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DESCRIPTION JP4341851

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DESCRIPTION JP4341851
Abstract: A sound radiated from a rear surface of a speaker is reflected in an enclosure and
vibrates on a rear surface of a cone, whereby a sound with modulation distortion of phase shift is
emitted to the outside. Mute the reflected sound. SOLUTION: A main speaker 5a and a subspeaker 5b having the same characteristics are coaxially arranged in a close distance on a first
chamber 3a which is a rectangular parallelepiped configured point-symmetrically, and
electrically driven with opposite polarity. In the speaker device, the sub-speaker 5b functions as
an active muffling speaker to muffle the bass on the back of the main speaker 5a. The sound
above medium noise on the back of the main speaker 5a is absorbed by the sound absorbing
material 4 provided on the entire surface inside the first chamber 3a. The sound traveling
straight from the back of the sub-speaker 5b toward the back of the main speaker 5a is absorbed
by the central surface sound absorbing material 4a to suppress the vibration to the back of the
main speaker 5a cone by the sound wave of the phase shift due to the distance difference
between the speaker arrangements lose. [Selected figure] Figure 1
Speaker device
[0001]
The present invention relates to a speaker device that mutes a sound emitted from the back of
the speaker by passive muffling and active muffling.
[0002]
The methods of silencing the sound according to the prior art can be roughly classified into two.
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Passive muffling and active muffling.
[0003]
The first passive silencer uses a sound absorbing material, a sound absorbing board, a reflector,
and the like. As a speaker device, there are a closed type using a sound absorbing material, a bass
reflex type, a back load horn type using a reflection plate, a double bass reflex type, and the like.
Outside the speaker device, there are a muffler, a soundproof panel and the like.
[0004]
The second active muffling is to generate a sound with the same sound pressure and antiphase
sound and muffle by interference of the waves, especially for muffling of bass (representing a
sound of 200 Hz or less, hereinafter referred to as bass) It is effective. In the speaker device, it
can be said that the bass is actively muffled in the enclosure in one type of tandem speaker
device for bass reinforcement. Outside the speaker device, an engine exhaust noise reduction
device provided with a dedicated DSP (digital signal processing) control device, an air conditioner
duct noise reduction device, an indoor noise reduction device of an automobile, and the like have
been put to practical use.
[0005]
The sound absorbing material used in passive noise reduction is remarkable in sound absorption
at high sound (representing a sound of 2 KHz or higher, hereinafter referred to as high sound),
but in medium sound (representing a sound of 200 Hz to 2 KHz, hereinafter referred to as middle
sound) The effect decreases gradually as it gets lower. Adding sound-absorbing material in the
enclosure is not particularly effective in bass, and the bass repeats reflections in the enclosure
and is repeatedly converted to heat energy and vibrates the back of the speaker cone until the
sound disappears. Due to this, in the conventional speaker device, the sound radiated to the
outside is a sound accompanied by modulation distortion of phase delay several times.
[0006]
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As a remedy, mid and low frequencies below 1.5 KHz that are radiated from the back of the
speaker that radiates sound to the outside are actively muted, and mid and high tones above 1.5
KHz are muted with the sound absorbing material. And mute the sound emitted from the back of
the speaker (hereinafter referred to as the external speaker) that radiates the sound to the
outside.
[0007]
The specific measures for actively muting mid and low frequencies lower than 1.5 KHz will be
described.
In the tandem type speaker device of a system in which speakers having the same physical and
electrical characteristics as the external speakers are coaxially arranged back to back inside the
enclosure and vibrated in the same direction, the speakers arranged inside the enclosure By
using the sound of antiphase same sound pressure emitted from the back of the internal speaker
(hereinafter referred to as internal speaker) as the control sound of the active muffling, the
internal speaker functions as an active muffling speaker and the back sound of the external
speaker is activated. Mute.
[0008]
However, using the internal speaker of the tandem type speaker device as an active noise
reduction speaker causes a new problem. There is a distance between the installation of the
external and internal speakers. Due to this, when the internal speaker back sound goes straight to
the back of the external speaker and reaches the back of the external speaker (wave
independence by the principle of wave superposition), 1.5 KHz or more (external speaker and
internal speaker installed (Depending on the distance between them) is to vibrate the cone on the
back of the external speaker with this out-of-phase sound with a phase shift of 180 ° or more in
mid-tone and high-tone tones.
