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JP2008154130

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DESCRIPTION JP2008154130
[Problem] In speaker installation in multi-channel audio reproduction era such as home theater,
horizontal direction and vertical direction of the speaker installation place are accurately
measured with minimum microphone array structure, and used as basic data of sound field
control. SOLUTION: A nondirectional microphone is provided in three places at each vertex of an
equilateral triangle in the horizontal direction, and a sound source arrival direction in a
horizontal plane is detected by a three-point microphone, and in the vertical direction orthogonal
to the equilateral triangle. Two nondirectional microphones are additionally installed at each
vertex of the equilateral triangle to be set, and the microphone in the forward direction is shared
by the three microphones as a shared microphone to detect the sound source arrival direction on
the vertical surface Provide an apparatus. [Selected figure] Figure 1
Sound field measurement device
[0001]
The present invention relates to a technique for measuring the installation position of a multichannel speaker to correct the sound field of an audio reproduction device.
[0002]
For audio reproduction in recent AV devices, development of home theater related technology is
active, and a plurality of speakers are arranged around the viewer to enhance realism in all
directions.
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In particular, the number of recording channels has increased due to the development of DVDs,
and a recording system of up to 13.1 channels, such as a 4-channel MUSE 3-1 system, a 5.1
channel Dolby Digital system, and a Dolby Digital Plus system, is currently proposed. In this way,
multi-channeling is progressing sequentially.
[0003]
FIG. 9 is a view showing an example of a conventional multi-channel audio reproduction
apparatus (see Patent Document 1).
[0004]
Hereinafter, the operation of the conventional multi-channel audio reproduction apparatus will
be described with reference to FIG.
[0005]
FIG. 9 shows an example of the audio reproduction method in the 5.1 channel system, and the
front L / C / R speaker and surround LS / RS speaker 24 connected to the power amplifier 23
and the power amplifier 23 for 5 channels, and the sound are shown. A field measurement
microphone array 22 and a sound field correction device 21 are provided.
[0006]
For audio reproduction in the 5.1 channel system, the ITU-R BS. The loudspeaker arrangement of
the 775-1 recommendation is recommended.
This recommends equidistant speaker installation, ± 30 ° Freon L / R speaker installation, and
± 100 ° to 120 ° surround LS / RS speaker installation.
However, in ordinary homes, it is very rare to arrange speakers at equal distances and specified
angles and maintain an environment where they can be viewed in the center, from the shape of
the room, the position of furniture such as sofas, etc. Since the viewing position is naturally
restricted, it is necessary to correct the deviation of the speaker distance, the deviation of the
volume level, and the difference of the sound quality due to the frequency characteristic
difference.
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A high level technology is required to perform these corrections, and it is a conventional multichannel audio reproduction apparatus that attempts to automatically and easily perform the
corrections.
[0007]
This operation will be described. First, an impulse signal is generated from the sound field
correction device 21, and impulse signals are sequentially output from the front L / C / R speaker
and the surround LS / RS speaker 24 through the power amplifier 23. The output impulse signal
is transmitted through the room space, collected by the microphone array 22 in which four
microphones are arranged at each vertex of the regular tetrahedron placed at the viewing
position, and inputted to the sound field correction device 21. Ru.
[0008]
FIG. 10 illustrates the difference in time for the impulse signal reproduced from the speaker 24
to reach each of the microphones of the four microphone arrays 22 installed at each vertex of
the regular tetrahedron. Assuming that it takes time t2 for the microphone 22b, time t3 for the
microphone 22c, and time t4 for the microphone 22d, the horizontal cross-correlation functions
comparable to the times t1 to t4 collected by the microphone arrays 22a to 22d are obtained.
The installation angles of the loudspeakers are determined in all directions, calculated in
comparison with the cross-correlation function based on the ideal loudspeaker position based on
the preset ITU-R recommendation shown in FIG. Correction of the distance between the speaker
and the viewing position.
[0009]
Similarly, a wobble tone is sequentially generated from the sound field correction device 21 to
perform sound pressure correction and frequency characteristic correction of each speaker.
