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JPH0937398

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DESCRIPTION JPH0937398
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound image reproducing apparatus which reproduces the same sound image as the original
sound field into a reproduced sound field by using an acoustic signal or a coded acoustic signal.
[0002]
2. Description of the Related Art FIG. 4 is a block diagram showing the configuration of a
conventional sound image reproduction apparatus, wherein 401 is an acoustic signal input
terminal to which a coded acoustic signal is input, 402 is a decoder, 403 is a reflected sound
adder, 404 is a D / A converter, 405 is a low pass filter (LPF), 406 is an amplifier, 407 is a
speaker, and 408 is a reproduction sound field.
[0003]
Next, the operation of the conventional sound image reproduction apparatus will be described.
In FIG. 4, when the encoded acoustic signal is input to the acoustic signal input terminal 401, the
input signal is decoded into a digital acoustic signal by the decoder 402, and the appropriate
reflected sound is added by the reflected sound adder 403. Be done. The signal to which the
reflected sound is added is converted to an analog signal by the D / A converter 404, the
component higher than the Nyquist frequency is attenuated by the LPF 405 which is a
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smoothing filter, amplified by the amplifier 406, and reproduced by the speaker 407. Emitted to
[0004]
As described above, even in the conventional sound image reproducing apparatus, the distance of
the sound image reproduced in the reproduction sound field 408 by appropriately setting the
delay time and the amplitude of the reflection sound added by the reflection sound adding device
403 You can control the feeling of spread.
[0005]
However, in the above-mentioned conventional sound image reproduction apparatus, when the
state of the reproduction sound field, for example, the position of the listener or the position of
the speaker changes, a sound image different from the sound image to be reproduced is received.
There was a problem that it was perceived by the listener.
[0006]
The present invention is intended to solve such conventional problems, and it is an object of the
present invention to provide an excellent adaptive sound image reproducing apparatus capable
of faithfully reproducing the sound image of the present sound field even if the state of the
reproduction sound field changes. It is said that.
[0007]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention
transmits, together with an acoustic signal, an element sense signal such as the spread, direction,
and distance of a sound image of an original sound field encoded in an auditory discrimination
unit. In the system, the microphone installed near the listener and the adaptive sound image
regenerator controlling the element sense of the sound image according to the output signal of
the microphone are provided to reproduce the sound image of the original sound field in the
reproduction sound field. The
[0008]
Therefore, according to the adaptive sound image reproducing apparatus according to the
present invention, even if the state of the reproduction sound field changes, the microphone
senses the change, and the control amount of the sound image is changed according to the
change amount. The listener has the effect of always being able to perceive the same sound
image as the original sound field.
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[0009]
Embodiments of the present invention will be described below with reference to the drawings.
[0010]
FIG. 1 is a block diagram showing the configuration of the first embodiment of the present
invention. 101 is an acoustic signal input terminal, 102 is a control signal, that is, an input
terminal of a control signal to which an element sense signal of a coded sound image is input. Is a
decoder for audio signals, 104 is a decoder for control signals, 105 and 106 are FIR filters for
control, 107, 108, 109, 110, 111 and 112 are FIR filters, 113 is an adaptive processor, and 114
and 115 are subtractions , 116: coefficient interchanger, 117: coefficient storage, 118: adaptive
sound image regenerator, 119, 120: D / A converter, 121, 122: LPF, 123, 124: amplifier, 125,
126: A / D Transducers 127 and 128 are LPFs, 129 and 130 are amplifiers, 131 and 132 are
speakers, 133 is a dummy head microphone (DHM), and 134 is a reproduction sound field.
[0011]
Next, the operation of the first embodiment will be described.
[0012]
In FIG. 1, an acoustic signal recorded in an original sound field is encoded and transmitted, and is
input to an acoustic signal input terminal 101.
The encoded acoustic signal input from the acoustic signal input terminal 101 is decoded by the
decoder 103.
The decoded signal is made to have desired amplitude and phase characteristics by the control
FIR filters 105 and 106, then converted to analog signals by the D / A converters 119 and 120,
and Nyquist frequency by the smoothing filters LPF 121 and 122. The above components are
attenuated, amplified by the amplifiers 123 and 124, radiated to the reproduction sound field
134 by the speakers 131 and 132, and reach the DHM 133 installed near the listener.
[0013]
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The coefficients of the control FIR filters 105 and 106 are updated by the adaptive processor
113.
The decoded acoustic signal is made into a target characteristic by the FIR filter 111, 112
representing the target characteristic, and becomes one input of the subtractor 114, 115.
The signal input to the DHM 133 is amplified by the amplifiers 129 and 130, the components
above the Nyquist frequency are attenuated by the LPFs 127 and 128 which are aliasing filters,
converted to digital signals by the A / D converters 125 and 126, and subtracted. It becomes the
other input of the unit 114.
The subtractor 114 calculates the difference between the target characteristic and the DHM
output signal, and inputs the difference to the adaptive processor 113.
