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JP2007121439

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DESCRIPTION JP2007121439
The present invention provides an acoustic signal reproduction apparatus that achieves good
audible area separation by eliminating effect degradation in a low frequency range. SOLUTION:
An acoustic signal generating unit 1 for generating an acoustic signal, a first sound pressure
detection point 3 arranged at N points in an audible area to detect a sound pressure signal, and a
sound wave based on the acoustic signal To generate a control sound, a second sound pressure
detection point 5 arranged at an M point in the inaudible area and detecting a sound pressure
signal, and a sound wave based on the sound signal The first of the N control sound waves
generated by the N + 1 control sound wave generation units 4 detected by the M sound wave
generation units 6 that generate a tonic sound by emitting and the first sound pressure detection
point 3 of the N points The second sound pressure signals from the N + 1 sound wave generators
4 and the M sound wave generators 5 that are detected by the sound pressure detection point 5
at the M points while suppressing the sum of the sound pressure signals In order to minimize the
sum with the second sound pressure signal, each of the N + 1 control sound wave generators 4
And control means for controlling the amplitude and phase. [Selected figure] Figure 1
Acoustic signal reproduction device
[0001]
The present invention relates to an active noise reduction technology, and relates to an acoustic
signal reproduction apparatus for separating a sound field into an audible (non-sound reduction)
area and a non-audible (sound reduction) area.
[0002]
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1
Patent Document 1 below describes a semi-dispersed loudspeaker system in which a main sound
source speaker (main speaker) is disposed in the vicinity of a sound source and a distributed
speaker is disposed on a ceiling at a distance from the sound source.
In the same document, it is felt that sound comes from the direction of the speaker even at a
sound receiving point close to the distributed speaker (in order to obtain sound image
localization in a direction coincident with the speaker direction, It is described to control to delay.
JP 2001-112083 A
[0003]
By arranging the main sound source and the control sound source, each of which has different
distance attenuation, in proximity to the integrated structure, and reducing the sound (content
sound reproduced by the main sound source) in the vicinity of these sound sources Also, in the
audible area separation method in which the sound field is separated into the audible area and
the inaudible area, even if sound waves from both two sound sources are made to be close and
radiated to space, the sound source is used in the low frequency band (low frequency area) with
long wavelength There is a problem that noise reduction occurs from the vicinity of the sound
field, ie, the audible area, and good sound field separation ability can not be obtained.
[0004]
Therefore, in the configuration in which the main sound source speaker and the control sound
source are integrated in an integrated arrangement, the present invention eliminates the
deterioration of the effect in the low range by controlling the control sound source finely with a
plurality of amplitudes and phases. It is an object of the present invention to provide an acoustic
signal reproduction apparatus capable of realizing various audible area separation.
[0005]
An acoustic signal reproduction apparatus according to an aspect of the present invention
includes an acoustic signal generation unit that generates an acoustic signal, and a first sound
pressure detection unit that is disposed at N points (N is a natural number) in an audible area and
detects a sound pressure signal. A sound pressure signal is detected by being disposed at a point,
N + 1 control sound wave generators generating control sound by emitting a sound wave based
on the sound signal, and M points (M is a natural number) in the inaudible area The N + 1 sound
pressure detection points detected by the second sound pressure detection point, M sound wave
generators generating a tonic sound by emitting a sound wave based on the sound signal, and the
first sound pressure detection point at the N point The second sound pressure signals from the N
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+ 1 sound wave generation units, which suppress the sum of the first sound pressure signals by
the control sound generated from the control sound wave generation unit, and are detected by
the sound pressure detection points of the M points To suppress the sum with the second sound
pressure signal from the M sound wave generators And control means for controlling the (N + 1)
of each of the amplitude and phase of the control sound wave generating unit.
[0006]
According to the present invention, it is possible to provide an acoustic signal reproduction
device capable of eliminating the effect deterioration in the low frequency range and achieving
good audible area separation.
[0007]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings.
[0008]
First Embodiment FIG. 1 is a block diagram showing a functional configuration of an acoustic
signal reproduction device according to a first embodiment of the present invention.
