 76 is, for example, a filter having the frequency characteristic shown in FIG. 9,
and attenuates frequency components centered at a certain frequency (notch frequency).
04-05-2019
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The notch filter 76 is configured to be able to change the notch frequency.
The notch frequency is set in accordance with the control of a notch control unit 78 described
later.
[0045]
The howling detection unit 80 takes in the input signal (the output signal of the frequency
characteristic correction circuit 72) and detects the frequency (howling frequency) at which
howling occurs. Specifically, FFT analysis is performed on the input signal at regular intervals,
and when the peak level is equal to or higher than a predetermined level, the peak frequency is
detected and output as the howling frequency. The howling frequency output from the howling
detection unit 80 is input to the notch control unit 78.
[0046]
The notch control unit 78 controls the notch frequency of the notch filter 76 based on the
howling frequency detected by the howling detection unit 80. Specifically, control is performed
such that the notch frequency of the notch filter 76 becomes the howling frequency detected by
the howling detection unit 80.
[0047]
The attenuation amount of the notch filter 76 and the notch width (the frequency width in the
vicinity of attenuation with respect to the notch frequency) are also variable, and these are also
set according to the control of the notch control unit 78. For example, the amount of attenuation
and the notch width of the notch filter 76 may be changed by the notch control unit 78 in
accordance with the user's operation.
[0048]
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13
Further, the notch filter 76 is configured to be switchable between a valid state (on state) for
enabling the filter function having frequency characteristics as shown in FIG. 9 and an invalid
state (off state) for disabling the filter function. It is also good. When the notch filter 76 is
enabled, frequency components are removed from the input signal with the notch frequency at
the center and output. On the other hand, when the notch filter 76 is disabled, the input signal is
output as it is. The notch control unit 78 may change the notch filter 76, for example, in
accordance with the user's operation. In addition, the notch filter 76 may be in a valid state until
a predetermined time elapses after the howling detection unit 80 detects the howling frequency,
and may be in an invalid state after the predetermined time elapses. In this case, it is possible to
suppress the deterioration of the sound quality while suppressing the howling that occurs
rapidly.
[0049]
The signal output from the notch filter 76 is output to the external sound amplifier 48 as the
output of the preamplifier unit 46. The external sound amplifier 48 converts the signal output
from the preamplifier unit 46 (notch filter 76) into a sound wave and outputs it. Thus, the
musical sound of the stringed instrument 10 collected by the bi-directional microphone 42 is
amplified by the external sound amplifier 48.
[0050]
As described above, according to the present embodiment, the directional axis L of the bidirectional microphone 42 is disposed in a direction parallel to the opening plane of the sound
hole 36 and perpendicular to the direction in which the sound hole 36 is formed. Be done. That
is, since the direction in which the sensitivity of the bi-directional microphone 42 is minimum is
directed to the sound hole 36, the sensitivity to sound intruding into the body 12 from the sound
hole 36 is reduced, and howling can be effectively suppressed. It becomes possible. Further, since
the sensitivity is high except in the direction in which the sound holes 36 are formed, it is
possible to capture a wide range of sounds inside the body 12 in a well-balanced manner. As a
result, since the external sound that enters the body 12 from the sound hole 36 causing the
howling is canceled, it becomes possible to collect the musical tone that resonates inside the
body 12 without causing the howling, and the stringed instrument 10 You can faithfully
reproduce the original tones emitted by
[0051]
04-05-2019
14
In the present embodiment, the directional axis L of the bi-directional microphone 42 is disposed
parallel to the opening surface of the sound hole 36 and perpendicular to the direction in which
the sound hole 36 is formed. However, the present invention is not limited to this configuration,
and as long as the same effect can be obtained, the directional axis L may be slightly displaced as
long as it is disposed along the above direction.
[0052]
Moreover, according to the present embodiment, since the preamplifier unit 46 is provided with
the frequency characteristic correction circuit 72, the frequency characteristic of the output
signal of the bidirectional microphone 42 can be flattened.
As a result, the effect of being able to be faithfully reproduced without impairing the original
tone of the instrument can be made more remarkable.
[0053]
Further, according to the present embodiment, since the howling suppression circuit 74 is
provided in the preamplifier unit 46, the howling is suppressed by the howling suppression
circuit 74 even when howling occurs due to the external sound reflected inside the body 12.
