JP2003230198A - Sound image localization control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a signal processing computation amount and to obtain a good sound image localization control effect in a sound image localization control device for reproducing, by a speaker or headphones set in another place, a sound characteristic replayed by a speaker set in a predetermined place. <P>SOLUTION: In a high-frequency band in which a head acoustic transfer function indicates a complicated characteristic, a characteristic of replay means is corrected to a characteristic of the head acoustic transfer function by finite- impulse response (FIR) type filter processing. In a low-frequency band in which the characteristic of the head acoustic transfer function can be represented by a level difference between both ears and a time difference between both ears, the characteristic of the replay means is corrected to the characteristic of the head acoustic transfer function by infinite-impulse response (IIR) type filter processing, gain setting, and delay processing. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound image localization control device for realizing out-of-head localization of acoustic signals.

[0002]

2. Description of the Related Art Conventionally, various methods have been proposed for localizing a sound image in a sound source direction in audio reproduction.

In sound image localization control using headphones, sound image localization control is performed using a head acoustic transfer function from an actual sound source such as a speaker to the dummy head and a transfer function of headphones mounted on the dummy head, using a dummy head or the like. The filter characteristics are calculated, and the acoustic signal is subjected to signal processing by using the filter characteristics as a coefficient of the digital filter. If sound image localization control is performed using a finite impulse response type filter (hereinafter referred to as FIR filter), the number of taps of the FIR filter increases and the amount of signal processing calculation becomes enormous, so the frequency characteristic is adjusted with a small number of taps. There is proposed a sound image localization control device capable of suppressing the amount of signal processing calculation by performing sound image localization control by using an infinite impulse response type filter (hereinafter referred to as an IIR filter) and a FIR filter which can be used together.

A conventional sound image localization control device using headphones will be described below with reference to the drawings. Figure 21
FIG. 1 is a diagram showing a basic configuration of a stereophonic sound processing device disclosed in Japanese Patent Laid-Open No. 9-84199. In FIG. 21, 1
a, 1b are delay units, 2a, 2b are amplifiers for controlling gain, 3a, 3b are IIR filters for adding target characteristics, that is, frequency characteristics of a head acoustic transfer function for a target sound source, 4a, 4b are headphones. F to remove acoustic characteristics
The IR filters 5 are filter coefficient selecting means for selecting and setting the filter coefficient used for control and the delay and gain based on the inputted listener position information.

The operation of the apparatus shown in FIG. 21 will be described below. In the delay units 1a and 1b, the filter coefficient selecting means 5 has a coefficient representing the binaural time difference of the impulse response of the target characteristic.
Is preset by the filter coefficient selecting means 5 in the amplifiers 2a and 2b, which represents the binaural level difference of the impulse response of the target characteristic, and in the IIR filters 3a and 3b, the frequency characteristic of the target characteristic is set. Is expressed in advance by the filter coefficient selecting means 5, and in the FIR filters 4a and 4b, a coefficient expressing the inverse characteristic of the impulse response of headphones (not shown) that is the output means is set in advance by the filter coefficient selecting means 5. ing.

The input signal is subjected to signal processing by the delay units 1a and 1b, the IIR filters 3a and 3b, and the amplifiers 2a and 2b, and the time characteristic and the frequency characteristic of the head acoustic transfer function H which is the target characteristic are corrected. The outputs of the amplifiers 2a and 2b are subjected to signal processing by the FIR filters 4a and 4b, so that the inverse characteristic 1 / C of the acoustic characteristic C of the headphones is corrected.
Therefore, when the outputs of the FIR filters 4a and 4b are heard through the headphones, the listener can feel as if he or she is listening to the sound from the target sound source.

The IIR filters 3a and 3b can suppress the amount of signal processing calculation to about 10 taps as compared with the case where the characteristics of the head acoustic transfer function are corrected by FIR filtering, but the head acoustic transfer function is complicated. The control accuracy is lowered in a high frequency band exhibiting various characteristics, and it becomes difficult to provide a listener with good sound image localization. Further, since the inverse characteristic of the sound reproducing means is corrected by using the FIR filters 4a and 4b over the entire frequency band, it is difficult to reduce the number of filter taps while maintaining the correction accuracy in the low frequency range.

[0008]

In view of the above-mentioned problems, the present invention reduces the amount of signal processing calculation for sound image localization control,
Moreover, it is intended to provide a listener with accurate sound image localization over the entire frequency band.

