JP2003111198A - Audio signal processing method and audio reproduction system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To localize a sound image at an arbitrary position outside the listener's head, it is possible to reduce the circuit scale and the amount of calculation of the signal processing for sound image localization, and to provide a sound image with a sufficient sense of distance. To be able to be localized. In a correction circuit, a transfer function HLL from a sound image position at which an audio signal Dl is localized to a listener's left ear is provided.
And the transfer function HCL from the set sound image position to the left ear of the listener is corrected. The correction circuit 32 corrects the sound signal Dl from the sound image position at which the sound signal Dl is localized to the right ear of the listener. , And the transfer function HCR from the set sound image position to the right ear of the listener is corrected. The same applies to the audio signal Dr. Digital filter 37L
Implements a transfer function HCL, and the digital filter 37R implements a transfer function HCR.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio signal processing method for localizing a sound image at an arbitrary position, and a sound reproducing system for localizing a sound image at an arbitrary position.

[0002]

2. Description of the Related Art Recently, multi-channel audio signals are often used for audio accompanying images such as movies, and the screens on which the images are displayed, speakers placed on both sides and the center of the display, and behind or on both sides of the listener. It is recorded assuming that it will be played back by a speaker placed next to it. As a result, the sound source in the video and the sound image position actually heard coincide with each other, and a sound field having a natural spread can be obtained.

However, when such a sound is viewed through headphones, the sound image by the input sound signal is localized in the listener's head, and the image position and the sound image localization position do not match,
The sound image localization becomes extremely unnatural, and the sound image localization positions of the audio signals of the respective channels cannot be separated and independent.

The same applies to the case where only multi-channel sound such as a musical sound is watched, and when listening through headphones, unlike a case where the sound is reproduced through a speaker, the sound is heard from the inside of the head and the sound image of the multi-channel audio signal is obtained. The localization position does not separate, resulting in extremely unnatural sound field reproduction.

Therefore, when listening to a voice with headphones, a sound image is localized at an arbitrary position outside the listener's head so that a sound field equivalent to that when a speaker is arranged at that position is obtained. A playback system is being considered.

FIG. 16 shows the principle thereof, in which the listener 1 wears the headphones 3 and the left and right acoustic transducers 3L, 3 are provided.
This is a case where the sound is heard by R and the sound image of the stereo input sound signal is localized at an arbitrary position outside the listener's head, for example, at positions indicated by sound sources 5L and 5R symmetrical with respect to the median plane 2 in front of the listener.

In this case, the left and right speakers are arranged in advance at the positions of the sound sources 5L and 5R, and the left and right sounds output from the left and right speakers are measured at the positions of the left and right ears 1L and 1R of the listener 1 or calculated. The transfer function HL from the sound source 5L to the left and right ears 1L and 1R of the listener 1.
Left and right ears 1 of listener 1 from L, HLR, and sound source 5R
Transfer functions HRL and HRR that reach L and 1R are obtained.

FIG. 17 shows a conventional audio reproduction system in the case of FIG. 16, in which left and right input analog audio signals Al and Ar corresponding to the signals of the sound sources 5L and 5R of FIG. 16 supplied to terminals 11 and 13, respectively. But A / D (Anal
og to Digital) converters 21 and 2
3 is converted into digital audio signals Dl and Dr, the digital audio signal Dl is supplied to digital filters 91 and 92, and the digital audio signal Dr is supplied to digital filters 93 and 94.

Digital filters 91 and 92 respectively convolve the digital audio signal Dl with impulse responses as shown in FIG. 18 obtained by converting the above transfer functions HLL and HLR on the time axis. And 94 are convolutions of the digital audio signal Dr with impulse responses as shown in FIG. 18, which are obtained by converting the transfer functions HRL and HRR on the time axis.

The digital filters 91 to 94 are, for example,
FIR (Finite) as shown in FIG.
An Impulse Response) filter. That is, in this case, the audio signal supplied to the input terminal 61 is sequentially delayed by the delay circuits 62 connected in multiple stages for the delay time of the sampling period τ, and the multiplication circuits 63 input the audio signal and the delay circuits. The output signal of 62 is multiplied by the coefficient, and in each addition circuit 64,
The output signals of the multiplication circuits 63 are sequentially added, and the output terminal 6
The audio signal after filtering is obtained in FIG.

As shown in FIG. 20, the digital filter 91 and the digital filter 92, and the digital filter 93 and the digital filter 94 share the delay circuit 62, respectively, to form the digital filter 91 or 93. 63 and an adder circuit 64, and a multiplier circuit 67 and an adder circuit 68 forming a digital filter 92 or 94 are provided, the input digital audio signal Dl or Dr is supplied to the input terminal 61, and the digital filter 91 or 93 to the output terminal 65. Output signal DLL or D
It is also possible to adopt a configuration in which RL is obtained and the output signal DLR or DRR of the digital filter 92 or 94 is obtained at the output terminal 69.

Then, in the audio reproduction system of FIG.
The adder circuit 95L adds the output signals DLL and DRL of the digital filters 91 and 93, and the adder circuit 95L
R is the output signal DL of the digital filters 92 and 94
R and DRR are added to add circuits 95L and 95L.
The digital audio signals DL and DR at the output of R are D / A
(Digital to Analog) Converter 4
The analog audio signals are converted into analog audio signals by 1L and 41R, and the two systems of analog audio signals are amplified by the audio amplifier circuits 42L and 42R and supplied to the left and right acoustic transducers 3L and 3R of the headphones 3.