The present apparatus includes an acoustic signal generation unit 1, a signal amplification unit 2,
a sound pressure detection point 3, a control sound wave generation unit 4, a sound pressure
detection point 5 at M points, and M sound wave generation units 6; The control calculation unit
7 includes an amplitude phase adjustment unit 8 and a time delay unit 9.
[0009]
The sound pressure detection point 3 is, for example, a microphone for detecting the sound
pressure, and N points (N is a natural number) are arranged at predetermined positions in an
audible area (non-sound reduction area).
[0010]
The control sound wave generator 4 is a speaker (control sound source) for emitting a sound
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wave of control sound, and the number of arrangement thereof is N + 1.
As described later, the control sound source is composed of any of a point sound source, a line
sound source, and a surface sound source.
The control sound is generated by processing an acoustic signal generated by the acoustic signal
generation unit 1 by the amplitude phase adjustment unit 8 and the time delay unit 9 and
amplifying the sound signal by the signal amplification unit 2.
[0011]
The sound pressure detection point 5 is, for example, a microphone for detecting the sound
pressure, and M points (M is a natural number) are arranged at predetermined positions in the
inaudible area (sound reduction area).
[0012]
The sound wave generator 6 is a speaker (main sound source) that emits a sound wave of content
sound (main sound), and the number of arrangement thereof is M.
As will be described later, the main sound source is also composed of any of a point sound
source, a line sound source, and a surface sound source.
The content sound is generated by processing an acoustic signal generated by the acoustic signal
generation unit 1 by the amplitude phase adjustment unit 8 and the time delay unit 9 and
amplifying the sound signal by the signal amplification unit 2.
[0013]
The control calculation unit 7 controls each of the control sound sources consisting of a plurality
of speakers, and at each point of the sound pressure detection point 3 consisting of N points, the
sound pressure signal from the control sound wave generation unit 4 consisting of N + 1 The
sound pressure signal from the sound wave generator 4 consisting of N + 1 pieces and the sound
pressure generator 6 consisting of M at each point of the sound pressure detection point 5 to
suppress the sum and preferably minimize Amplitude-phase and delay times are calculated to
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suppress, preferably minimize, the sum of the sound pressure signals from.
[0014]
A sound field area that forms an audible area (non-noise reduction area) around sound pressure
detection point 3 consisting of N points and an inaudible area (low sound reduction area) around
sound pressure detection point 5 consisting of M points The separation is realized by making the
sound waves having different distance attenuation rates interfere with each other by utilizing the
difference in the distance attenuation rate of each sound source.
The amplitude phase at that time is calculated by the volume velocity ratio.
[0015]
The arrangement number of sound pressure detection points 3 (= N), the arrangement number of
control sound wave generation units 4 (= N + 1), the arrangement number of sound pressure
detection points 5 (= M), and the arrangement number of sound wave generation units 6 (= M)
The relationship of) is based on the determinant described below.
The number of arranged control sound wave generators 4 is at least two or more.
Further, at least one sound pressure detection point 5 is required.
[0016]
The basic concept of controlling each of the control sound sources composed of a plurality of
speakers by the control operation unit 7 will be described below.
[0017]
[Audible Area] In the audible area, a plurality of evaluation points are set so that the sound
pressure synthetic value of the control sound source group becomes zero on the evaluation
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points.
Here, the number of control sound source groups is the number of evaluation points + 1.
Hereinafter, the case where the number of control sound source groups is N + 1 (qs1, qs2,..., QsN
+ 1) will be described.
[0018]
The evaluation points in the audible area are n1, n2, ..., nN, and the synthetic sound pressures are
Pn1, Pn2, ..., PnN.
[0019]
Thus, the sound pressure is obtained by multiplying the complex amplitude qs by the space
transfer function F, and the synthetic sound pressure P at each evaluation point can be expressed
by the following equation.
[0020]
Here, assuming that sound pressure synthesis is zero, that is, P 0 0, the second and subsequent
complex amplitudes can be expressed as in the following equation (1) using the first complex
amplitude, space transfer function, and its inverse matrix .