[0009]

A sound image localization control apparatus of the present invention includes a first infinite impulse response type filter for inputting an acoustic signal and performing sound image localization control in a low frequency band;
Finite impulse response type filter that inputs the output signal of the infinite impulse response type filter of No. 1 and performs the sound image localization control of the high frequency band, and the second finite impulse response type filter that inputs the acoustic signal and performs the sound image localization control of the low frequency band Response type filter, second finite impulse response type filter for inputting output signal of the second infinite impulse response type filter and performing sound image localization control in a high frequency band, and output of the first finite impulse response type filter And a sound reproducing means for reproducing an output signal of the second finite impulse response type filter.

The sound image localization control apparatus of the present invention further comprises a first infinite impulse response type filter for inputting an acoustic signal,
A first gain setting device for inputting an output signal of the first infinite impulse response filter; a first delay device for inputting an output signal of the first gain setting device; and a first delay device of the first delay device. A first finite impulse response filter for inputting an output signal, a second infinite impulse response filter for inputting an acoustic signal, and a second gain setting for inputting an output signal of the second infinite impulse response filter. , A second delay unit for inputting the output signal of the second gain setting unit, a second finite impulse response filter for inputting the output signal of the second delay unit, and the first finite unit A sound image localization control device comprising an output signal of an impulse response type filter and a sound reproducing means for reproducing an output signal of the second finite impulse response type filter, the first infinite impulse response type device Filter a first gain setting unit and the first
Delay device, the second infinite impulse response type filter, the second gain setting device and the second delay device perform sound image localization control in a low frequency band of an acoustic signal, and the first finite impulse response type filter The second finite impulse response filter is characterized by performing sound image localization control in a high frequency band of an acoustic signal.

In the sound image localization control apparatus of the present invention, an infinite impulse response type filter for inputting an acoustic signal and an output signal of the infinite impulse response type filter are input.
A delay unit, a first gain setting unit for inputting an output signal of the first delay unit, and a first finite impulse response type filter for inputting an output signal of the first gain setting unit,
A second gain setting device that inputs the output signal of the first delay device, a second delay device that inputs the output signal of the second gain setting device, and an output signal of the second delay device Sound image localization control including a second finite impulse response type filter for inputting, an output signal of the first finite impulse response type filter, and sound reproduction means for reproducing the output signal of the second finite impulse response type filter In the device, the infinite impulse response filter, the first gain setting device, the first delay device, the second gain setting device, and the second delay device perform sound image localization control in a low frequency band of an acoustic signal. The first finite impulse response type filter and the second finite impulse response type filter perform sound image localization control in a high frequency band of an acoustic signal.

Further, the sound image localization control apparatus of the present invention comprises a low-pass filter for extracting a low frequency band signal from an acoustic signal, a first infinite impulse response type filter for inputting an output signal of the low-pass filter, and the first A first gain setting device that inputs the output signal of the infinite impulse response type filter, a first delay device that inputs the output signal of the first gain setting device, and a second input device that inputs the output signal of the low-pass filter. Infinite impulse response type filter, a second gain setting device for inputting an output signal of the second infinite impulse response type filter, and a second delay device for inputting an output signal of the second gain setting device. A high-pass filter for extracting a high frequency band signal from an acoustic signal, and a first finite impulse response type filter for inputting an output signal of the high-pass filter A second finite impulse response type filter for receiving the output signal of said high-pass filter,
A first adder for adding the output signal of the first delay unit and the output signal of the first finite impulse response type filter, the output signal of the second delay unit and the second finite impulse response type A sound image localization control device comprising: a second adder for adding output signals of a filter; and sound reproduction means for reproducing an output signal of the first adder and an output signal of the second adder. , The first infinite impulse response filter, the first gain setting device, the first delay device, and the second
Of the infinite impulse response type filter, the second gain setting device and the second delay device perform sound image localization control in a low frequency band of an acoustic signal, and the first finite impulse response type filter and the second finite impulse response type The type filter is characterized by performing sound image localization control in a high frequency band of an acoustic signal.

The sound image localization control apparatus of the present invention includes a low-pass filter for extracting a low frequency band signal from an acoustic signal, an infinite impulse response type filter for inputting an output signal of the low pass filter, and an infinite impulse response type filter. A first delay unit for inputting an output signal, a first gain setting unit for inputting an output signal of the first delay unit, and a second delay unit for inputting an output signal of the first delay unit A second gain setting device for inputting an output signal of the second delay device, a high-pass filter for extracting a high frequency band signal from an acoustic signal, and a first finite impulse response for inputting an output signal of the high-pass filter Type filter,
A second finite impulse response filter for inputting the output signal of the high-pass filter, a first finite impulse response filter for adding the output signal of the first gain setting device, and an output signal of the output signal of the first finite impulse response filter. Adder, a second adder for adding the output signal of the second gain setting device and the output signal of the output signal of the second finite impulse response filter, and the output signal of the first adder And the second
Sound localization controller for reproducing the output signal of the adder of the above, the infinite impulse response type filter, the first gain setting device, the first delay device, and the second gain setting device. And the second delay device perform sound image localization control in the low frequency band of the acoustic signal, and the first finite impulse response type filter and the second finite impulse response type filter perform sound image localization control in the high frequency band of the acoustic signal. It is characterized by performing.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 1 to 20.