Therefore, in the audio reproduction system of FIG. 17, the transfer functions HLL and HRL are realized by the system of the digital filters 91 and 93, and the transfer functions HLR and HRR are realized by the system of the digital filters 92 and 94. Left and right input audio signals Al (Dl) and Ar
The sound image by (Dr) is localized at the positions of the sound sources 5L and 5R.

In FIG. 16, the right and left ears 1L, 1 of the listener 1 are connected to the sound sources 5L, 5R at positions symmetrical with respect to the median plane 2.
Assuming that the transfer characteristic to R is symmetric, that is,
Assuming that HLL = HRR and HLR = HRL,
The audio reproduction system can be configured with two digital filters, as shown in FIG.

That is, in the audio reproduction system of FIG. 21, the audio signal D from the A / D converters 21 and 23 is
l and Dr are added by the adder circuit 96a and subtracted by the adder circuit 96b to obtain the adder circuits 96a and 96b.
Is supplied to the digital filters 97a and 97b, the output signals of the digital filters 97a and 97b are subtracted by the adding circuit 98a, and the adding circuit 98b is added.
Then, the output signals of the addition circuits 98a and 98b are added to form the audio signals DL and DR supplied to the acoustic transducers 3L and 3R of the headphones 3.

The digital filters 97a and 97b are
One convolves the impulse response obtained by converting the transfer function HLL = HRR on the time axis, and the other convolves the transfer function HLR = HR.
This is a convolution of the impulse response obtained by converting L on the time axis.

On the other hand, when the sound is reproduced by the speaker, there is a problem in that the layout of the speaker is limited, and a large number of speakers for reproducing the multi-channel sound can be installed in the listening room.

Therefore, it is considered that a small number of speakers, for example, two speakers are used to localize a large number of sound images based on multi-channel input audio signals at arbitrary positions around the listener.

FIG. 22 shows the principle thereof. For example, the speakers 6L and 6L are arranged at positions symmetrical with respect to the median plane 2 in front of the listener.
6R is arranged and the sound image of the input audio signal SO is localized at an arbitrary position around the listener 1, for example, the left rear position shown by the sound source 5O.

In this case, the input sound signal SO which is the signal of the sound source 5O and the drive signals SL and SR of the speakers 6L and 6R.
The relationship with is represented by SL = HL × SO (21a) SR = HR × SO (22a).

HL and HR are speakers 6 respectively.
Transfer function H from L to the left and right ears 1L and 1R of the listener 1
Left and right ears 1 of listener 1 from LL, HLR, speaker 6R
Transfer functions HRL and HRR leading to L and 1R, and sound source 5
Transfer function H from O to the left and right ears 1L and 1R of the listener 1
As a function of OL and HOR, the transfer function represented by the term multiplied by the signal SO in the equations (21) and (22) of FIG. 22 is considered so as to cancel the crosstalk between the speakers 6L and 6R. It is a thing. Transfer function HLL,
HLR, HRL, HRR, HOL, HOR are obtained in advance by measurement or calculation.

FIG. 23 shows a conventional audio reproduction system in the case of FIG. 22, in which an input analog audio signal SOa supplied to a terminal 11 is converted into a digital audio signal SOd by an A / D converter 21, and the digital audio signal SOd is converted. Signal SOd
Are supplied to the digital filters 99L and 99R.

The digital filters 99L and 99R are
The transfer function H is added to the digital audio signal SOd.
The impulse response obtained by converting L and HR on the time axis is convoluted. For example, as shown in FIG. 24, each is configured by an FIR filter as shown in FIG.

Further, as shown in FIG. 25, the digital filters 99L and 99R share the delay circuit 62,
A multiplication circuit 63 and an addition circuit 64 that configure the digital filter 99L, a multiplication circuit 67 and an addition circuit 68 that configure the digital filter 99R are provided, and the input terminal 61 is provided.
Input sound signal SOd is supplied to the output terminal 6
The output signal SLd of the digital filter 99L can be obtained at 5, and the output signal SRd of the digital filter 99R can be obtained at the output terminal 69.

Then, in the audio reproducing system of FIG.
The digital audio signals SLd and SRd output from the digital filters 99L and 99R are transferred to the D / A converter 41.
Analog audio signals SLa and SRa at L and 41R
Are converted into analog audio signals SLa and SRa
Is amplified by the audio amplifier circuits 42L and 42R and supplied to the speakers 6L and 6R.

Therefore, in the audio reproduction system of FIG. 23, the transfer functions HL and HR are the digital filters 99.
Realized by the system of L and 99R, the input audio signal SO
The sound image of (SOa, SOd) is localized at the position of the sound source 5O.

FIG. 23 shows the case where the sound image of the input audio signal of one channel is localized at one sound source position.
By providing a signal processing unit for sound image localization consisting of two digital filters 99L and 99R as shown in FIG. 3 for multi-channel input audio signals, two speakers 6
With L and 6R, a large number of sound images by multi-channel input audio signals can be localized at arbitrary positions around the listener.

[0028]

However, as shown in FIG.
17 requires a pair of sufficiently long impulse response data for the input audio signal of each channel in the audio reproduction system of FIG. When the section is configured by a hardware circuit, the circuit scale becomes large, and when the signal processing section for sound image localization is configured to include software (processing program), the amount of calculation increases and the load on the CPU is increased. Grows larger.

On the other hand, in the audio reproduction system of FIG. 21, a pair of impulse response data may be used for the input audio signals of two channels, and the circuit scale and the amount of calculation of the signal processing for sound image localization can be reduced. .