[0021]
ここで、
[0022]
The complex amplitude of the control sound source group is expressed by the following equation.
[0023]
[Inaudible Region] A plurality of evaluation points are set in the inaudible region, and the
synthetic sound pressure of the main sound source group and the control sound source group is
made zero on the evaluation points.
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The number of main sound source groups and the number of evaluation points are the same.
An evaluation point is set to M points, that is, the case where the number of main sound source
groups is M (qp1, qp2,..., QpM) will be described.
The main sound source qp is treated as a reference signal.
(In other words, the constant of 只) Assuming that the evaluation points in the inaudible area are
m1, m2, ..., mN, the synthetic sound pressures Qm1, Qm2, ..., QmM are expressed by the
following equation.
[0024]
Each synthetic sound pressure Q is expressed by the following equation.
[0025]
ここで
[0026]
Then, it is expressed as the following equation.
[0027]
Here, if the synthetic value of the sound pressure is zero, assuming that Q00, the complex
amplitude of the first control sound source can be expressed as the following equation (2).
[0028]
By substituting equation (2) into equation (1), qs2, qs3,..., QsN + 1 can be calculated.
[0029]
Based on the above basic concept, each of the control sound sources composed of a plurality of
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speakers closely arranged (integrally configured) to the main sound source can be controlled by
the control calculation unit 7.
In the audible area separation using the difference in the distance attenuation rate of each sound
source, as described above, the control calculation unit 7 generates N + 1 pieces of control sound
wave generation unit 4 at each point of sound pressure detection points 3 consisting of N points.
The sum of the sound pressure signals is suppressed, and at each point of the sound pressure
detection point 5 consisting of M points, sound pressure signals from the sound wave generating
part 4 consisting of N + 1 pieces and the sound pressure from the sound pressure generating
part 6 composed of M pieces By calculating and controlling the amplitude / phase and the delay
time so as to suppress the signal sum, it is possible to realize good audible area separation even
in the low tone range.
This is because the low-frequency sound has a relatively long wavelength, and the main sound
source and the control sound source are disposed close to each other, so that the propagation
path difference can not be obtained by precise control of the control sound source.
[0030]
In the realization of the acoustic signal reproduction apparatus, identification of a required space
transfer function and calculation of a control filter are required.
That is, as shown in FIG. 2, the space transfer function Fij for the audible area is identified in step
1, and the space transfer function Zij for the inaudible area is identified in step 2, and then the
control filter is calculated by the control operation unit 7. .
The calculated control filter is supplied from the control operation unit 7 to the amplitude phase
adjustment unit 8 and the time delay unit 9.
The identification of the required space transfer function and the calculation of the control filter
will be described in the second and third embodiments, respectively.
In step 3, reproduction of content sound by audible sound separation is performed.
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[0031]
Second Embodiment In the first embodiment, as shown in FIG. 1, N sound pressure detection
points 11 and M sound pressure detection points 19 are respectively suppressed, and preferably
minimized. The control filter is calculated by focusing attention on the number of sound wave
generators 4 and 6 in the above. In this embodiment, as shown in FIG. 3, it is assumed that a
plurality of sound emitting parts having the same radiation characteristics and dimensions exist
as an integral structure, and it is necessary to specifically calculate the control filter under this
condition. The process and necessary system configuration will be described.
[0032]
FIG. 3 shows an integrated speaker when the control sound source group is divided into three.
The first control sound source group 30 is arranged in a frame shape along the outer periphery
of the integrated speaker. The second control sound source 31 is a two-line linear sound source
arranged so as to sandwich the third control sound source group 32 (and the main sound source
group 33) inside the first control sound source group 30. The third control sound source group
32 is arranged in a frame shape so as to surround the main sound source group 33 inside the
first control sound source group 30. The speaker shown in FIG. 3 has an integral structure in
which speaker elements of any size and shape are combined in a matrix with an arbitrary
number, size, and shape, and as described above, the control sound source group and the main
sound source group Is selected as appropriate.