When the audio signal of 5.1 channel input is reproduced using distance correction, sound
pressure correction, and frequency correction corrected in this way, the optimum sound field
environment close to the ideal is automatically formed easily in ordinary homes. it can. JP 2000354300 A
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[0010]
However, in the microphone array structure in which only microphones are placed at each vertex
of a regular tetrahedron, although the correct speaker position direction and distance can be
calculated in the horizontal direction, three microphones placed at the bottom of the regular
tetrahedron There is no height difference at the microphone position, so the accuracy is slightly
reduced in the vertical direction.
[0011]
As mentioned above, the number of channels in the sound field is currently up to 13.1 channels,
such as Dolby Digital Plus, from the horizontal direction, and multi-channeling is progressing
sequentially, and the sound field channels in the vertical direction are Expansion is planned.
For example, at the moment, additional channels such as top surround Ts to the ceiling, center
vertical height CVH, front LR vertical height LVH and RVH have been proposed, and it will be
necessary to measure the speaker position in the vertical direction with high accuracy. .
[0012]
The present invention solves the conventional problem of measuring the sound field in the
vertical direction, and detects the sound source arrival direction in the horizontal plane and the
sound source arrival direction in the vertical plane with a minimum microphone configuration.
The purpose is to construct a measuring device.
[0013]
In order to solve the above problems, the sound field measurement device of the present
invention comprises a microphone array in which three omnidirectional microphones can be
arranged at each vertex of an equilateral triangle in a horizontal plane and a vertical plane, and
the microphone array in a horizontal plane In the state of being disposed inside, the time
difference of the pulse sound arriving from the sound source to the three nondirectional
microphones of the microphone array is detected to detect the horizontal direction component of
the arrival direction of the pulse sound from the sound source; With the microphone array
arranged in the vertical plane, the time difference between the pulse sound arriving from the
sound source to the three nondirectional microphones of the microphone array is detected, and
the direction perpendicular to the arrival direction of the pulse sound from the sound source is
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detected. And a sound source arrival direction detection processing unit that detects a direction
component.
[0014]
Further, the sound source arrival direction detection processing unit arrives at the three
microphones from pulse sound sources distributed discretely on a spherical surface centered on
the three microphones arranged in the same shape as the microphone array. The table has a
table of time differences of pulse sounds, and the table refers to time differences of pulse sounds
arriving from the sound source to the three nondirectional microphones of the microphone array,
and the pulse sounds at the closest time difference in the table are referred to The direction of
the generation source is detected as a horizontal direction component or a vertical direction
component of the arrival direction of the pulse sound from the sound source.
[0015]
Further, the sound source arrival direction detection processing unit has a temperature sensor
for detecting the temperature of the measurement location, and the sound source from the sound
source is based on the difference between the sound velocity at the detected temperature and the
sound velocity at the temperature assumed by the table. It is characterized by having a
temperature correction processing unit which corrects the time difference of the pulse sound
arriving at the three nondirectional microphones of the array or the time difference of the table.
[0016]
In addition, the microphone array includes first three omnidirectional microphones disposed at
each vertex of an equilateral triangle in the horizontal plane and second three non-directional
microphones disposed at each vertex of the equilateral triangle in a vertical plane. 5
omnidirectional microphones having a directional microphone and sharing one of the first three
omnidirectional microphones and one of the second three omnidirectional microphones It is
characterized in that it is composed of a sex microphone.
[0017]
Further, the microphone array is characterized in that it can be changed between in the
horizontal plane and in the vertical plane by rotating the arrangement direction of the three
nondirectional microphones disposed at each vertex of an equilateral triangle by 90 °. It is a
thing.
[0018]
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The sound field correction unit further corrects the sound field of the audio signal based on the
horizontal direction component and the vertical direction component of the arrival direction of
the pulse sound detected by the sound source arrival direction detection processing unit. It is a
thing.
[0019]
The sound field measurement apparatus according to the present invention is a simple circuit of
the sound field measurement apparatus which detects the horizontal direction component of the
sound source arrival direction and the vertical direction component of the sound source arrival
direction with high accuracy with the above configuration. It can be realized by the configuration.
