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DESCRIPTION JP2016220032

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DESCRIPTION JP2016220032
Abstract: To provide a sound field reproduction system capable of reproducing a sound field with
high accuracy in a control area corresponding to each of one or a plurality of users. A sound field
control device 500 includes a plurality of speakers 530-1 and the like, a plurality of amplifiers
510-1 and the like in which gains corresponding to respective weights of the plurality of
speakers are set, and one or a plurality of users. Assuming a listening position according to the
above, it is possible to set weights corresponding to each of a plurality of speakers necessary to
realize one or a plurality of control areas using a predetermined wavefront, at least one of a
plurality of listening positions A parameter storage unit 520 for storing each combination, a
combination determination unit 522 that determines the content of the combination according to
the actual listening form by the user, and a plurality of speakers corresponding to the
determination content by the combination determination unit 522 And a parameter setting unit
526 for setting the gains of the plurality of amplifiers by reading the weights from the parameter
storage unit 520. That. [Selected figure] Figure 7
Sound reproduction system
[0001]
The present invention relates to a sound field reproduction system for controlling a sound field at
one or more listening positions included in a vehicle interior space or the like.
[0002]
In recent years, "super-realism system" has attracted attention.
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The ultra-realism system is a system that physically acquires, transmits, and reproduces the "inplace" five-sense information as physically as possible in order to bring about a feeling as if it
were in-place. The ultra-realism system is expected to be applicable to medical, educational,
artistic and various fields as well as entertainment such as movies and broadcasts.
[0003]
In order to realize a highly realistic sound system, various sound systems have been studied,
among which there is sound field reproduction technology. Sound field reproduction technology
physically reproduces the desired sound field in consideration of the wave nature of the sound,
and a higher sense of reality can be obtained for the existing sound system, and its development
is expected . Wave front synthesis, boundary sound field control, and higher order ambisonics
can be mentioned as main techniques of sound field reproduction technology.
[0004]
Wavefront synthesis (WFS) is a method of presenting sound coming from a specific direction by
reproducing the sound pressure on a plane based on the principle of Huygens. Wavefront
synthesis can be easily used as compared to other sound field reproduction techniques, and can
reproduce all the sound fields in the area enclosed by the speaker array. However, in the
wavefront synthesis method, since the boundary surface is divided and controlled, the
expressible sound direction is limited. Moreover, in order to pick up the sound field used in the
wavefront synthesis method, a microphone array is required, and there is a problem that the
installation of the array is not easy.
[0005]
Boundary sound field control (BoSC) is a method that applies the Kirchhoff-Helmholtz integral
equation and the inverse system theory. Measure the sound pressure and sound pressure
gradient on the boundary surface of the sound field area to be reproduced, and reproduce the
sound field by reproducing the sound pressure and sound pressure gradient in another space
using an inverse system Can. Boundary sound field control can not reproduce a wide range of
sound field as in the wave field synthesis method, but can reproduce the sound field with higher
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accuracy. However, because the inverse system theory is applied, the boundary sound field
control sound collection system and reproduction system have a one-to-one relationship.
Therefore, there is a point that it is difficult to use the sound field information that can be used in
the sound collection and reproduction system of boundary sound field control in another sound
collection and reproduction system of boundary sound field control. Also, for the same reason, it
can not be used for existing stereo sound sources or 5.1ch surround sound sources.
[0006]
High-order Ambisonics (HOA) is a method of representing the sound field of a boundary surface
using spherical harmonics and reproducing the sound field based on the Kirchhoff-Helmholtz
integral equation (see, for example, Patent Document 1). In high-order Ambisonics, collected
sound field information can be represented by spherical harmonic coefficients, so collected data
can be adapted to any reproduction system. Therefore, it is possible to apply this collected sound
data to existing reproduction systems such as stereo reproduction and 5.1 ch surround. It is also
possible to apply existing sound source data to Ambisonics's reproduction system. The highorder Ambisonics is expected to develop as a practical high-presence system in the future
because of its wide range of application.
[0007]
JP, 2014-161122, A
[0008]
By the way, the conventional high-order ambisonics has a problem that it can generate only one
area (control area) in which the sound field can be reproduced with high accuracy.