[0033]
For example, the case of three control sound source groups as described above is assumed. When
these complex amplitudes are qs1, qs2 and qs3, the evaluation points N1 and N2 in the audible
area and the synthesized sound pressures can be represented by PN1 and PN2, respectively.
Here, F sinj represents the space transfer function from the i-th control sound source to the j-th
evaluation point.
[0034]
If equation (3) is expressed again as a determinant, equation (4) is obtained.
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[0035]
Here, the following equation (5) is obtained from PN1⇒0 and PN2⇒0.
[0036]
On the other hand, in the inaudible area, it is considered to set one evaluation point so that the
synthesized sound pressure of the main sound source group and the control sound source group
becomes zero.
In the proposed condition, the number of main sound source groups is one because it is equal to
the number of evaluation points.
[0037]
Assuming that the synthetic sound pressure at the evaluation point under these conditions is Q, it
can be expressed by the equation (6) using the equation (5).
Here, Zp represents a space transfer function from the main sound source to the evaluation
point, and Zsi represents a space transfer function from the i-th control sound source to the
evaluation point.
[0038]
Therefore, assuming that the synthetic sound pressure is minimum, that is, Q⇒0, the complex
amplitude of the first control sound source can be expressed by the following formula (7) using
the complex amplitude qp of the main sound source.
[0039]
By substituting the equation (7) into the equation (5), the complex amplitudes of the second and
third control sound sources can be calculated using the complex amplitude qp of the main sound
source.
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[0040]
That is, if the amplitude of the main sound source is known, the amplitudes of the control sound
sources can also be calculated by Equations (5) and (7).
[0041]
Conventionally, in the case of a main sound source or machine noise, it is difficult to measure all
the sounding parts strictly, so it is also difficult to identify its radiation characteristics (radial
area, size, directivity, etc.).
Furthermore, it is difficult to measure all the amplitudes and phases of the sounds emitted from
these sound generation sites.
Therefore, unknown characteristics are included.
On the other hand, since the sound signal handled by the sound signal reproducing apparatus
according to the embodiment of the present invention is known, and the content is also known
from the timing sound source of the occurrence, the amplitude characteristic of the main sound
source is known. Therefore, the complex amplitudes obtained by Equation (5) and Equation (7)
can be used as they are. Therefore, if it is possible to directly obtain the space transfer functions
F and Z necessary for deriving the equations (5) and (7), it becomes possible to calculate the
control filter necessary for audible area separation.
[0042]
FIG. 4 is a functional block diagram showing means (transfer function identification means) for
identifying the space transfer functions F and Z necessary for deriving the equations (5) and (7).
[0043]
As shown in the figure, a calibration signal generation unit 10, N sound pressure detection units
11, a sound pressure signal selection unit 12 for selecting sound pressure signals from the N
sound pressure detection units 11, and a plurality of sound pressure signal selection units An
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acoustic wave transmitting unit including an acoustic wave generating unit (speaker) 13 and a
signal amplifying unit 14 and an acoustic wave transmitting unit divided into N + 1 portions 16
and sound generation for selectively generating sound from the divided portions Calculation to
calculate the transfer function based on the two parts of the part sorting unit 17, the acoustic
signal given from the calibration signal generation unit 10 to the sound wave generation unit 13
and the sound pressure signal detected by the sound pressure detection unit 11 A unit 18 is
provided.
The calculating unit 18 calculates the transfer function H ij (i = 1, 2,..., N) from the ith sounding
part 16 to the jth sound pressure detecting unit 11 (j = 1, 2,. N + 1) are sequentially identified.
[0044]
In addition, M sound pressure detection units 19, a sound pressure signal selection unit 20 for
selecting sound pressure signals from M sound pressure detection units 19, and a region 21
other than N + 1 divided sound generation regions 16 A sound generation part sorting unit 22
for generating sound selectively from the parts divided into M pieces, and an acoustic signal and
a sound pressure detection unit 19 given to the sound wave generation unit 13 from the
calibration signal generation unit 10 And a calculation unit 23 that calculates a transfer function
based on the two signals of the sound pressure signal detected by The calculation unit 23
sequentially identifies transfer functions Fiijj from the i-th sound generation part 16 and the ii-th
sound generation part 21 to the jj-th sound pressure detection part 19.