[0020]
The sound field measurement apparatus according to the embodiment of the present invention
detects the sound source arrival direction in the horizontal plane, that is, the horizontal direction
component of the sound source arrival direction, with microphones installed at three apexes of
an equilateral triangle on the horizontal plane. The microphones installed at the three points of
the equilateral triangle orthogonal to it detect the sound source arrival direction of the vertical
plane, that is, the vertical direction component of the sound source arrival direction, and correct
the sound speed in the real sound field by the temperature sensor. It is a sound field
measurement device capable of detecting the sound source arrival direction in the vertical
direction.
Hereinafter, embodiments of the present invention will be described with reference to the
drawings.
[0021]
First Embodiment The operation and constituent elements of the sound field measurement
apparatus according to the first embodiment of the present invention will be described in detail
below.
FIG. 1 is a perspective view showing a microphone array of a sound field measurement apparatus
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according to Embodiment 1 of the present invention.
[0022]
The microphone array of the sound field measurement apparatus according to the first
embodiment of the present invention shown in FIG. 1 is a nondirectional microphone 1 (M1), a
microphone 2 (M2), and a microphone 3 (provided at the apex of an equilateral triangle on a
horizontal surface). M3), a nondirectional microphone 4 (M4) and a microphone 5 (M5) installed
at the apex of an equilateral triangle orthogonal to the horizontal plane.
The microphone 1 is shared by the horizontal plane arrangement and the vertical plane
arrangement.
FIG. 2 is a block diagram showing a configuration of a sound field measurement apparatus which
receives the microphone array output of FIG. 1 as an input.
[0023]
The sound field measurement apparatus according to the first embodiment of the present
invention shown in FIG. 2 includes a horizontal sound source arrival direction detection
processing unit 6, a vertical surface sound source arrival direction detection processing unit 7, a
temperature sensor 8 and a temperature correction processing unit 9.
[0024]
(Method of Detecting Direction of Arrival of Sound Source in Horizontal Plane) First, a method of
detecting the direction of arrival of sound source in the horizontal plane will be described.
3A shows the sound source arrival direction in the horizontal plane of the front L speaker 10, C
speaker 11, R speaker 12, surround LS speaker 13, surround RS speaker 14 installed in the
viewing room, and the microphone array shown in FIG. FIG. 6 is a layout view showing the layout
of a microphone 1, a microphone 2 and a microphone 3 for detecting
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[0025]
In general, in order to measure the sound source distance from the viewing position to the
speaker, it is sufficient to reproduce pulse sound by the impulse signal from the speaker and
measure the arrival time thereof.
Assuming that the arrival time is τ sec and the sound velocity Vt is (331.5 + 0.6 t / ° C.) m /
sec (where t is a temperature ° C.), the distance to the speaker can be obtained by Vt × τ.
For example, at a temperature of 20 ° C., the speed of sound is 343.5 m / sec. Therefore, if the
time τ from the speaker output to the first impulse signal reaching the microphone is 10 msec,
the distance to the speaker is 343. It becomes 5 m / sec × 0.01 sec = 3.435 m.
Thus, if the impulse response is measured with one microphone, it is possible to measure the
distance to the speaker, but three or more measurements are required to determine the direction
of arrival.
That is, of the microphone arrays shown in FIG. 1, the microphones 1, 2 and 3 are used to detect
the incoming direction in the horizontal direction.
[0026]
For example, when the direction of the fluorocarbon R speaker 12 shown in FIG. 3 is measured,
the impulse signal arrives at the M1 microphone 1 after τ1, arrives at the M3 microphone 3
after τ2, and arrives at the M2 microphone 2 after τ3. This situation is shown in (a), (b) and (c)
of FIG. 4 respectively. In FIG. 4 (a), although two impulse responses are detected after the
impulse response that first arrives after τ1, it may be ignored because the later impulse
response indicates a reflected wave. . The same applies to (b) and (c).
[0027]
In the above case, since the impulse signal first arrives at the M1 microphone 1, first, the time
difference Δτ12 between τ1 and τ2 and the time difference Δτ13 between τ1 and τ3 are
measured.