For example, when considering the interior space of the vehicle, it is necessary to consider not
only the driver but also other passengers as users who listen to music etc. Therefore, there are a
plurality of control areas corresponding to each user Although it is necessary, the conventional
high-order Ambisonics can provide a realistic sound field to only one user.
[0009]
The present invention has been made in view of such a point, and an object thereof is to
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reproduce a sound field which can reproduce a sound field with high accuracy in a control area
corresponding to each of one or a plurality of users. To provide a system.
[0010]
In order to solve the problems described above, the sound field reproduction system of the
present invention corresponds to each of a plurality of speakers and a plurality of speakers,
weights audio signals, and sets gains corresponding to the respective weights. Assuming the
plurality of gain adjustment means and the listening position by one or more users, the weight
corresponding to each of the plurality of speakers necessary to realize one or more control areas
using a predetermined wavefront Speaker weight storing means for storing any combination of
at least one of a plurality of listening positions; combination determining means for determining
the contents of the combination according to the actual listening form by the user; The weight of
each of the plurality of speakers corresponding to the content determined by the means is read
out from the speaker weight storage means, and the plurality of gain adjustment And a gain
setting means for setting the respective gain.
Further, it is desirable that the above-mentioned predetermined wavefront is a plane wave.
[0011]
Since it is possible to set the minimum necessary listening position according to the actual
listening form by the user, it is possible to reproduce the sound field with high accuracy in the
control area corresponding to each of one or a plurality of users. it can. In addition, when
changing the combination of listening positions, it is only necessary to read the weight of the
necessary speaker and set the gain, so it is possible to simplify the process when reproducing the
sound field.
[0012]
Further, it is desirable that the weight stored in the above-mentioned speaker weight storage
means is determined using the transfer function of the sound field between the plurality of
speakers and one or more control areas. Using the transfer function of the sound field between
each speaker and each control area, for example, applying the high-order ambisonics method of
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expressing the sound field using spherical harmonics to one or more control areas By
determining the weight of each speaker, it is possible to reproduce the sound field with high
accuracy in each control region.
[0013]
Further, it is desirable that the weights stored in the above-described speaker weight storage
means be determined by the speaker weight determination means using the transfer function
measured by the transfer function measurement means. When determining the weight of each
speaker by simultaneously applying the high-order ambisonics method of expressing the sound
field using spherical harmonics to one or a plurality of control regions, the sound is measured by
measuring the transfer function. A transfer function can be obtained in consideration of the
influence of reflection and the like generated in space, and the sound field can be reproduced
with higher accuracy in one or more control regions.
[0014]
Further, it is desirable that the above-described transfer function measurement means perform
identification of the transfer function by setting the tap coefficient of the adaptive filter using the
LMS algorithm. In particular, the transfer function measurement means described above
comprises: a measurement signal source for generating a measurement signal; an adaptive filter
to which the measurement signal is input; and a plurality of speakers for outputting the
measurement signal to an acoustic space including a plurality of control regions. A microphone
installed in a plurality of control areas and picking up sounds output from a plurality of speakers,
an operation unit calculating a difference between an output signal of the microphone and an
output signal of the adaptive filter, and outputting an error signal; A measurement signal and an
error signal are input, and it is desirable to include an LMS algorithm processing unit that sets
tap coefficients of the adaptive filter by using the LMS algorithm, and to identify the
characteristics of the adaptive filter as a transfer function. This makes it possible to measure the
transfer function accurately.
[0015]
Further, the above-mentioned speaker weight determining means may set the conversion
function matrix of high-order ambisonics as B, the weight matrix of the speaker as P, and the
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reconversion function matrix where each element is set as C by transfer function as C. It is
desirable to determine the weights of the plurality of speakers based on the relationship between
each matrix. Further, a relational expression of CP = B is established among the conversion
function matrix B, the weighting matrix P of the speaker, and the reconversion function matrix C
described above, and the speaker weight determination means determines the plurality of
speakers based on the relational expression. It is desirable to determine the weights. This makes
it possible to easily determine the weights of a plurality of speakers using the transformation
function matrix B and the retransformation function matrix C having known values.
[0016]
Further, it is preferable to further include operation means operated by the user, and the
combination determination means determines the contents of the combination in accordance
with an instruction of the user using the operation means. As a result, it becomes possible to
easily acquire the actual listening form by the user without complicating the configuration.