[0009]
In order to suppress this vibration, a tandem-type speaker device in which internal speakers are
arranged in the direction perpendicular to the external speakers has also been put to practical
use, but it is difficult to eliminate interference, and the active noise reduction efficiency
decreases.
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[0010]
According to the present invention, as shown in FIG. 1, a central surface sound absorbing
material 4a is provided on the central surface of the main speaker 5a and the sub speaker 5b,
and a sound absorbing effect is generated by the central surface sound absorbing material 4a
from the 500 Hz medium sound radiated from the back surface of the sub speaker 5b. To
suppress or eliminate the vibration of the rear face of the main speaker 5a cone with a sound of
500 Hz or more.
[0011]
Japanese Patent Application Laid-Open No. 2002-369289 discloses a similar configuration in the
present invention, a method of configuring an enclosure, a method of installing a speaker, a point
of using the same speaker, and a method of driving a speaker.
According to the publication, one of the problems to be solved by the invention is "preventing
peaks and valleys of sound pressure frequency characteristics caused by phase interference
between speakers".
The problem is to be solved by reducing the volume of the enclosure in which the speakers are
installed back to back.
[0012]
In the speaker device according to the present invention, the medium sound and the bass with a
frequency lower than 1.5 KHz radiated from the back surface of the external speaker actively
generate the wave interference by the sound of the antiphase sound pressure radiated from the
back surface of the internal speaker Use and actively mute. Medium and high tones of 1.5 KHz or
more emitted from the back of the external speaker are silenced passively by the sound
absorbing material in the enclosure. The combination of these active muffling and passive
muffling is characterized in that the back sound of the external speaker is muffled.
[0013]
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The speaker device according to the present invention solves the problem of vibrating the cone
on the back of the external speaker due to the sound wave of phase shift due to the difference in
distance between the external speaker and the internal speaker by absorbing the sound by the
central surface sound absorbing material 4a. . Unexamined-Japanese-Patent No. 10-224891
[0014]
The problem to be solved is that the sound emitted from the back of the speaker is reflected in
the enclosure, and the reflected sound vibrates on the back of the cone and the sound with the
modulation distortion of the phase shift is emitted to the outside .
[0015]
In order to solve such a problem, in the invention of claim 1, the enclosure 1 is a sealed
rectangular parallelepiped formed of a front baffle plate 1a, a top plate 1b, a base plate 1c, a
back plate 1d and left and right side plates. A first chamber 3a, which is a sealed rectangular
solid surrounded by a front baffle plate 1a, an inner baffle plate 2a, a top plate 1b, an inner lower
plate 2b and left and right side plates, a front baffle plate 1a, an inner baffle plate 2a, A sealed
second chamber 3b surrounded by the back plate 1d, the top plate 1b, the inner lower plate 2b,
the base plate 1c and the left and right side plates is provided, and the volume of the second
chamber 3b is formed larger than the volume of the first chamber 3a. The first chamber 3a is
configured to be point-symmetrical at the center point, and the inner surface is provided with the
sound absorbing material 4 on all surfaces except the speaker mounting hole, and the front baffle
plate 1a or the inner baffle plate 2a of the first chamber 3a Central plane parallel to The central
speaker 4a is provided, the main speaker 5a is disposed forward on the front baffle plate 1a, and
the auxiliary speaker 5b having the same physical and electrical characteristics is provided on
the inner baffle plate 2a coaxially on the main speaker 5a. In the speaker device disposed back to
back at a close distance, the electrical connection of the main speaker 5a and the sub speaker 5b
is connected to the audio amplifier with a reverse polarity, and the sub speaker 5b functions as
an active muffling speaker.
[0016]
According to the conventional speaker device, only the sound absorption by the sound absorbing
material and the passive sounding which repeatedly muffles the reflection inside the enclosure
are the muffling of the back sound of the speaker that radiates the sound to the outside, and the
muttering measures for the bass are not taken The
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[0017]
According to the present invention, the active noise reduction is introduced into the speaker
device, the low frequency sound radiated from the back of the speaker emitting the sound to the
outside is actively silenced, and the sound more than the medium sound is silently silenced by
the sound absorbing material. There is an advantage that the modulation distortion of the
speaker which radiates the sound by the reflected sound to the outside is eliminated.