However, in the audio reproduction system of FIG. 21, the transfer characteristics from the sound sources 5L, 5R at positions symmetrical with respect to the median plane 2 to the left and right ears 1L, 1R of the listener 1 in FIG. 16 are symmetrical. Therefore, the left and right reflected waves cannot be independently configured, and the impulse response is such that the reflected waves come only from directly in front of or behind the listener 1, resulting in a far distance in front of or behind the listener 1. There is a drawback that the sound image cannot be localized at the position.

Further, even in the audio reproducing system of FIG. 23 based on the principle of FIG. 22, when audio is reproduced by the two speakers 6L and 6R, a pair of sufficiently long impulse response data is provided for the input audio signal of each channel. This increases the circuit scale and the amount of calculation for signal processing for sound image localization.

Therefore, according to the present invention, when the sound image is localized at an arbitrary position, the circuit scale and the amount of calculation of the signal processing for sound image localization can be reduced, and the sound image is localized with a sufficient sense of distance. It was made possible.

[0033]

According to the audio signal processing method of the present invention, a transfer function of an input audio signal from the sound image position to be localized to the left ear of the listener and the set sound image position to the left ear of the listener. According to the difference with the transfer function, after the correction process, for the reproduction of the transfer function from the set sound image position to the left ear of the listener, the input sound signal is subjected to the filtering process, and the input sound signal is localized at the sound image position. According to the difference between the transfer function from the listener to the right ear of the listener, and the transfer function from the set sound image position to the listener's right ear, after correction processing, from the set sound image position to the listener's right ear Filtering is performed to reproduce the transfer function.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION In the following, as a first to a fourth embodiment, a case where a voice is heard by headphones will be shown.
As a fifth embodiment, a case where sound is reproduced by a speaker will be described.

[First Embodiment ... FIGS. 1 and 2] FIG.
Shows the principle of the present invention when listening to sound through headphones, in which the listener 1 wears the headphones 3 and
The sound is listened to by the left and right acoustic transducers 3L and 3R, and the sound image of the stereo input audio signal is shown at arbitrary positions outside the listener's head, for example, sound sources 5L and 5R symmetrical with respect to the midplane 2 in front of the listener. This is the case where the position is localized.

In this case, apart from the sound sources 5L and 5R, as a representative sound image position, for example, a position in front of the median plane indicated by the sound source 5C is set.

Left and right ears 1L, 1 of the listener 1 from the sound source 5C
Transfer functions HCL and HCR reaching R, transfer functions HLL and HL reaching the left and right ears 1L and 1R of the listener 1 from the sound source 5L
R and left and right ears 1L and 1R of the listener 1 from the sound source 5R
The transfer functions HRL and HRR leading to are obtained in advance by measurement or calculation.

FIG. 2 shows an embodiment of the audio reproduction system of the present invention in the case of FIG. 1, and the left and right inputs corresponding to the signals of the sound sources 5L and 5R of FIG. 1 are supplied to terminals 11 and 13. Analog audio signals Al and Ar
The D converters 21 and 23 convert the digital audio signals Dl and Dr, and the digital audio signals Dl and D
The r is supplied to the signal processing unit 30.

The signal processor 30 uses a dedicated DSP (Dig
A sound image localization control unit 51 including the correction circuits 31 and 32 and a sound image localization control unit including the correction circuits 33 and 34 functionally as a device including software (processing program) by an italical processor or the like or as a hardware circuit. 53, adder circuits 35L and 35R, and digital filters 37L and 3
The correction circuits 31 to 34 are controlled by the sound image localization position information Sc, which is information indicating the position of the sound image localized by 7R, that is, the position (direction and distance with respect to the listener 1) of the sound sources 5L and 5R in FIG.

Then, the digital audio signal Dl from the A / D converter 21 is supplied to the correction circuits 31 and 32, and the digital audio signal Dr from the A / D converter 23 is supplied.
To the correction circuits 33 and 34, and the addition circuit 35L
Output signals of the correction circuits 31 and 33
rL is added, and the output signals DlR and DrR of the correction circuits 32 and 34 are added by the adder circuit 35R to output the output signals DcL and DcR of the adder circuits 35L and 35R.
It is supplied to the digital filters 37L and 37R.

Furthermore, digital filters 37L and 3L
7 / R output digital audio signals DL and DR
The A converters 41L and 41R convert into analog audio signals, and the two systems of analog audio signals are amplified by the audio amplifier circuits 42L and 42R and supplied to the left and right acoustic transducers 3L and 3R of the headphones 3.

The correction circuit 31 receives the input digital audio signal D
It is assumed that a correction process corresponding to the transfer function ratio shown in the equation (1) of FIG. 1 is performed on l, and the correction circuit 32 shows the input digital audio signal Dl by the equation (2) of FIG. The correction circuit 3 performs correction processing corresponding to the transfer function ratio.
3 performs a correction process on the input digital audio signal Dr corresponding to the transfer function ratio shown in the equation (3) of FIG. 1, and the correction circuit 34 performs the correction process on the input digital audio signal Dr of FIG. It is assumed that a correction process corresponding to the transfer function ratio shown in the equation (4) is performed. Specifically, the correction circuits 31 to 34
Is configured as described below.

The digital filter 37L includes the adder circuit 35.
A transfer function HCL from the sound source 5C of FIG. 1 to the left ear 1L of the listener 1 is converted to an L output signal DcL on the time axis,
Suppose that the impulse response as shown in FIG. 3 is convoluted,
The digital filter 37R convolves the output signal DcR of the adder circuit 35R with an impulse response as shown in FIG. 3, which is obtained by converting the transfer function HCR from the sound source 5C of FIG. 1 to the right ear 1R of the listener 1 on the time axis. And

The digital filters 37L and 37R are
For example, as shown in FIG. 4, each is constituted by an FIR filter as shown in FIG.