[0017]
In addition, it further comprises listening position detection means for detecting the listening
position of one or more users included in the predetermined detection range, and the
combination determination means combines the listening positions detected by the listening
position detection means. It is desirable to decide the content. As a result, it becomes possible to
easily acquire the actual listening form by the user without the user performing any operation.
[0018]
It is explanatory drawing which shows the spherical harmonic expression of the transfer function
C at the time of paying attention to the sound field of the plane wave seen from the origin. It is
explanatory drawing of the transfer function from the speaker to the control area | region set
other than the origin. It is explanatory drawing of the transfer function from the speaker to the
control area | region set other than the origin. It is a figure which shows the diameter of the
control area | region of the reproduced sound field. It is a figure which shows the structure of a
sound field reproduction apparatus. It is a flowchart which shows the operation | movement
procedure which determines the weight P of a speaker using the sound field reproduction
apparatus shown in FIG. It is a figure showing composition of a sound field control device of one
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embodiment to which the present invention is applied. It is explanatory drawing which shows an
example of the combination of the listening position in the case of applying the several control
area | region reproduced by this embodiment to the actual vehicle interior space. It is a figure
which shows the structure of the sound field reproduction apparatus which determines the
weight P of a speaker for every arbitrary combination K which consists of at least one of several
listening positions according to the actual acoustic space. It is a figure which shows the detailed
structure of the transfer function measurement part shown in FIG. It is a flowchart which shows
the operation | movement procedure which determines the weight P of a speaker using the
sound field reproduction apparatus shown to FIG. 9 and FIG. It is explanatory drawing which
performs C characteristic (transfer characteristic) identification. It is a figure which shows the
structure of the sound field control apparatus of a modification.
[0019]
Hereinafter, a sound field reproduction system according to an embodiment to which the present
invention is applied will be described with reference to the drawings.
[0020]
(1) The sound field of the plane wave seen from the spherical harmonics origin is
[0021]
[0022]
となる。
ここで、
[0023]
[0024]
Is a position vector indicating the position of interest,
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[0025]
[0026]
Is the wave number vector of plane waves, J n (kr) is the spherical Bessel function of the first
kind,
[0027]
[0028]
Is a spherical harmonic function.
また、
[0029]
[0030]
は、
[0031]
[0032]
となる。
また、
[0033]
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[0034]
The sound field of the plane wave seen from the
[0035]
[0036]
となる。
したがって、
[0037]
[0038]
となる。
ここで、
[0039]
[0040]
は、
[0041]
[0042]
となる。
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[0043]
next,
[0044]
[0045]
The speaker's sound field is
[0046]
[0047]
となる。
ここで、
[0048]
[0049]
は、
[0050]
[0051]
となる。
[0052]
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[0053]
Seen from
[0054]
[0055]
The speaker's sound field is
[0056]
[0057]
となる。
ここで、
[0058]
[0059]
Is as follows.
[0060]
[0061]
FIG. 1 is an explanatory view showing a spherical harmonic expression of a transfer function C
when focusing on a sound field of a plane wave viewed from an origin.
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11
In FIG. 1, M speakers L 1 to L M are arranged on the circumference around the origin, and are
conversion functions of high-order ambisonics (HOA) at the origin.
[0062]
[0063]
Is expressed by the above-mentioned equation (2).
Also, it is a transfer function from each speaker to the origin
[0064]
[0065]
Is expressed by the above-mentioned equation (9).
[0066]
(2) Basic concept of multi-area sound field reproduction Arbitrary sound field areas s 1, s 2,..., S N
of plane waves to a plurality of speakers L 1, L 2,. Use and reproduce.
Wave number vector of plane wave
[0067]
[0068]
を
[0069]
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[0070]
Then, in order to reproduce a plane wave, it is necessary to obtain the speaker weight P a for all
regions (α) and spherical harmonics (n, m) as follows.
[0071]
[0072]
よって、
[0073]
[0074]
[0075]
Is a transformation function of ordinary higher order ambisonics (HOA).
Here, assuming that the order (n) and the degree (m) of the spherical harmonics are given, the
conversion function of each reproduction area is as follows.
[0076]
[0077]
Summarizing the above equation,
[0078]
[0079]
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13
Therefore, the multiple area reproduction equation is as follows.