Also, the decoded acoustic signal is characterized at the position of the DHM 133 by the FIR
filters 107 to 110 representing the transfer functions from the speakers 131 and 132 to the
DHM 133, and becomes the other input of the adaptive processor 113.
The adaptive processor 113 updates the coefficients of the control FIR filters 105 and 106
according to the input signal.
[0014]
On the other hand, the sound image perceived in the original sound field is encoded for each
discrimination limit of the element sense (spread, distance, direction) of the sound image, and is
input to the control signal input terminal 102 as a control signal.
The signal input to the control signal input terminal 102 is decoded by the decoder 104. The
coefficient replacing unit 116 reads the characteristics to be reproduced at the listener position
of the reproduction sound field 134 from the coefficient storage unit 117 and replaces the
coefficients of the FIR filters 111 and 112 according to the decoded control signal. The
coefficient storage unit 117 stores target characteristics to be reproduced for each
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discrimination limit of each element sense.
[0015]
Transfer function matrix of decoded acoustic signal is x, transfer function matrix of control FIR
filter 105, 106 is W, transfer function matrix from speaker 131, 132 to DHM 133 in reproduced
sound field 134 is C, target transfer function matrix Let W be, where d is
[0016]
If W = C to 1 · d, then
[0017]
The target characteristic can be realized at the position of the DHM 133 placed in the vicinity of
the listener, as C · W · x = d · x holds.
Further, the adaptive processor 113 updates W so that the target characteristic can be
reproduced with high accuracy even if the state of the reproduction sound field 134, that is, C
changes.
The coefficient update equation is expressed by Equation 3 according to the Filtered x LMS
algorithm.
[0018]
Where e is the output of the subtractors 114 and 115, and Wn is the transfer function matrix of
the control FIR filters 105 and 106 at the current sample, Wn +1 is the transfer function matrix
of the control FIR filters 105 and 106 at the next sample.
[0019]
As described above, according to the first embodiment, since the coefficient of the control FIR
filter is updated based on the difference between the characteristic to be reproduced at the
listener position set by the control signal and the current characteristic, Even if the condition of
the field changes, the target characteristic can always be reproduced at the listener position, and
the listener can always perceive the same sound field as the original sound field.
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[0020]
FIG. 2 is a block diagram showing the configuration of the second embodiment of the present
invention, wherein 201 is an acoustic signal input terminal, 202 is a control signal input
terminal, 203 is a decoder for acoustic signal, 204 is a direction controller, 205 is a direction
controller. A distance controller 206 is a spread controller, 207 is a decoder for control signals,
208, 209 and 210 are subtractors, 211 is a spread amount calculator, 212 is a distance amount
calculator, 213 is a direction amount calculator, 214 Is an adaptive sound image regenerator,
215 and 216 are D / A converters, 217 and 218 are LPFs, 219 and 220 are amplifiers, 221 and
222 are A / D converters, 223 and 224 are LPFs, 225 and 226 are amplifiers and 227 and 228
are speakers, 229 is a dummy head microphone (DHM), and 230 is a reproduction sound field.
[0021]
Next, the operation of the second embodiment will be described.
[0022]
In FIG. 2, an acoustic signal recorded in an original sound field is encoded and transmitted, and is
input to an acoustic signal input terminal 201.
The encoded acoustic signal input from the acoustic signal input terminal 201 is decoded by the
decoder 203.
The direction of the sound image in the reproduced sound field 230 is controlled by the direction
controller 204, the distance of the sound image is controlled by the distance controller 205, and
the spread of the sound image is controlled by the spread controller 206.
D / A converters 215 and 216 convert the signals in which the amount of sensation related to
the sound image is controlled to analog signals, the smoothing filters LPF 217 and 218 attenuate
components above the Nyquist frequency, and the amplifiers 219 and 220 amplify them. The
sound is radiated to the reproduction sound field 230 by the speakers 227 and 228, and reaches
the DHM 229 installed near the listener.
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[0023]
The signal input to the DHM 229 is amplified by the amplifiers 225 and 226, the components
above the Nyquist frequency are attenuated by the LPFs 223 and 224 which are aliasing filters,
converted to digital signals by the A / D converters 221 and 222, and spread. The value is input
to the amount calculator 211, the distance amount calculator 212, and the direction amount
calculator 213.
The spread amount calculator 211 calculates the amount of spread perceived by the listener in
the current reproduction sound field 230 from the output signal of the DHM 229 in
discrimination units, and inputs it to the subtractor 210. Similarly, the distance amount calculator
212 and the direction calculator 213 calculate the amount of distance and the amount of
direction, and input them to the subtractors 208 and 209.