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[0028]
Then, with reference to the table of sets of arrival time difference data between M1 microphone
and M2 microphone and arrival time difference data between M1 microphone and M3
microphone for various sound source arrival directions prepared in advance, to a set of Δτ12
and Δτ13 measured The sound source arrival direction of the closest data set is detected as a
horizontal component in the direction of the front R speaker 12.
[0029]
Since the above table is based on the microphone to which the impulse signal first arrives, if data
for 60 degrees to the left and right are prepared in the direction (front direction) from the center
of the microphone array toward the M1 microphone, If the microphone to which the impulse
signal first arrives is M2 or M3, the same data can be used simply by replacing the microphone
numbers.
[0030]
As an example of the data of the table, time difference data in the case where the direction of the
sound source is the direction of the angle θ from the front direction to the right will be
described with reference to FIG.
In FIG. 5, M1, M2 and M3 indicate the positions of the respective microphones, and let d be the
distance between them.
Assuming that N2 and N3 are perpendicular legs dropped from M2 and M3 on the line
connecting the sound source and M1, the distance between M1 and N2 is d · cos (30 ° −θ),
and the distance between M1 and N3 is d It is cos (30 ° + θ).
[0031]
Therefore, assuming that the sound velocity is Vt, the arrival time difference data Δτ12 to the
M1 microphone and the M2 microphone becomes Δτ12 = d · cos (30 ° −θ) / Vt, and the
arrival time difference data Δτ13 to the M1 microphone and the M3 microphone is Δτ13
Since it can be calculated as = d · cos (30 ° + θ) / Vt, a data set of Δτ12 and Δτ13 can be
calculated for any θ.
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[0032]
For this value of θ, for example, data calculated for discrete values every 10 ° between ± 60
° may be prepared.
Such an example is shown in the table of FIG. 6 where the elevation angle is 0 degrees.
FIG. 6 is a table in the case where the distance between microphones is 10 cm and the
temperature is 20 ° C., and the first sound source arriving microphone is M1. As can be seen
from the table, the data of .tau.12 and the data of .tau.13 are symmetrical with respect to 0
degree. And, when θ is +60 degrees, Δτ12 becomes 0 msec, and when −60 degrees, Δτ13
becomes 0 msec. In addition, when? Is +30 degrees, ?? 12 is maximum, and when? Is -30
degrees, ?? 13 is maximum.
[0033]
Although the above calculation example shows the case where the direction of the sound source
is on the horizontal plane including the microphone array, actually, a data set in the case where
the sound source is positioned above the horizontal plane by the elevation angle θ1 is also
necessary. Although the data set in that case is not shown in FIG. 6, since the calculation
becomes quite complicated, actually, the data set for any θ and θ1 can be obtained by
measurement including the case of θ1 = 0 degrees. Just do it. In that case, as to how to select
the values of θ and θ1, for example, as shown in FIG. 7, assuming a sound source S discretely
distributed on a spherical surface centered on the microphone array, including the microphone
array in the sound source direction The angle between the component in the horizontal direction
and the front direction may be θ, and the elevation angle of the sound source direction with
respect to the horizontal plane may be θ1. As the elevation angle θ1 increases, the
perpendicular legs N2 and N3 dropped from M2 and M3 on the line connecting the sound source
S and M1 approach M1, so the values of Δτ12 and Δτ13 decrease, and θ1 becomes + 90 °
or In the case of -90 °, that is, immediately above or below, both Δτ12 and Δτ13 become 0
msec.
[0034]
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A method of actually measuring the sound source direction using the table and the microphone
array thus prepared will be described.
[0035]
First, pulse sound is generated from the speaker to be measured.
And time (tau) 1, (tau) 2, (tau) 3 until it reaches each microphone 1, 2, 3 is measured. When τ1
is minimum, ie, when the first sound source incoming microphone is M1, the above table can be
used as it is. When τ2 is minimum, ie, when the first sound source arriving microphone is M2,
M2 may be replaced by M1, M3 by M2, and M1 by M3, and the above table may be used. When
τ3 is minimum, ie, when the first sound source arrival microphone is M3, M3 may be replaced
by M1, M1 by M2, and M2 by M3, and the above table may be used. Then, the delay time
difference sets Δτ12 and Δτ13 between the microphones are measured, the data set of the
delay time difference closest to the measured delay time difference set is retrieved from the table,
and the sound source direction to be determined is the horizontal angle θ of the retrieved data
set Component in the horizontal direction θH.