[0080]
[0081]
Assuming that the speaker weight is P, the high-order ambisonics (HOA) transformation matrix is
B, and the reconversion matrix is C, the matrix expression is
[0082]
[0083]
のようになる。
Here, each matrix is as follows.
[0084]
[0085]
Therefore, the weight of the speaker for reproducing the sound field is as follows.
[0086]
[0087]
A sound field can be reproduced by outputting this weight by a speaker.
[0088]
In such a method, the transfer function of the sound field from the speaker to the control area is
expressed by spherical harmonic expansion, the transfer function of each control area is
determined, and the weight of the speaker that reproduces each sound field from the transfer
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function. The sound field of a plurality of control areas is reproduced by obtaining.
[0089]
FIG. 2 and FIG. 3 are explanatory diagrams of transfer functions from each speaker to a control
area set other than the origin.
Thus, the value of each element of the inverse transformation matrix C represented by the
equation (24) can be determined by obtaining the transfer function to each of the plurality of
control regions set to other than the origin.
By this, each element on the right side of equation (25) becomes known, and it becomes possible
to determine the weight of each speaker.
[0090]
FIG. 4 is a diagram showing the diameter of the control area of the reproduced sound field.
In the example shown in FIG. 4, it can be seen that a plane wave that has arrived along the X
direction indicated by the horizontal axis is generated, and there are four places where there are
few errors.
Specifically, the control region of diameter d is reproduced at the following position.
[0091]
x = -0.5 m, y = 0.5 m: d = 24 cm x =-0.5 m, y =-0.5 m: d = 22 cm x = 0.5 m, y = 0.5 m: d = 26 cm x
= 0.5 m , Y = −0.5 m: d = 32 cm In the example shown in FIG. 4, the case where four control
areas are realized is shown, but the diameter d of these control areas is the position of each
control area. And it changes with the number.
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In particular, the smaller the number of control regions, the larger the diameter d, and the larger
the diameter d, the smaller the diameter d.
Therefore, assuming that the number of users is N and the number of control areas to be realized
in actual acoustic space is M, M is equal to N in order to set the diameter d of each control area
as large as possible. In order to secure a large diameter d, it is desirable to avoid setting many
control areas beyond the number of users.
[0092]
(3) Specific Configuration of Multi-Region Sound Field Reproduction FIG. 5 is a diagram showing
an example of the configuration of the sound field reproduction device.
The sound field reproduction apparatus 100 shown in FIG. 5 performs a process of determining
the speaker weight P based on the above-mentioned equation (25), and the control area position
setting unit 110, the operation unit 112, the transfer function setting unit 120, The HOA
function setting unit 130 and the speaker weight determination unit 140 are provided.
[0093]
The control area position setting unit 110 sets the positions of a plurality of control areas.
The operation unit 112 is configured using a numeric keypad, various knobs, a touch panel, or
the like operated by the user, and receives an input of position data or the like input by the user.
The control area position setting unit 110 described above sets the positions of a plurality of
control areas based on the user's instruction (position data) using the operation unit 112.
[0094]
The transfer function setting unit 120 expresses the transfer function of the sound field between
the plurality of speakers and the plurality of control regions by spherical harmonic expansion,
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and uses the positions of the plurality of control regions set by the control region position setting
unit 110. And sets (calculates) the transfer functions represented by the equations (11) to (13)
described above.
[0095]
The HOA function setting unit 130 sets a high-order ambisonics conversion function.
Specifically, the value of each element of the high-order Ambisonics transformation function
matrix shown by the above-mentioned equation (23) is held.
[0096]
The speaker weight determination unit 140 uses a transfer function set by the transfer function
setting unit 120 to input weights to a plurality of speakers, which are weights of a plurality of
speakers required to reproduce a plurality of control areas by plane waves. Determine weights to
weight the audio signal.
[0097]
Specifically, assuming that the transformation function matrix of the high-order ambisonics is B,
the weighting matrix of the speaker is P, and the reconversion function matrix in which each
element is set by the transfer function is C, The indicated relation is established.
The speaker weight determination unit 140 determines the weight matrix P of the plurality of
speakers based on the equation (21) and actually using the equation (25) described above.
[0098]
FIG. 6 is a flowchart showing an operation procedure of determining the speaker weight P using
the sound field reproduction apparatus 100 shown in FIG.