In the audio reproduction system of FIG. 2 described above, the system of the correction circuit 31 and the digital filter 37L allows
A transfer function HLL from the sound source 5L of FIG. 1 to the left ear 1L of the listener 1 is realized, and the correction circuit 32 and the digital filter 3 are provided.
7R, a transfer function HLR from the sound source 5L of FIG. 1 to the right ear 1R of the listener 1 is realized, and the correction circuit 33
1 and the digital filter 37L realize a transfer function HRL from the sound source 5R of FIG. 1 to the left ear 1L of the listener 1, and the system of the correction circuit 34 and the digital filter 37R realizes the transfer function HRL of FIG. A transfer function HRR reaching the right ear 1R of is realized.

Therefore, the left and right input audio signals Al (D
The sound images of 1) and Ar (Dr) can be localized at the positions of the sound sources 5L and 5R.

Moreover, two digital filters 37L and 37R are provided for the input audio signals of two channels.
It is only necessary to obtain a pair of sufficiently long impulse response data, and the correction circuits 31 to 34 only perform the correction processing corresponding to the transfer function ratios shown in the equations (1) to (4) of FIG. Since the transfer characteristics from different sound sources to the same ear of the listener have very similar characteristics, the correction circuits 31 to 34 make the circuit scale significantly smaller than the digital filters 37L and 37R, and significantly reduce the amount of calculation. Can be reduced. Therefore, as a whole, the circuit scale and the amount of calculation of the signal processing for sound image localization can be reduced.

In general, the transfer function includes elements such as signal delay and attenuation in the transmission path, and frequency characteristics of the transmission path. With regard to sound image localization, the delay time most affects the sense of localization.

Therefore, the correction circuits 31 to 34, for example,
As shown in FIG. 5, each of them is configured by a delay circuit 55, and the delay time of the delay circuit 55 of the correction circuits 31 to 34 is set by the sound image localization position information Sc described above.

Specifically, a delay circuit 55 of the correction circuit 31 realizes a difference in time required for the tones to reach the left ear 1L of the listener 1 from the sound sources 5L and 5C of FIG. The delay circuit 5 of the correction circuit 32 calculates the difference in the time required to reach the right ear 1R of the listener 1 from the sound sources 5L and 5C.
5, the delay time 55 required for the tones to reach the left ear 1L of the listener 1 from the sound sources 5R and 5C of FIG. 1 is realized by the delay circuit 55 of the correction circuit 33.
The delay circuit 55 of the correction circuit 34 realizes the difference in time required to reach the right ear 1R of the listener 1 from the sound sources 5R and 5C.

Further, the correction circuits 31 to 34 are constituted by a delay circuit 55 and an attenuation circuit 56, respectively, as shown in FIG. 6, and the correction circuits 31 to 34 are delayed by the sound image localization position information Sc. The delay time of the circuit 55 and the attenuation ratio of the attenuation circuit 56 are set.

By also considering the attenuation of the signal, the sound image can be localized at a desired position more reliably.

Further, the correction circuits 31 to 34 are constituted by a delay circuit 55 and a frequency characteristic correction circuit 57, respectively, as shown in FIG. 7, and the correction circuits 31 to 34 are made based on the sound image localization position information Sc. Delay circuit 55
The delay time and the frequency characteristic of the frequency characteristic correction circuit 57 are set.

In general, as the position of the sound source is further away from the listener's median plane in the left-right direction, the high frequency component of the signal reaching the listener's ear decreases.

In the example of FIG. 7, the sound image position to be localized (see FIG.
By controlling the frequency characteristic correction circuit 57 according to the positions of the sound sources 5L and 5R, the localization feeling closer to the actual localization feeling can be obtained.

The frequency characteristic correction circuit 57 is, for example, as shown in FIG.
As shown in, the input voice signal Sin is delayed by the delay circuit 71a.
And 71b, the output audio signal Sout is sequentially delayed by τ, and the output audio signal Sout is sequentially delayed by τ by delay circuits 72a and 72b.
a, 74b, 75a, and 75b, the input audio signal Sin and the delay circuits 71a, 71b, 72a, and 72b, respectively.
Is multiplied by a coefficient, and the addition circuit 76
The multiplication results of 3,74a, 74b, 75a, and 75b are added, and the addition result is taken out as the output audio signal Sout. Multiplier circuits 73, 74a, 74b, 75
The coefficients a and 75b are set according to the sound image positions (the positions of the sound sources 5L and 5R in FIG. 1) to be localized by the sound image localization position information Sc described above.

Further, the correction circuits 31 to 34 are, for example,
Each of them is configured by an FIR filter as shown in FIG.

That is, in this case, the audio signal supplied to the input terminal 81 is sequentially delayed by the delay circuits 82 connected in multiple stages with the delay time of the sampling period τ, and the input audio signal and The output signal of each delay circuit 82 is multiplied by a coefficient, and the output signal of each multiplication circuit 83 is sequentially added by each addition circuit 84 to obtain an audio signal after filtering at the output terminal 85. The coefficient of each multiplication circuit 83 is set in accordance with the sound image localization position (the positions of the sound sources 5L and 5R in FIG. 1) by the sound image localization position information Sc described above.