[0036]
By the way, if there is a difference between the reference temperature assumed by the above
table and the temperature at the time of measurement, an error based on the difference in the
speed of sound occurs, so it is necessary to correct this. Therefore, correction is performed using
the temperature detected by the temperature sensor 8 at the time of measurement. There are
two methods of correction. One is a method of correcting the detected time differences Δτ12,
Δτ13, etc. to become the time difference at the speed of sound at the reference temperature,
and collating the time difference after this correction with the table. Another method is a method
of correcting the time difference data of the table so as to be the time difference at the speed of
sound at the time of the measurement, and comparing the detected time differences Δτ12,
Δτ13, etc. with the table after this correction. The temperature correction unit 9 performs any
of the above corrections.
[0037]
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(Method of Detecting Direction of Arrival of Sound Source of Vertical Plane) Next, a method of
detecting the direction of arrival of sound source of the vertical surface will be described. In FIG.
3B, the sound source on the vertical surface of the front L speaker 10, the C speaker 11, the R
speaker 12, the surround LS speaker 13, the surround RS speaker 14 and the microphone array
shown in FIG. It is a figure which shows arrangement ¦ positioning of the microphone 1, the
microphone 4, and the microphone 5 which detect a direction.
[0038]
With regard to the operation of detecting the sound source arrival direction by this three-point
microphone arrangement, in the method of detecting the sound source arrival direction in the
horizontal plane, the microphone 4 is regarded as M2 and the microphone 5 is regarded as M3
and measured similarly. Let θ be the vertical direction component θV of the sound source
direction to be obtained.
[0039]
As described above, in the sound field measurement apparatus according to the first embodiment
of the present invention, the sound source arrival directions θH and θV in the horizontal plane
and the vertical plane can be estimated and calculated with a five-point microphone
configuration. Measurement is possible.
Further, as for the method of detecting the horizontal and vertical planes, the same processing
routine and delay time difference table can be used, so that the program necessary for the
process can be saved. Further, the impulse signal from the speaker does not have to be used for
horizontal plane detection and vertical plane detection, and if data from the microphone 1 to the
microphone 5 are collected at one time, the measurement time can be shortened.
[0040]
Although the sound source arrival direction is approximately obtained by the table, it is needless
to say that the equivalent distance can be calculated by the delay time of each microphone and
the angle can be obtained by the trigonometric function.
[0041]
Second Embodiment In the sound field measurement apparatus according to the second
embodiment of the present invention, three nondirectional microphones are provided at each
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vertex of an equilateral triangle in the horizontal direction, and the three-point microphone
detects the sound source arrival direction in the horizontal plane. When measuring the sound
source arrival direction in the vertical plane, the horizontal equilateral triangle is rotated by 90
° to detect the sound source arrival direction in the vertical plane, and the sound source arrival
in the horizontal plane and the vertical plane with the minimum number of microphones It
detects the direction.
[0042]
The operation and components of the sound field measurement apparatus according to the
second embodiment of the present invention will be described in detail below.
FIG. 8 is a three-dimensional view showing the microphone configuration of the sound field
measurement apparatus according to Embodiment 2 of the present invention.
[0043]
The sound field measurement apparatus according to the second embodiment of the present
invention shown in FIG. 8 includes nondirectional microphones 1, 2, 3 installed at the apex of an
equilateral triangle on a horizontal surface, and a microphone support housing 15 for supporting
the microphone array. It is.
[0044]
(Method of Detecting Direction of Arrival of Sound Source in Horizontal Plane) First, a method of
detecting the direction of arrival of sound source in the horizontal plane will be described.
The detection of the sound source arrival direction in the horizontal plane is performed by the
same means as in the first embodiment described above.