[0099]
First, the control area position setting unit 110 sets the positions of a plurality of control areas
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(step 100).
[0100]
Next, the transfer function setting unit 120 sets the transfer function using the positions of the
plurality of control areas set by the control area position setting unit 110 (step 102).
[0101]
Next, the speaker weight determination unit 140 is a weight of a plurality of speakers necessary
for reproducing a plurality of control regions using the transfer function set by the transfer
function setting unit 120, and is input to the plurality of speakers The weight for weighting the
audio signal to be determined is determined (step 104).
[0102]
By the way, the sound field reproduction system of the present invention assumes in advance a
combination of positions that can be the listening position of the user, and reproduces the sound
field of one or more control areas corresponding to each combination.
FIG. 7 is a diagram showing the configuration of a sound field control device according to an
embodiment to which the present invention is applied.
[0103]
The sound field control device 500 shown in FIG. 7 is connected to the output side of the audio
device 600, and M amplifiers 510-1, 510-2, ..., 510-M, parameter storage unit 520, parameter
setting The unit 526 includes a combination determination unit 522, an operation unit 524, and
M speakers 530-1, 530-2, ..., 530-M.
[0104]
Each of the amplifiers 510-1 and the like has a variable gain, and amplifies (or attenuates) the
audio signal input from the audio device 600 with a predetermined gain and outputs the
amplified signal.
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The output audio signal is input to the speaker 530-1 or the like corresponding to one to one.
[0105]
The parameter storage unit 520 assumes a listening position by one or a plurality of users, and
uses a predetermined wavefront to realize a plurality of control regions required to realize one or
a plurality of control regions corresponding to the listening position one to one. The weight
corresponding to each of the speakers 530-1 and the like is stored for each arbitrary
combination K including at least one of the plurality of listening positions.
[0106]
The combination determination unit 522 determines a combination K of listening positions in
accordance with the actual listening form by the user.
Specifically, the sound field control device 500 of the present embodiment is provided with an
operation unit 524 operated by the user, and the combination determination unit 522 responds
to the user's instruction using the operation unit 524. A combination K of listening positions is
determined.
[0107]
The amplifier 510-1 and the like mentioned above are gain adjustment means, the parameter
storage unit 520 is speaker weight storage means, the combination determination unit 522 is
combination determination means, the parameter setting unit 526 is gain setting means, and the
operation unit 524 is operation means Respectively.
[0108]
FIG. 8 is an explanatory view showing an example of a combination of listening positions in the
case where a plurality of control areas reproduced in the present embodiment are applied to an
actual vehicle interior space.
The interior space S1 shown in FIG. 8 has a plurality of seats D (for example, six seats), and the
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minimum is one driver and the maximum is one driver and five other passengers total A
combination of listening positions corresponding to the case of six persons is conceivable.
[0109]
The user selects one or more listening positions among the six seats D shown in FIG.
In this selection, the seating position of one or more users who actually listen to the audio sound
is specified.
For example, the user operates the operation unit 524 in a state where the seat diagram in which
the six seats D shown in FIG. 8 are schematically represented is displayed on the display device
(not shown), and one or more seats D is selected.
In addition, it is not necessary to necessarily use a schematic seat map, as long as the content of
the combination of "front row, middle row, back row" and "left, right" can be designated.
The combination determination unit 522 determines the combination K of the listening positions
according to the operation result of the operation unit 524.
[0110]
The parameter setting unit 526 reads respective weights of the plurality of speakers 530-1 and
the like corresponding to the combination K determined by the combination determination unit
524 from the parameter storage unit 520, and sets respective gains of the amplifier 510-1 and
the like. Do.
Specifically, corresponding to the combination K, each element P 1, P 2,..., P M which is each
element of the speaker weight matrix P determined using the above-mentioned equation (25) is It
sets as each gain of 510-1, 510-2, ..., 510-M.
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[0111]
As described above, in the sound field reproduction system according to the present
embodiment, the method of high-order ambisonics, which expresses the sound field using
spherical harmonics, is simultaneously applied to one or a plurality of control areas, and the
weight of each speaker is obtained. It becomes possible to reproduce the sound field with high
accuracy in one or more control regions by determining.