In this case, the FIR filters forming the correction circuits 31 to 34 are for correcting the transfer function and are different from the FIR filters forming the digital filters 37L and 37R as shown in FIG. It is not necessary to obtain response data, and a low-order filter with about 100 taps may be used.

By configuring the correction circuits 31 to 34 by the FIR filter as described above, more accurate sound image localization can be performed.

The sound image position set as the representative sound image position is not common to the input sound signals of the respective channels as shown by the sound source 5C in FIG. The input audio signals may be located separately, for example, symmetrically with respect to the median plane 2.

The input audio signal may be one channel. In this case, the input audio signal is filtered by a pair of digital filters such as digital filters 37L and 37R and then corrected by a pair of correction circuits such as correction circuits 31 and 32 or correction circuits 33 and 34, respectively. can do.

[Second Embodiment ... FIG. 10] FIG. 10 shows another embodiment of the audio reproducing system according to the present invention.
Is another embodiment for listening to a stereo audio signal through headphones as described above.

In this embodiment, the addition circuit 35 is used without setting a typical sound image position as shown by the sound source 5C in FIG.
At L, the input digital audio signal Dl from the A / D converter 21 and the output signal of the correction circuit 33 are added, and the addition circuit 3
At 5R, the input digital audio signal Dr from the A / D converter 23 and the output signal of the correction circuit 32 are added, and the output signals of the addition circuits 35L and 35R are added to the digital filter 3
7L and 37R, and the correction circuit 33
Is a transfer function ratio H with respect to the input digital audio signal Dr.
It is assumed that the correction processing corresponding to RL / HLL is performed, the correction circuit 32 performs the correction processing corresponding to the transfer function ratio HLR / HRR for the input digital audio signal Dl, and the digital filter 37L is added to the addition circuit. The output signal of 35 L is convoluted with the impulse response obtained by converting the transfer function HLL on the time axis, and the digital filter 37 R
Is convoluted with the output signal of the adding circuit 35R by the impulse response obtained by converting the transfer function HRR on the time axis.

The correction circuits 32 and 33 have the configurations shown in FIG. 5, FIG. 6, FIG. 7 or FIG. 9, respectively.
Others are the same as the embodiment of FIG.

Therefore, in the audio reproduction system of FIG. 10, the transfer functions HLL and HRL from the sound sources 5L and 5R of FIG. 1 to the left ear 1L of the listener 1 are changed by the system of the correction circuit 33, the addition circuit 35L and the digital filter 37L. The transfer functions HLR and HRR from the sound sources 5L and 5R of FIG. 1 to the right ear 1R of the listener 1 are realized by the system of the correction circuit 32, the addition circuit 35R, and the digital filter 37R, and the left and right input audio signals Al ( Dl) and Ar
The sound image generated by (Dr) can be localized at the positions of the sound sources 5L and 5R.

Moreover, in this embodiment, only two correction circuits are required for two-channel input audio signals, and the circuit scale and the amount of calculation of the signal processing for sound image localization can be further reduced.

[Third Embodiment ... FIG. 11] In the embodiments of FIGS. 2 and 10, the case where two-channel audio signals are listened to by the headphones is used. It can also be applied when listening by.

FIG. 11 shows an embodiment of this case,
The digital audio signals Da, Db, Dc, Dd, and De are input audio signals that localize a sound image at an arbitrary position outside the listener's head.

The input audio signals Da to De are supplied to the correction circuits 31 and 32 of the sound image localization control units 51a to 51e, and the addition circuit 35L causes the sound image localization control units 51a to 51e.
The output signals of the correction circuit 31 of FIG.
Then, the output signals of the correction circuit 32 of the sound image localization control units 51a to 51e are added, and the output signals of the addition circuits 35L and 35R are supplied to the digital filters 37L and 37R.

The correction circuits 31 and 32 of the sound image localization control units 51a to 51e respectively receive the input audio signal Da similarly to the correction circuits 31 and 32 or 33 and 34 of the embodiment of FIG.
1 to De are subjected to a correction process corresponding to the transfer function ratio corresponding to the sound image position to be localized, and the digital filters 37L and 37R are similar to the digital filters 37L and 37R of the embodiment of FIG. Transfer functions HCL and HCR from the sound source 5C to the left and right ears 1L and 1R of the listener 1
Shall be realized.

In the conventional method shown in FIG. 17, a digital filter capable of obtaining sufficiently long impulse response data requires a filter having twice the number of channels of the input audio signal. On the other hand, in the embodiment of FIG. 11, only two digital filters are required to obtain sufficiently long impulse response data regardless of the number of channels of the input audio signal. It is possible to reduce the circuit scale and the amount of calculation of the signal processing for sound image localization as compared with the method described in (1).

Moreover, the digital filters 37L and 37R
Since the sound image of the input audio signal of each channel is localized by the same data of the output signals DL and DR of 1, the uniform sound quality can be obtained between the channels.

[Fourth Embodiment ... FIGS. 12 and 13]
FIG. 12 shows another embodiment in which a multi-channel audio signal is heard by headphones.

In this embodiment, as shown in FIG.
The sound images of the input audio signals Da and Db are localized at the positions indicated by the sound sources 5A and 5B that are symmetric with respect to the front midline of the listener, and the sound source 5 that is symmetric with respect to the midline of the rear of the listener is located.
The sound images of the input audio signals Dd and De are localized at the positions indicated by D and 5E. The sound source 5 is a typical sound image position.
A position on the front side of the median plane indicated by C and a position on the rear side of the median side indicated by the sound source 5F are set.