[0045]
Third Embodiment In the third embodiment, the audible area separation described in the first
embodiment is realized based on the space transfer function identified by the transfer function
identification means described in the second embodiment. The calculation (control filter
calculation means) of the control filter for performing will be described.
[0046]
FIG. 5 is a functional block diagram showing control filter calculation means.
[0047]
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As shown in the figure, the control filter calculation unit 70 calculates a control filter from the
transfer function Hij identified by the transfer function calculation unit 18 and the transfer
function Fiijj identified by the transfer function calculation unit 23.
The calculated control filter is supplied from the control filter calculation unit 70 to the control
filter calculation unit 80.
[0048]
In the configuration shown in FIG. 1, the control calculation unit 80 suppresses the sum of the
sound pressure signal from the control sound wave generation unit 4 consisting of N + 1 pieces
at each point of the sound pressure detection point 3 consisting of N points. And at each point of
the sound pressure detection point 5 consisting of M points, the sum of the sound pressure
signal from the N + 1 sound wave generator 4 and the sound pressure signal from the M sound
pressure generator 6 is suppressed, The amplitude and phase of each of the plurality of control
sound sources are controlled so as to be preferably minimized (step 3 of FIG. 2 (during
reproduction of content sound, ie, when performing audible sound separation)).
[0049]
The equations (3) and (4) shown in the second embodiment are calculated in the frequency
domain, and although the amplitude and phase of the control sound source can be calculated,
they relate to the time domain considering the control timing. There is no arrangement.
Therefore, a time delay is required to make the control sound source in time with respect to the
generation timing of the main sound source.
For this purpose, a time delay unit 9 is provided, and depending on the characteristics of the
sound source, the main sound source and the control sound source are also synchronized to
cause spatial interference between the two.
[0050]
Fourth Embodiment A fourth embodiment relates to a configuration example of a sound wave
generator (speaker).
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[0051]
The N + 1 control sound wave generator 4 shown in FIG. 1, the M sound wave generators 6, and
the plurality of sound wave generators 13 shown in FIG. 4 have a flat sound wave generation
surface as shown in FIG. And curved surface shapes.
The sound wave generation part having a flat sound wave generation surface includes a
rectangular one 60, a frame (leak) one 61, a wire (bar) one 62 and the like. The sound wave
generation portion having a curved sound wave generation surface includes those 63 and 64
which are obtained by cutting off a part of a cylinder. In the sound wave generation unit having a
curved sound wave generation surface, by changing the curvature, it is possible to adjust time
delay, amplitude, and phase using the difference in distance to the sound receiving point.
[0052]
As shown in FIG. 7, the distance attenuation of the sound largely varies depending on the size
and shape of the radiation surface in the vicinity of the sound source, but the distance
attenuation at the distant part is approximately constant regardless of the size and shape. It has a
feature. FIG. 7 is a graph showing the relationship between the distance [m] from the sound
source and the sound pressure (difference). The curve C1 is the point sound source 70 and the
curve C2 is the line sound source 71. Curve C3 is the case where the sound source is the planar
sound source 72. As can be seen from the figure, the attenuation rates are similar in the distance,
and spatial interference of sound waves is likely to occur. For example, the point sound source
70 is used as a main sound source for reproducing content, and in this case, the line sound
source 71 and the surface sound source 72 are used as a control sound source.
[0053]
In addition, even in the case of a sound wave generation unit having the same surface, the
difference in distance is different depending on the size of the surface and the position of the
sound receiving point, whereby the time delay, amplitude, and phase also have different
characteristics. In the case of a curved surface, the difference in distance is larger than in the
case of a planar surface, and the time delay, the amplitude, and the phase difference are also
large. This is shown in FIGS. 8 (a) and 8 (b). FIG. 8A shows the case where the sound wave
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generation surface is a plane, and FIG. 8B shows the case where the sound wave generation
surface is a curved surface. The case of FIG. 8 (a) where the sound wave generator 80 and the
control sound generator 81 are integrally flat and the case of FIG. 8 (b) where the sound wave
generator 80 and control sound generator 81 are integrally curved are shown. In contrast, the
distance difference Δrc> the distance difference Δrc. As a result, the degree of interference
decreases around the N sound pressure detection points 3 nearby because the initial phase is
different.