[0112]
Further, since the user operates the operation unit 524 to specify the positions of the plurality of
control areas, sound fields at the plurality of positions specified by the user can be realized with
high accuracy.
[0113]
Further, by using the equation (25) described above, it is possible to easily determine the weights
of a plurality of speakers using the transformation function matrix B and the retransformation
function matrix C having known values.
[0114]
FIG. 9 shows a sound field for determining the speaker weight P for each arbitrary combination K
of at least one of a plurality of listening positions in accordance with the actual acoustic space
(for example, the vehicle interior space shown in FIG. 8). It is a figure showing composition of a
reproduction device.
The sound field reproduction device 200 shown in FIG. 9 performs processing for determining
the speaker weight P based on the above-mentioned equation (25) for each of the plurality of
combinations K of listening positions, and the combination setting unit 210, transmission The
function measurement unit 220, the HOA function setting unit 130, and the speaker weight
determination unit 140 are provided.
The HOA function setting unit 130 and the speaker weight determination unit 140 are basically
the same as those shown in FIG. 5, and the combination setting unit 210 and the transfer
function measurement unit 220 will be described in detail below.
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21
[0115]
The combination setting unit 210 designates one of a plurality of combinations K of listening
positions, and sets one or more control areas corresponding to the designated combination K.
[0116]
The transfer function measurement unit 220 measures the transfer function of the sound field
between the plurality of speakers 530-1 and the like and one or more control regions set by the
combination setting unit 210.
The transfer function measurement unit 220 identifies the transfer function by setting the tap
coefficients of the adaptive filter using the LMS algorithm.
[0117]
The above-described transfer function measurement unit 220 corresponds to the transfer
function measurement means, and the speaker weight determination unit 140 corresponds to the
speaker weight determination means.
[0118]
FIG. 10 is a diagram showing a detailed configuration of transfer function measurement unit 220
shown in FIG.
As shown in FIG. 10, the transfer function measurement unit 220 includes a measurement signal
source 221, switches 222 and 226, a C characteristic identification unit 224, N microphones
225-1, 225-2,. 530-1, 530-2, and so on.
[0119]
The measurement signal source 221 generates a measurement signal (for example, a white noise
signal) for transfer function measurement.
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The switch 222 selectively inputs the measurement signal output from the measurement signal
source 221 to any one of the M speakers 530-1 and the like.
The C characteristic identifying unit 224 selects one of the M speakers 530-1 and the like and
one or more of the N microphones 225-1 and the like (1 to 1 listening positions included in the
focused combination K). The transfer function of the acoustic space between the corresponding
microphones) is identified.
Specific configurations and operations for identifying the transfer function will be described
later.
The switch 226 selects an output having a one-to-one correspondence with the listening position
included in the focused combination K from the outputs of the N microphones 225-1 and the
like, and inputs the selected output to the C characteristic identification unit 224.
[0120]
The arrangement of the M speakers 530-1 and the like and the N microphones 225-1 and the
like in this embodiment is actually performed using the acoustic space.
For example, in the example shown in FIG. 8, six microphones 225-1 and the like are installed at
the head position of each user when six users sit in six seats D installed in the vehicle interior
space And M speakers 510-1 and the like are installed along wall surfaces forming a vehicle
interior space so as to surround these seats.
When the combination K is designated by the combination setting unit 210, the combination K
(or information for specifying a listening position corresponding to the combination) is input to
the switch 226.
The switch 226 performs a selecting operation of inputting only the output of the microphone
225-1 or the like installed in the seat corresponding to the listening position included in the
combination K to the C characteristic identifying unit 224.
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[0121]
FIG. 11 is a flow chart showing an operation procedure for determining the speaker weight P
using the sound field reproduction device 200 shown in FIG. 9 and FIG.
[0122]
First, the combination setting unit 210 selects one from a plurality of combinations K of listening
positions (step 200).
Next, the combination setting unit 210 (or another control unit (not shown, the C characteristic
identification unit 224 may perform the same operation)) includes one control region included in
the selected combination K. While selecting one microphone 225-1 and the like corresponding to
(step 202), and one speaker 530-1 and the like (step 204).
[0123]
Next, a measurement signal is output from the measurement signal source 221 (step 206).
The measurement signal is output from the speaker 530-1 or the like selected in step 204.