Sound sources 5A, 5B, 5D, 5E, 5C, 5F
Transfer function HLL, HR from the listener to the left ear 1L of the listener 1
L, BLL, BRL, HCL, BCL, and sound source 5
Transfer functions HLR, HRR, BLR, BRR from A, 5B, 5D, 5E, 5C, 5F to the right ear 1R of the listener 1,
HCR and BCR are obtained in advance by measurement or calculation.

In the audio reproduction system of FIG. 12, the input audio signals Da, Db, Dd and De are input to the sound image localization control section 51.
a, 51b, 51d, 51e correction circuits 31 and 32
The output signal of the correction circuit 31 of the sound image localization control units 51a and 51b is added by the addition circuit 35L, and the output signal of the correction circuit 32 of the sound image localization control units 51a and 51b is added by the addition circuit 35R. The adder circuit 36L adds the output signals of the correction circuits 31 of the sound image localization control units 51d and 51e, and the adder circuit 36R adds the sound image localization control unit 51d.
And the output signals of the correction circuit 32 of 51e are added, and the output signals of the addition circuits 35L, 35R, 36L, 36R are supplied to the digital filters 37L, 37R, 38L, 38R.

The sound image localization control units 51a, 51b, 51d,
The correction circuits 31 and 32 and the digital filters 37L, 37R, 38L and 38R of 51e are the sound sources 5C of FIG.
Of the sound source 5A, 5B by utilizing the position of the sound source 5A, 5B
A signal processing unit that localizes the sound images of the input audio signals Dd and De to the positions of the sound sources 5D and 5E using the position of F is provided in parallel.

In this embodiment, the input audio signals Da, D
The sound image localization for b, Dd, and De,
Sound sources 5A, 5B and 5D, which are sound image positions to be localized,
Since the sound source positions 5C and 5F, which are close to the position 5E, are used, the sound image localization control units 51a, 51b and 51
The correction amounts at d and 51e can be reduced, and highly accurate sound image localization can be performed.

[Fifth Embodiment ... FIGS. 14 and 15]
FIG. 14 shows an embodiment of the audio reproduction system of the present invention when audio is reproduced by a speaker.

In this embodiment, for example, as shown in FIG. 15, the speakers 6L and 6R are arranged at positions symmetrical with respect to the median plane in front of the listener, and the sound image of the stereo audio signal is
Arbitrary position around the listener 1, for example, sound sources 5L, 5R
It is localized at a position symmetrical with respect to the median plane in front of the listener indicated by.

In this case, the transfer functions FLL and FLR from the speaker 6L to the left and right ears 1L and 1R of the listener 1, the transfer functions FRL and FRR from the speaker 6R to the left and right ears 1L and 1R of the listener 1, and the sound source 5L to the listener. The relationship between the transfer functions HLL and HLR reaching the left and right ears 1L and 1R of the listener 1 and the transfer functions HRL and HRR reaching the left and right ears 1L and 1R of the listener 1 from the sound source 5R is as shown in equations (11) to (1) of FIG.
4).

In the audio reproduction system of FIG. 14, by actually outputting the audio from the speaker 6L, the third term on the left side of the equations (11) and (12) of FIG. Transfer function FL up to 1L, 1R
By realizing L and FLR and actually outputting the sound from the speaker 6R, the third side on the left side of the equations (13) and (14) can be obtained.
From the speaker 6R, the left and right ears 1L and 1R of the listener 1
To realize the transfer functions FRL and FRR to reach the signal processing unit 3
By the correction processing of 0, the transfer function ratios of the first term and the second term on the left side of the equations (11) to (14) are realized.

Therefore, the transfer function from the sound source 5L to the left and right ears 1L and 1R of the listener 1 is controlled by the system on the side of the speaker 6L including the transfer functions FLL and FLR from the speaker 6L to the left and right ears 1L and 1R of the listener 1. HLL, HLR
Is realized and the left and right ears 1 of the listener 1 from the speaker 6R are realized.
The transfer functions HRL, HRR from the sound source 5R to the left and right ears 1L, 1R of the listener 1 are realized by the system on the speaker 6R side including the transfer functions FRL, FRR reaching L, 1R, and the left and right input audio signals Al ( Dl) and Ar (D
The sound image by r) can be localized at the positions of the sound sources 5L and 5R.

Specifically, in the signal processing section 30, the input digital audio signal Dl from the A / D converter 21 is supplied to the correction circuits 31a and 32a, and the A / D converter 2 is supplied.
The input digital audio signal Dr from 3 is corrected by the correction circuit 33a.
And 34a, and the adder circuit 35a supplies the correction circuit 3
The output signals of 1a and 33a are added, and the addition circuit 36a is added.
Then, add the output signals of the correction circuits 32a and 34a,
The output signal of the adder circuit 35a is supplied to the correction circuits 31b and 3b.
2b, the output signal of the addition circuit 36a is supplied to the correction circuits 33b and 34b, the addition circuit 35b adds the output signals of the correction circuits 31b and 33b, and the addition circuit 36b outputs the output signals of the correction circuits 32b and 34b. The output signals are added and the digital audio signals output from the adding circuits 35b and 36b are supplied to the D / A converters 41L and 41R as the audio signals SL and SR for driving the speakers 6L and 6R.

In this embodiment, a digital filter for obtaining long impulse response data is not required, and the circuit scale and the amount of calculation of the signal processing for sound image localization can be significantly reduced.

[0087]

As described above, according to the present invention, the circuit scale and the amount of calculation of the signal processing for sound image localization can be reduced, and the sound image can be localized with a sufficient sense of distance.