[0018]
The speaker device according to the present invention is low in cost by realizing active noise
reduction without providing a dedicated DSP controller for bass in the enclosure, and an existing
audio amplifier can be used.
[0019]
FIG. 1 is a side cross-sectional view of a speaker apparatus showing a first embodiment of the
present invention, and the second chamber 3b is formed with a volume equal to or larger than a
predetermined volume of a closed type according to the characteristics of the sub speaker 5b.
Although the L-shaped octahedron is used to reduce the depth of the enclosure 1 in this figure, a
change to a rectangular parallelepiped or a spindle is possible.
In addition, the back-load horn type is formed according to the Q0 value of the sub-speaker 5b.
[0020]
The first chamber 3a is formed of a sealed rectangular parallelepiped, and the volume is
determined by arranging the main speaker 5a and the sub speaker 5b coaxially back to back at
an extremely close distance.
The volume of the first chamber 3a is smaller than the volume of the second chamber 3b.
[0021]
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The main speaker 5a and the sub-speaker 5b are speakers having the same physical and
electrical characteristics, and are electrically connected to the audio connector so that the
polarities of the main speaker 5a and the sub-speaker 5b are opposite as shown in FIG. Do.
Therefore, the sound radiated from the back surface of the main speaker 5a and the back surface
of the sub-speaker 5b has an opposite phase and the vibration direction becomes the same.
[0022]
The second chamber 3b is formed of a volume equal to or greater than a predetermined volume
of the closed type according to the characteristics of the sub-speaker 5b, and the volume of the
first chamber 3a is less than the volume of the second chamber 3b. When driving 5a and subspeaker 5b, the air pressure on the front of main speaker 5a and the air pressure on the front of
sub-speaker 5b become approximately equal, and the sound emitted from the back of main
speaker 5a and the sound emitted from the back of sub-speaker 5b Is approximately the same
sound pressure.
[0023]
The first chamber 3a is configured to be point-symmetrical at a central point.
That is, the physical structure is plane-symmetrical in the central plane of the front baffle plate
1a and the inner baffle plate 2a, and the physical structure is plane-symmetrical in the central
plane of the top plate 1b and the inner lower plate 2b.
Therefore, between the speakers (the sound to be emitted is at the tip position of the cone
regardless of the frequency, and in the first chamber 3a, represents the space from the tip
position of the main speaker 5a cone to the tip position of the sub speaker 5b cone) The reflected
sound of the sound radiated from the back of the main speaker 5a and the reflected sound of the
sound radiated from the back of the sub-speaker 5b are maintained in opposite phase and
approximately at the same sound pressure.
[0024]
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When the traveling direction of medium and bass sounds lower than 1.5 KHz radiated from the
back of the main speaker 5a is the top plate 1b or the inner lower plate 2b or the side plate
direction, primary reflected sound or secondary reflected sound of the sound.・ Or the sound
paths of the n-th reflection and the 1st or second-order reflection of medium and low-pitch
sounds lower than 1.5 KHz emitted from the back of the sub-speaker 5b or the n-th reflection are
shown in FIG. When it is on the shown coaxial space (two examples in the coaxial space are
shown by thick lines and thin lines), or when it is on the near parallel space shown in FIG. And
the antiphase, approximately equal sound pressure, and the directivity in the frequency range of
1.5 KHz or less are not sharp, and nearby sound waves are actively muffled.
[0025]
In the inside of the first chamber 3a, by providing the sound absorbing material 4 on all surfaces
except the speaker attachment holes, the traveling directions of medium and high sound of 1.5
KHz or more radiated from the back of the main speaker 5a and the back of the sub speaker 5b.
When the direction is the top plate 1 b or the inner lower plate 2 b or the side plate direction, the
reflected sound is absorbed by the sound absorbing material 4.
[0026]
When the sound radiated from the back of the auxiliary speaker 5b travels straight to the back of
the main speaker 5a and reaches the back of the main speaker 5a, a phase difference occurs with
the sound emitted from the back of the main speaker 5a.
This phase difference increases as the frequency increases.
There are a position where sound cancellation occurs between the speakers and a position where
sound increase occurs (which indicates that the sound pressure increases due to the interference
of two or more sound waves, hereinafter referred to as sound increase) due to this phase
difference.