3A shows the front L speaker 10, the C speaker 11, the R speaker 12, the surround LS speaker
13, and the surround RS speaker 14 installed in the viewing room. Arrangements M1, M2, and
M3 of the microphones 1, 2 and 3 when the H measurement surface of the microphone array of
FIG. 8 is up are shown.
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[0045]
Impulse signals are sequentially generated from the speakers for horizontal detection, and the
sound source arrival direction θH in the horizontal plane is detected by the same method as the
method for detecting the sound source arrival direction in the horizontal plane described in the
first embodiment. Detailed explanations will be omitted.
[0046]
(Method of Detecting Direction of Arrival of Sound Source of Vertical Plane) Next, a method of
detecting the direction of arrival of sound source of the vertical surface will be described. The
sound source arrival direction detection on the vertical plane is performed by the same means as
in the first embodiment described above. However, in the microphone array shown in FIG. 8, the
microphone support housing 15 is rotated by 90 ° so that the microphone configuration has a
three-point configuration in the vertical direction. Similarly to the detection of the sound source
arrival direction in the horizontal plane, to explain using FIG. 3B, FIG. 3B shows the front L
speaker 10, the C speaker 11, the R speaker 12, and the surround installed in the viewing room.
The arrangement of the LS speaker 13 and the surround RS speaker 14 and the arrangements
M1, M5 and M4 of the microphone 1, the microphone 2 and the microphone 3 when the V
measurement surface of the microphone array of FIG. 8 is up are shown.
[0047]
Impulse signals are sequentially generated from the speakers for vertical detection, and the
sound source arrival direction on the vertical plane is detected in the same manner as the
method for detecting the direction from the sound source on the vertical plane described in the
first embodiment. Detailed explanations will be omitted.
[0048]
As described above, in the sound field measurement apparatus according to the second
embodiment of the present invention, the sound source arrival directions θH and θV in the
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horizontal plane and the vertical plane can be estimated and calculated with the minimum
number of microphones in the three-point microphone configuration. Because it is considered,
accurate measurement is possible. Further, as for the method of detecting the horizontal and
vertical planes, the same processing routine and delay time difference table can be used, so that
the program necessary for the process can be saved. Also, by using the impulse signal from the
speaker as horizontal plane detection and vertical plane detection, it is necessary to generate a
signal twice and twice as much measurement time is required, but the sound field measurement
device with a drastic reduction of the microphone device Can be realized.
[0049]
According to the sound field measurement apparatus according to the present invention, the
sound source arrival directions in the horizontal plane and the vertical plane can be estimated
and calculated with the minimum number of microphones, and sound velocity correction due to
temperature error can be taken into account. Sound field control is useful for measuring the
speaker position in the vertical direction as the number of channels increases, and sound field
control is particularly useful for technological development from two-dimensional only in the
horizontal plane to three-dimensional sound field control in which the vertical direction is added.
[0050]
Three-dimensional view showing a microphone array of a sound field measurement apparatus
according to Embodiment 1 of the present invention Block diagram of a sound field measurement
apparatus according to Embodiment 1 of the present invention Arrangement showing a speaker
and microphone arrangement example according to Embodiment 1 of the present invention
Figure example of impulse response waveform according to the first embodiment of the present
invention Explanatory diagram for creating a table according to the first embodiment of the
present invention Figure showing an example of delay time difference table according to the first
embodiment of the present invention Fig. 5 is a conceptual diagram showing the distribution of
sound sources for creating a table in the first embodiment. Sound source arrival direction
processing explanatory diagram of audio reproducing apparatus Diagram showing an example of
speaker arrangement of ITU-R recommendation
Explanation of sign
[0051]
1 to 5 microphones 6 horizontal sound source arrival direction detection processing unit 7
vertical surface sound source arrival direction detection processing unit 8 temperature sensor 9
temperature correction processing unit 10 L channel speaker 11 C channel speaker 12 R channel
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speaker 13 surround LS channel speaker 14 surround RS channel Speaker 15 Microphone
support housing 21 Sound field correction device 22 Microphone array 23 Power amplifier 24
Speaker
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