Howling can be prevented reliably and stably. Particularly in the present embodiment, even if the
frequency at which the howling occurs changes, the howling can be suppressed while following
the change, so even when the external environment changes due to the influence of the type of
the instrument, the venue, etc. It becomes possible to suppress howling.
[0054]
Further, in the present embodiment, it is preferable that the notch filter 76 be configured to be
able to switch the filter function between the enabled state and the disabled state. If the notch
filter 76 is used unnecessarily, the frequency band centered on the notch frequency (i.e., the
howling frequency) becomes a tone that is weakened and may be different from the original tone
of the instrument. On the other hand, according to the above configuration, it is possible to
enable or disable the filter function of the notch filter 76 according to the preference of the user
and the use condition.
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[0055]
In the embodiment, the microphone unit 40 is attached to the end 12a of the body 12 (the end
opposite to the neck 14). However, the present invention is not limited thereto. You may attach
to the heel part 12b (end part by the side of the neck 14). The end portion 12a and the heel
portion 12b are the strongest places in the structure of the body 12 of the stringed instrument
10, and can stably fix the microphone unit 40. Further, since the distance between the sound
hole 36 and the microphone unit 40 can be secured, the collection efficiency of the resonance
sound in the body 12 by the microphone unit 40 can be improved.
[0056]
Further, in the present embodiment, since the output signal of the bi-directional microphone 42
is derived to the outside of the stringed instrument 10 through the connector unit 44 configured
integrally with the bi-directional microphone 42, the wiring passing through the inside of the
body 12 (Signal line) becomes unnecessary, and it becomes possible to effectively suppress noise
due to unnecessary vibration inside the body 12.
[0057]
Although the embodiments of the present invention have been described above, the present
invention is not limited to the above examples, and it goes without saying that various
improvements and modifications may be made without departing from the scope of the present
invention. .
Hereinafter, some modifications will be described.
[0058]
[Modification 1] In the embodiment described above, the preamplifier unit 46 is configured
separately from the microphone unit 40 and disposed outside the body 12, but the microphone
unit 40 has the preamplifier unit 46 built in. It is also good. In this case, the microphone unit 40
incorporating the preamplifier unit 46 is disposed inside the body 12.
04-05-2019
16
[0059]
Further, it goes without saying that when the preamplifier unit 46 is configured separately from
the microphone unit 40, the preamplifier unit 46 may be disposed inside the body 12.
[0060]
[Modification 2] In the embodiment described above, although the application to the stringed
instrument 10 in which the sound hole 36 is provided on the front plate 20 of the body 12 has
been described, depending on the type of stringed instrument, for example, as shown in FIG.
Some of the holes 36 are provided in the side plate 22 instead of the front plate 20 of the body
12.
In the stringed instrument 10 having such a configuration, as shown in FIG. 11, the directional
axis L of the bi-directional microphone 42 is parallel to the opening face of the sound hole 36
(i.e., the side plate 22 of the body 12). The holes 36 are arranged in a direction perpendicular to
the direction in which the holes 36 are formed (the direction connecting the centers of the bidirectional microphone 42 and the sound holes 36). In other words, the diaphragm (not shown in
FIG. 11) of the bi-directional microphone 42 is disposed parallel to the front plate 20 of the body
12 so that the plane containing the diaphragm intersects the sound hole 36 perpendicularly. Ru.
As a result, the sensitivity to sound entering the body 12 from the sound hole 36 is reduced, and
howling can be effectively suppressed. Therefore, the same effect as the embodiment described
above can be obtained.
[0061]
[Modification 3] In the embodiment described above, the case where the present invention is
applied to a stringed instrument having a single sound hole in a resonance cylinder such as a
ukulele or an acoustic guitar has been described. The invention can also be applied to a stringed
instrument provided with a string, such as a violin or a cello.
[0062]
DESCRIPTION OF SYMBOLS 10 ... Stringed instrument, 12 ... Body, 14 ... Neck, 16 ... Head, 18 ...
String, 20 ... Front board, 36 ... Sound hole, 40 ... Microphone unit, 42 ... Bidirectional
microphone, 46 ... Preamplifier unit, 48 ... External Sound amplification apparatus 62: diaphragm
70: preamp 72: frequency characteristic correction circuit 74: howling suppression circuit 76:
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notch filter 78: notch control section 80: howling detection section
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