[0124]
Next, the C characteristic identifying unit 224 picks up the measurement signal by the
microphone 225-1 and the like selected in step 202 (step 208), and identifies the C characteristic
(transfer function) between the selected speaker and the microphone. (Step 210).
[0125]
Next, the combination setting unit 210 determines whether there is another speaker not selected
(step 212).
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24
In some cases, an affirmative determination is made, and the process returns to step 204 and the
same identification operation is repeated for the other speakers.
In addition, when the identification operation for all the speakers is completed, a negative
determination is made in the determination of step 212.
[0126]
Next, the combination setting unit 210 determines whether there is another control area (other
microphone) not selected (step 214).
In some cases, an affirmative determination is made, and the process returns to step 202 and the
same identification operation is repeated for other control regions.
In addition, when the identification operation for all control regions is completed, a negative
determination is made in the determination of step 214.
[0127]
Next, the speaker weight determination unit 140 reproduces one or more control regions
corresponding to the combination K using a transfer function measured for all the speakers and
the combination of one or more microphones corresponding to the combination K. The weight of
the M speakers necessary for the purpose of weighting the audio signals input to the M speakers
is determined (step 216).
[0128]
Next, the combination setting unit 210 determines whether there is another combination K that
has not been selected (step 218).
If there is an unselected combination K, an affirmative determination is made, and the process
returns to step 200 to repeat the processing after the selection operation of another combination
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K.
If all combinations K have been selected, a negative determination is made in step 218, and a
series of processes for determining speaker weights for all combinations K is completed.
[0129]
Next, a specific configuration and operation for identifying the C characteristic (transfer
characteristic) will be described.
FIG. 12 is an explanatory view of performing C characteristic (transfer characteristic)
identification.
In the explanatory view shown in FIG. 12, for example, the case of identifying the C characteristic
between the speaker 530-1 and the microphone 225-1 is shown.
[0130]
As shown in FIG. 12, the C characteristic identification unit 224 includes an adaptive filter 224A,
an operation unit 224B, and an LMS algorithm processing unit 224C, and identifies the
characteristic of the adaptive filter 224A as a transfer function.
[0131]
The adaptive filter 224A is an FIR filter to which the measurement signal output from the
measurement signal source 221 is input.
The arithmetic unit 224B calculates the difference between the output signal of the microphone
530-1 and the like and the output signal of the adaptive filter 224A, and outputs an error signal
ε.
[0132]
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The LMS algorithm processing unit 224C receives the measurement signal and the error signal,
and sets the tap coefficient W (n) of the adaptive filter 224A by using the LMS algorithm as the
adaptive algorithm.
[0133]
As described above, in the sound field reproduction apparatus 200 according to the present
embodiment, the method of high-order ambisonics expressing the sound field using spherical
harmonics is simultaneously applied to a plurality of control areas to determine the weight of
each speaker By actually measuring the transfer function, it is possible to obtain a transfer
function taking into consideration the influence of reflection etc. generated in the acoustic space,
and it is possible to reproduce the sound field with higher accuracy in a plurality of control areas.
Become.
[0134]
As described above, in the sound field reproduction system according to the present
embodiment, since it is possible to set the minimum necessary listening position in accordance
with the actual listening form by the user, it corresponds to each of one or more users. The sound
field can be reproduced with high accuracy in the
Further, when changing the combination K of the listening position, it is only necessary to read
out the necessary speaker weight P and to set the gain, so that the process in reproducing the
sound field can be simplified.
[0135]
Also, the weight P stored in the parameter storage unit 520 is determined by the speaker weight
determination unit 140 using the transfer function measured by the transfer function
measurement unit 220.
By measuring the transfer function when determining the weight P of each speaker by
simultaneously applying the high-order ambisonics method of expressing the sound field using
spherical harmonics to one or more control regions, A transfer function can be obtained in
consideration of the influence of reflection and the like generated in the acoustic space, and the
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sound field can be reproduced with higher accuracy in one or a plurality of control regions.
[0136]
Further, the transfer function measurement unit 220 identifies the transfer function by setting
the tap coefficient of the adaptive filter using the LMS algorithm.