[0027]
Assuming that the linear distance between the speakers is A and the wavelength of the light
radiated from the main speaker 5a is λ, the average of the muffling amount between the
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speakers and the volume increase is muffled, A = (λ / 2) The amount of muffling and the
increase in sound volume are equal, and when A> (λ / 2), muffling does not necessarily occur.
Therefore, in order to mute to a high frequency, the main speaker 5a and the sub-speaker 5b are
disposed as close as possible.
[0028]
The center plane of the first chamber 3a when the middle sound and the high sound of A> (λ /
2) which are not necessarily muffled between the speakers radiated from the back of the subspeaker 5b go straight to the back of the main speaker 5a. By providing the sound absorbing
material 4a, medium and high sounds of A> (λ / 2) can be absorbed, and vibration of the back of
the main speaker 5a cone can be eliminated.
[0029]
Even if the frequency of the sound radiated from the back of the sub-speaker 5b toward the back
of the main speaker 5a is A <(λ / 2) and the noise is reduced between the speakers, the sound
pressure decreases, but reaches the back of the main speaker 5a Then, the back of the main
speaker 5a cone is vibrated by the phase delayed sound.
In order to suppress this vibration, a central surface sound absorbing material 4a provided on the
central surface uses a thick sound absorbing material (t = 20 mm or more), such as glass wool
having high sound absorption effect to a low frequency, high performance cotton material and
the like.
[0030]
In the prototype of 8 cm full range use according to the present invention, the linear distance
between the speakers is 11.5 cm, and the frequency with a silencing effect is up to 1,496 Hz
from the bass. However, when the straight sound radiated from the back of the auxiliary speaker
5b reaches the back of the main speaker 5a, the phase difference with the sound on the back of
the main speaker 5a is, for example, 85 ° at 700 Hz and the back of the main speaker 5a cone is
in phase. Receive vibration with delayed sound. When the sub-speaker 5b of the tandem type
speaker device is used as an active muffling speaker, it is important not to generate distortion in
the sound of the main speaker 5a which radiates to the outside as well as the muffling effect. The
central plane sound absorbing material 4a absorbs the sound in the frequency range from about
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500 Hz (about 60 ° phase difference). In this prototype, high-performance cotton material that
can absorb sound down to low frequencies is used thick (t = 30 mm).
[0031]
FIG. 2 is a side sectional view of the speaker apparatus showing the embodiment 2 of the present
invention. The purpose of the embodiment 2 is not for reproducing a wide frequency band, and
the frequency band to be reproduced is limited to human voice. Is a speaker device suitable for
PA (paprick address) such as local broadcasting which requires more clarity. The same parts as in
the first embodiment are denoted by the same reference numerals.
[0032]
The configuration of the second embodiment is the same as the configuration of the first
chamber 3a of the first embodiment.
[0033]
The main speaker 5a and the sub-speaker 5b are speakers having the same physical and
electrical characteristics, and the installation method and the electrical connection method are
the same as in the first embodiment.
[0034]
When the main speaker 5a and the sub-speaker 5b are driven, the air pressure on the front of
the main speaker 5a and the air pressure on the front of the sub-speaker 5b are the same
pressure, and the sound emitted from the back of the main speaker 5a and the back of the subspeaker 5b The sound has the same sound pressure.
[0035]
The reflection of the sound radiated from the back of the main speaker 5a is actively muffled by
the reflection of the sound radiated from the back of the sub-speaker 5b, or the explanation of
the fact that the sound absorbing material absorbs the sound is described in the first
embodiment. It is omitted because it is the same as
[0036]
The explanation of eliminating or suppressing the vibration of the cone on the back of the main
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speaker 5a by the straight sound radiated from the back of the sub speaker 5b to the back
direction of the main speaker 5a is the same as that of the first embodiment, and therefore will
be omitted.
[0037]
It is a sectional side view of the speaker apparatus which showed Example 1 of this invention.
It is a sectional side view of the speaker apparatus which showed Example 2 of this invention.
FIG. 7 is an explanatory view showing a method of connecting the main speaker 5a, the sub
speaker 5b, and the audio amplifier.
It is a figure showing an example where sound reflections are muffled on coaxial space.
It is a figure showing an example in which reflected sounds are muffled on near parallel space.
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