[0054]
By combining this principle with the principles described in the first to third embodiments, an
audible area (non-noise reduction area) is formed around the N sound pressure detection points
3 in the vicinity, and An inaudible area (sound reduction area) that sharply reduces sound can be
formed around the sound pressure detection point 5 of the point, and sound field area separation
can be realized.
[0055]
FIG. 9 is a model diagram when the present invention is applied to a television.
9 (a) shows an example of a configuration in which the sound source 91 is disposed at the lower
end of the television 90, FIG. 9 (b) shows an example of a space-saving configuration in which the
sound source 92 is disposed at the lower end of the television 90, FIG. FIG. 9 (d) shows a
configuration example in which a cylindrical sound source 94 is disposed on the side portion of
the television 90, respectively.
[0056]
10 and 11 respectively divide the control sound wave generator (control sound source group) 4
into two or three in the six-row, eight-column integrated speaker (FIG. 3) according to the first to
fourth embodiments described above It is a figure which shows the control result in the case. FIG.
10 (a) shows a model when the control sound source group is divided into two, FIG. 10 (b) shows
a sound pressure reduction amount, and FIG. 10 (c) shows a sound pressure distribution chart. In
this model, a point sound source group consisting of four speakers is provided at the center of
the integrated speaker. The control sound source group is divided into two, a first control sound
source group arranged to surround the outer periphery of the four point sound source groups
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and a second control sound source group arranged at the outermost periphery of the integrated
speaker. There is.
[0057]
FIG. 11 shows the case where the control sound source group is divided into three. In this model,
a point sound source group consisting of four speakers is provided at the center of the integrated
speaker. The control sound source group includes a first control sound source group arranged to
surround the outer circumferences of the four point sound source groups, a second control
sound source group arranged at the outermost circumference of the integrated speaker, and a
first control. The first control sound source group is divided into three, and a third control sound
source group consisting of two lines of linear sound sources disposed in the gap between the
sound source group and the second control sound source group.
[0058]
As can be seen from FIGS. 10 and 11, the sound pressure transition / distribution of the control
field changes according to the number of divisions of the control sound source group and the
selected place. Comparing FIG. 10 with FIG. 11, it can be seen that the sound pressure drop in
the audible area is lower in the case of FIG. 11 (three divisions), and a preferable characteristic is
obtained.
[0059]
The present invention is not limited to the above embodiment as it is, and at the implementation
stage, the constituent elements can be modified and embodied without departing from the scope
of the invention. In addition, various inventions can be formed by appropriate combinations of a
plurality of constituent elements disclosed in the above embodiment. For example, some
components may be deleted from all the components shown in the embodiment. Furthermore,
components in different embodiments may be combined as appropriate.
[0060]
FIG. 6 is a block diagram showing the functional configuration of the sound signal reproducing
apparatus according to an embodiment of the present invention; FIG. 6 shows the procedure for
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calculating the control filter; Means for showing functional block diagram Control filter
calculation means Functional block diagram Sound wave generator (speaker) Diagram showing
various configuration examples due to difference in shape of sound wave generation surface
Distance from sound source [m] and sound pressure (difference) A graph showing the
relationship between the sound wave generation section (speaker) and the distance difference
due to the difference in the shape of the sound wave generation surface of the model. The
present invention is applied to a television. FIG. 6 shows a control result when the control sound
source group is divided into two FIG. 6 shows a control result when the control sound source
group is divided into three in FIG.
Explanation of sign
[0061]
Reference Signs List 1 acoustic signal generation unit 2 signal amplification unit 3 sound
pressure detection point 4 control sound wave generation unit 6 sound wave generation unit 7
control operation unit 8 amplitude phase adjustment unit 9 Time delay unit
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