[Brief description of drawings]

FIG. 1 is a diagram showing a principle of a first embodiment.

FIG. 2 is a diagram showing an audio reproduction system according to a first embodiment.

FIG. 3 is a diagram showing an example of an impulse response.

FIG. 4 is a diagram showing an example of a digital filter.

FIG. 5 is a diagram showing a first example of a correction circuit.

FIG. 6 is a diagram showing a second example of a correction circuit.

FIG. 7 is a diagram showing a third example of a correction circuit.

FIG. 8 is a diagram showing an example of a frequency characteristic correction circuit.

FIG. 9 is a diagram showing a fourth example of a correction circuit.

FIG. 10 is a diagram showing an audio reproducing system according to a second embodiment.

FIG. 11 is a diagram showing an audio reproduction system according to a third embodiment.

FIG. 12 is a diagram showing an audio reproducing system according to a fourth embodiment.

FIG. 13 is a diagram showing the principle of the fourth embodiment.

FIG. 14 is a diagram showing an audio reproducing system according to a fifth embodiment.

FIG. 15 is a diagram showing the principle of the fifth embodiment.

FIG. 16 is a diagram showing the principle of a conventional method.

FIG. 17 is a diagram showing an example of a conventional audio reproduction system.

FIG. 18 is a diagram showing an example of an impulse response.

19 is a diagram showing an example of the digital filter of FIG.

20 is a diagram showing another example of the digital filter of FIG.

FIG. 21 is a diagram showing another example of a conventional audio reproduction system.

FIG. 22 is a diagram showing the principle of a conventional method for speaker reproduction.

FIG. 23 is a diagram showing an example of a conventional audio reproduction system in the case of speaker reproduction.

FIG. 24 is a diagram showing an example of the digital filter of FIG. 23.

FIG. 25 is a diagram showing another example of the digital filter of FIG. 23.

[Explanation of symbols]

Since the main parts are all described in the figure, they are omitted here.

Claims (23)