[0024]
On the other hand, the sound image perceived in the original sound field is encoded for each
discrimination limit of the element sense (spread, distance, direction) of the sound image, and is
input to the control signal input terminal 202 as a control signal. The signal input to the control
signal input terminal 202 is decoded by the decoder 207. The decoded signal is one input of the
subtractors 208, 209 and 210. The subtractors 208 to 210 calculate the difference between the
element sense signal of the sound image to be reproduced and the output signals of the spread
amount calculator 211, the distance amount calculator 212, and the direction calculator 213,
and the spread controller 206 and the distance, respectively. The controller 205 and the
direction controller 204 are input. The direction controller 204, the distance controller 205, and
the spread controller 206 change the amount of controlled direction, the amount of distance, and
the amount of spread according to the difference.
[0025]
As described above, according to the second embodiment, each element is based on the
difference between the element sense amount of the sound image to be reproduced at the
listener position set by the control signal and the element sense amount of the sound image in
the current reproduction sound field. In order to change the control amount of the controller, it is
possible to always reproduce the same sound field as the original sound field even if the state of
the reproduction sound field changes.
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[0026]
FIG. 3 is a block diagram showing the configuration of the third embodiment of the present
invention, wherein 301 is an audio signal input terminal, 302 is a control signal input terminal,
303 is an audio signal decoder, 304 is a direction controller, 305 Is a distance controller, 306 is
a spread controller, 307 is a decoder for control signals, 308, 309, 310 is a subtractor, 311 is a
spread amount calculator, 312 is a distance amount calculator, 313 is a direction amount
calculator, 314 and 315 are LPFs, 316 and 317 are adders, 318 is an adaptive sound image
regenerator, 319 and 320 are D / A converters, 321 and 322 are LPFs, 323 and 324 are
amplifiers, and 325 and 326 are A / D conversions. 327 and 328 are LPFs, 329 and 330 are
amplifiers, 331 and 332 are speakers, 333 is a dummy head microphone (DHM), and 334 is a
reproduction sound field.
[0027]
Next, the operation of the third embodiment will be described.
[0028]
In FIG. 3, the operations other than the LPFs 314 and 315 and the adders 316 and 317 are the
same as those of the second embodiment.
The cut-off frequencies of the LPFs 314 and 315 are set to around 1600 Hz so that only signals
in a frequency band having a high correlation between the sense of spread of the sound image
and the sense of direction are passed.
A signal band-limited by the LPF 314 is input to the direction controller 304 and the spread
controller 306, and a signal not band-limited to the distance controller 305 is input.
Furthermore, similarly, a signal band-limited by the LPF 315 is input to the direction amount
calculator 313 and the spread amount calculator 311, and a signal not band-limited to the
distance calculator 312 is input. The adders 316 and 317 add the signal in which the sensation
amount on the band-limited sound image is controlled and the signal in which the sensation
amount on the sound image is controlled without the band limitation.
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[0029]
For this reason, in the third embodiment, in addition to the effects of the second embodiment, the
signal bands are limited by the LPFs 314 and 315, so the direction controller 304, the spread
controller 306, the spread amount calculator 311, the amount of calculation of the direction
amount calculator 313 can be reduced.
[0030]
As described above, according to the invention described in each claim, the difference between
the sound image reproduced in the reproduction sound field and the sound image to be
reproduced is calculated, and the control amount is calculated according to the difference. Since
the change is made, the sound image to be reproduced can be accurately reproduced even if the
state of the reproduction sound field changes.
[0031]
Brief description of the drawings
[0032]
1 is a block diagram showing the configuration of a first embodiment of the adaptive sound
image regenerator according to the present invention.
[0033]
2 is a block diagram showing the configuration of a second embodiment of the adaptive sound
image regenerator according to the present invention.
[0034]
3 is a block diagram showing the configuration of a third embodiment of the adaptive sound
image regenerator according to the present invention.
[0035]
4 is a block diagram showing a configuration of a conventional adaptive sound image
reproduction apparatus.
[0036]
Explanation of sign
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[0037]
101,201,301…Acoustic signal input terminal 102, 202, 302 Control signal input terminal
103, 203, 303 Decoder for acoustic signal 104, 207, 307 Decoder for control signal 105, 106
FIR filter for control 107 to 112 FIR filter 113 adaptive processor 114, 115, 208 to 210, 308 to
310 subtractor 116 coefficient replacer 117 coefficient storage 118, 214, 318 adaptive sound
image reproduction , 119, 120, 215, 216, 319, 320 ... D / A converter, 121, 122, 127, 128, 217,
218, 223, 314, 315, 321, 322, 327, 328 ... LPF, 123, 124, 129, 130, 219, 220, 220, 225, 226,
323, 329, 330 ... amplifier, 125, 126, 221, 222, 325, 326 ... A / D converter, 131, 132, 227, 228,
331, 332 ... speaker, 133, 229, 333 ... dummy head microphone (DHM), 134, 230, 334 ...
playback sound field 204, 304 ... direction controller, 205, 305 ... distance controller, 206, 306 ...
Expansion controller, 211, 311 ... Expansion amount Can, 212, 312 ... distance weight calculator,
213, 313 ... Direction amount calculator, 316, 317 ... adder.
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