In particular, the transfer function measurement unit 220 includes a measurement signal source
221 that generates a measurement signal, an adaptive filter 224A that receives the measurement
signal, and a plurality of speakers 530 that output the measurement signal to an acoustic space
that includes a plurality of control regions. Microphone 225-1 and the like, which are installed in
a plurality of control regions, etc., and which pick up sounds output from the plurality of
speakers 530-1 and the like, an output signal of the microphone 225-1 and the like, and the
adaptive filter 224A The LMS algorithm processing of setting the tap coefficient of the adaptive
filter 224A by using the LMS algorithm and the operation unit 224B that calculates the
difference between the output signals of the two and outputs an error signal, and the
measurement signal and the error signal. Unit 224C, and identifies the characteristic of the
adaptive filter 224A as a transfer function.
This makes it possible to measure the transfer function accurately.
[0137]
Further, speaker weight determining section 140 sets each of the higher-order ambisonics
conversion function matrix to B, the speaker weight matrix to P, and the reconversion function
matrix to which each element is set to C by the transfer function is C. The weights of the plurality
of speakers are determined based on the relationship between the matrices.
Further, a relational expression of CP = B is established among the conversion function matrix B,
the weighting matrix P of the speaker, and the reconversion function matrix C described above,
and the speaker weight determination unit 140 generates a plurality of the above based on the
relational expressions. The speaker's weight P is determined.
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This makes it possible to easily determine the weights of the plurality of speakers 530-1, etc.
using the transformation function matrix B and the retransformation function matrix C having
known values.
[0138]
In addition, an operation unit 524 operated by the user is provided, and the combination
determination unit 522 determines the contents of the combination in accordance with the user's
instruction using the operation unit 524.
As a result, it becomes possible to easily acquire the actual listening form by the user without
complicating the configuration.
[0139]
The present invention is not limited to the above embodiment, and various modifications can be
made within the scope of the present invention.
For example, in the above-described embodiment, the user operates the operation unit 524 to
indicate the combination K of the listening positions, but may be detected automatically.
[0140]
FIG. 13 is a diagram showing the configuration of a sound field control device 500A according to
a modification.
A sound field control device 500A shown in FIG. 13 differs from the sound field control device
500 shown in FIG. 7 in that the operation unit 524 is replaced with a listening position detection
unit 524A.
The listening position detection unit 524A corresponds to a listening position detection unit.
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The listening position detection unit 524A is configured to include, for example, a camera for
capturing an interior space of the vehicle and an image processing unit for recognizing a head
position of a person included in the captured image.
The listening position detection unit 524A can detect which seat the user is seated on, whether
the user is an adult or a child, without the user performing a special operation.
Since the parameter storage unit 520 needs to store transfer functions measured in advance
corresponding to each listening position, the head position of the detected adult or child is not
used, but it is close to these. It is necessary to prepare representative values in advance and
select the closest representative value.
The combination determination unit 522 determines the content of the combination based on the
listening position detected by the listening position detection unit 524A.
As a result, it becomes possible to easily acquire the actual listening form by the user without the
user performing any operation.
[0141]
Further, in the above-described embodiment, although the vehicle interior space has been
described as a specific example including a plurality of control areas, the acoustic space to which
the present invention is applied may be other than these, for example, a room for home theater.
[0142]
Further, in the embodiment described above, the case of reproducing a plurality of control areas
by plane waves has been described, but the present invention can be applied to the case of
reproducing a plurality of control areas using predetermined wavefronts other than plane waves.
.
[0143]
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As described above, according to the present invention, since it is possible to set the minimum
necessary listening position according to the actual listening form by the user, the control area
corresponding to each of one or more users Can reproduce the sound field with high accuracy.
In addition, when changing the combination of listening positions, it is only necessary to read the
weight of the necessary speaker and set the gain, so it is possible to simplify the process when
reproducing the sound field.
[0144]
100, 200 sound field reproduction apparatus 110 control area position setting unit 112
operation unit 120 transfer function setting unit 130 HOA function setting unit 140 speaker
weight determination unit 210 combination setting unit 220 transfer function measurement unit
221 measurement signal source 222 switch 224 C characteristic identification Sections 225-1,
225-2, ... Microphone 500 Sound field control device 510-1, 510-2, ... Amplifier 520 Parameter
storage section 522 Combination determination section 524 Operation section 524A Listen
position detection section 526 Parameter setting section 530-1, 530-2, ... Speaker 600 audio
device
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