[Claims] 1. An input audio signal is corrected according to the difference between the transfer function from the sound image position to be localized to the left ear of the listener and the transfer function from the set sound image position to the left ear of the listener. , For the reproduction of the transfer function from the set sound image position to the left ear of the listener, while performing filtering processing, the input audio signal, the transfer function from the sound image position to be localized to the right ear of the listener, and the setting A sound signal to be filtered for reproduction of the transfer function from the set sound image position to the right ear of the listener after correction processing according to the difference from the transfer function from the set sound image position to the right ear of the listener. Processing method. 2. A transfer function from the sound image position to be localized to the left ear of the listener after filtering the input audio signal for reproduction of the transfer function from the set sound image position to the left ear of the listener, and Depending on the difference from the transfer function from the set sound image position to the listener's left ear, correction processing is performed, and the input audio signal is reproduced for the transfer function from the set sound image position to the listener's right ear. In accordance with the difference between the transfer function from the sound image position to be localized to the right ear of the listener and the transfer function from the set sound image position to the right ear of the listener after the filtering process, the audio signal to be corrected. Processing method. 3. A difference between a transfer function from the sound image position for localizing the first and second input audio signals to the left ear of the listener and a transfer function from the set sound image position to the left ear of the listener. According to the above, after correction processing, addition is performed, filtering processing is performed for reproduction of a transfer function from the set sound image position to the left ear of the listener, and the first and second input audio signals are Respectively, depending on the difference between the transfer function from the sound image position to be localized to the right ear of the listener, and the transfer function from the set sound image position to the right ear of the listener, after correction processing, add,
An audio signal processing method for performing a filtering process for reproducing a transfer function from the set sound image position to the right ear of a listener. 4. The audio signal processing method according to claim 3, wherein the set sound image position is a position on the median plane common to the first and second input audio signals. 5. The audio signal processing method according to claim 3, wherein the set sound image position is a position symmetrical with respect to the median plane with respect to the first and second input audio signals. Method. 6. The audio signal processing method according to claim 3 is executed for the first and second input audio signals in the first set, with the set sound image position as a position in the front half surface of the listener. An audio signal processing method for executing the audio signal processing method according to claim 3 on the first and second input audio signals in the second set, with the set sound image position as a position in the rear half surface of the listener. 7. A transfer function from a first sound image position, which is a sound image position to be localized with respect to a first input audio signal, to one ear of a listener, and a sound image position to be localized with respect to a second input audio signal. The first input audio signal is corrected according to the difference from the transfer function from the sound image position to the one ear and the transfer function from the second sound image position to the other ear of the listener; The second input audio signal is corrected according to the difference from the transfer function from the sound image position of 1 to the other ear, and the first input audio signal before the correction processing and the second input after the correction processing. A sound signal is added, and filtering processing is performed for reproduction of a transfer function from the first sound image position to the other ear, and a second input sound signal before correction processing and a first input after correction processing are performed. The audio signals are added, and from the second sound image position, the For reproduction of a transfer function leading to square ear, the audio signal processing method for filtering. 8. An input audio signal is corrected and supplied to the speaker according to a difference between a transfer function from a sound image position to be localized to a listener's ear and a transfer function from a speaker to a listener's ear. Audio signal processing method for obtaining an output audio signal. 9. The audio signal processing method according to claim 1, wherein the correction process is a process of delaying an input audio signal. 10. The audio signal processing method according to claim 1, wherein the correction processing delays an input audio signal, and
An audio signal processing method for correcting the level. 11. The audio signal processing method according to claim 1, wherein the correction processing delays an input audio signal, and
An audio signal processing method for correcting the frequency characteristic. 12. A correction process for correcting an input audio signal according to a difference between a transfer function from a sound image position to be localized to a left ear of a listener and a transfer function from a set sound image position to a left ear of the listener. Means for filtering the audio signal output from the correcting means for reproducing the transfer function from the set sound image position to the left ear of the listener, and the sound image for localizing the input audio signal. Correcting means for performing correction processing according to the difference between the transfer function from the position to the right ear of the listener and the transfer function from the set sound image position to the right ear of the listener, and an audio signal output from the correcting means. A voice reproduction system comprising: filtering means for performing a filtering process for reproducing the transfer function from the set sound image position to the right ear of the listener. 13. Filtering means for subjecting an input audio signal to reproduction of a transfer function from a set sound image position to a left ear of a listener, and a sound image position for localizing an audio signal output from the filtering means. From the transfer function from the listener to the left ear of the listener and the transfer function from the set sound image position to the listener's left ear, correction means for performing correction processing, and the input audio signal is set to the In order to reproduce the transfer function from the sound image position to the right ear of the listener, filtering means for performing a filtering process, and the audio signal of the output of this filtering means, the transfer function from the sound image position to be localized to the right ear of the listener, A sound reproduction system including a correction unit that performs correction processing according to a difference from a transfer function from the set sound image position to the right ear of the listener. Mu. 14. A difference between a transfer function from the sound image position where the first and second input audio signals are localized to the left ear of the listener and a transfer function from the set sound image position to the left ear of the listener. The first and second correction processing according to
And the audio signals output from the first and second correcting means are added to perform a filtering process for reproducing the transfer function from the set sound image position to the left ear of the listener. Filtering means, a transfer function from the sound image position for localization to the right ear of the listener, and a transfer function from the set sound image position to the right ear of the listener for the first and second input audio signals, respectively. Correction processing according to the difference between
Correction means and the audio signals output from the third and fourth correction means are added, and a second filtering process is performed in order to reproduce the transfer function from the set sound image position to the right ear of the listener. A sound reproduction system comprising: a filtering means. 15. The audio reproduction system according to claim 14, wherein the set sound image position is a position on the median plane common to the first and second input audio signals. 16. The audio reproduction system according to claim 14, wherein the set sound image position is a position that is symmetric with respect to the median plane and is separate for the first and second input audio signals. 17. A transfer function from the sound image position for localizing the first and second input audio signals in the first set to the left ear of the listener, and the listener from the sound image position set in the front half surface of the listener. The first set of first and second correction means for correction processing and the audio signals output from the first and second correction means of the first set according to the difference from the transfer function reaching the left ear of In addition, a first set of first filtering means for performing a filtering process for reproducing a transfer function from the sound image position set in the front half surface of the listener to the left ear of the listener, and a first set of the first set of the first set. A transfer function from the sound image position to be localized to the right ear of the listener and a transfer function from the sound image position set in the front half surface of the listener to the right ear of the listener for the first and second input audio signals, respectively. Depending on the difference
The sound image set in the front half surface of the listener is obtained by adding the sound signals output from the first and third correction means of the first set and the third and fourth correction means of the first set. In order to reproduce the transfer function from the position to the right ear of the listener, the first set of second filtering means for performing the filtering process and the sound image for localizing the first and second input audio signals in the second set, respectively. The second set of first and second sets to be corrected according to the difference between the transfer function from the position to the left ear of the listener and the transfer function from the sound image position set in the rear half surface of the listener to the left ear of the listener. Of the transfer function from the sound image position set in the rear half surface of the listener to the left ear of the listener by adding the audio signals of the outputs of the first and second correcting means of the second set. A second set of filtering processes for 1 filtering means, a transfer function from the sound image position for localizing the first and second input audio signals in the second set to the right ear of the listener, and a rear half surface of the listener. Depending on the difference from the transfer function from the sound image position to the listener's right ear,
A sound image set in the rear half surface of the listener by adding the sound signals output from the second and third correction means of the second set to be corrected and the output of the third and fourth correction means of the second set. A sound reproduction system comprising: a second set of second filtering means for performing a filtering process for reproducing the transfer function from the position to the right ear of the listener. 18. A transfer function from a first sound image position, which is a sound image position to be localized for a first input audio signal, to one ear of a listener, and a second sound image position, to be localized for a second input audio signal. First correction means for correcting the first input audio signal according to the difference from the transfer function from the sound image position to the one ear, and from the second sound image position to the other ear of the listener. Second correction means for correcting the second input audio signal according to the difference between the transfer function and the transfer function from the first sound image position to the other ear, and the first correction means before correction processing. First filtering means for performing a filtering process for adding the input audio signal and the second input audio signal after the correction process to reproduce a transfer function from the first sound image position to the other ear; Complementary with the second input audio signal before processing By adding the first input audio signal after processing, from said second sound image position for reproduction of the transfer function leading to the one ear, the sound reproduction system comprising a second filtering means for filtering, the. 19. An audio reproduction system comprising a correction means for correcting the input audio signal according to the difference between the transfer function from the sound image position to be localized to the listener's ear and the transfer function from the speaker to the listener's ear. . 20. The audio reproduction system according to claim 12, wherein the correction unit is a delay unit. 21. The audio reproduction system according to claim 12, wherein the correction unit includes a delay unit and a signal level correction unit. 22. The audio reproduction system according to claim 12, wherein the correction unit includes a delay unit and a frequency characteristic correction unit. 23. The audio reproduction system according to claim 12, wherein the correction means is an FIR filter.