(First Embodiment) FIG. 1 shows a sound image localization control apparatus for a front L-channel sound source according to a first embodiment. 5
Reference numerals a and 5b are IIR filters, 6a and 6b are FIR filters, 7a and 7b are headphone reproducing units, and 8 is a listener wearing headphones. The input front L channel acoustic signal is transmitted to the IIR filters 5a and 5b and the FI.
The signals are processed by the R filters 6a and 6b and then input to the headphone reproducing units 7a and 7b. The listener 8 listens to the output signals of the reproduction units 7a and 7b. In the IIR filters 5a and 5b, coefficients calculated in advance so as to perform sound image localization control in the low frequency band are set.
The FIR filters 6a and 6b are set with coefficients calculated in advance so as to perform sound image localization control in the high frequency band.

FIG. 2 is a diagram showing the result of sound image localization control of the front L channel signal. Playback units 7a, 7
When the listener 8 hears the reproduced sound from b, the listener can feel that the sound is being reproduced from the front L speaker 9.

Next, a method of calculating the coefficient will be described. FIG. 3 shows an apparatus for measuring a head acoustic transfer function which is a target of sound image localization. The speaker 9 is located on the left 3 from the front of the dummy head 12.
Install in the direction of 0 degree. The measurement signal generator 10 reproduces the measurement signal from the speaker 9, which is an actual sound source. A microphone 13 that reproduces this reproduced sound in the ear canal of the dummy head 12
It is detected by a and 13b. The transfer function measuring device 11 uses the measurement signal from the measurement signal generator 10 and the microphone detection signal to measure the head acoustic transfer function Hl from the speaker 9 to the microphone 13a and the speaker 9 to the microphone 13b.
The head acoustic transfer function Hr up to is measured.

FIG. 4 shows an apparatus for measuring the transfer function of a reproducing unit attached to headphones. The headphones are correctly mounted on the dummy head 12, and the measurement signal from the measurement signal generator 10 is reproduced from the reproduction units 7a and 7b. The reproduced sound is detected by the microphones 13a and 13b installed in the ear canal of the dummy head 12. The transfer function measuring device 11 measures the transfer function Cl of the reproducing unit 7a and the transfer function Cr of the reproducing unit 7b using the measurement signal from the measurement signal generator 10 and the microphone detection signal.

Assuming that the transfer functions realized by the sound image localization control are Xl and Xr, respectively, it is sufficient that Hl and Hr can be reproduced at the ears of the dummy head 12, so that Hl = Xl.Cl Hr = Xr.Cr. Therefore, the transfer function of Xl = Hl / Cl Xr = Hr / Cr may be realized by the sound image localization control.

FIG. 5 is a diagram showing the amplitude frequency characteristics of the head acoustic transfer functions Hl and Hr. In the frequency band higher than about 1 kHz, both Hl and Hr have complex characteristics, but in the frequency band of 1 kHz or less, both Hl and Hr have monotonous characteristics. FIG. 6 shows the head acoustic transfer functions Hl and H.
It is a figure which shows the impulse response of r. It can be seen that the sound from the sound source requires time Δt0 to reach the left ear and time Δt0 + Δt to reach the right ear. Figure 5,
From the characteristics of FIG. 6, it is understood that the head acoustic transfer function can be accurately corrected by the binaural level difference α and the binaural time difference Δt in the low frequency band.

FIG. 7 is a diagram showing the amplitude frequency characteristics of the acoustic characteristics Cl and Cr of the headphones. The acoustic characteristics Cl and Cr of the headphones show monotonous characteristics in the wave number band of 1 kHz or less. From these results, the sound image localization control in the low frequency band may use the IIR filter with a small number of taps, and the sound image localization control in the high frequency band may use the FIR filter.

FIG. 8 is a diagram showing the configuration of the IIR filters 5a and 5b. 25a to 25g are gain setting devices, 26a
26f are adders, and 27a and 27b are delay devices. The input signal is branched into a signal input to the delay device 27a and a signal input to the gain setting device 25a, and the delay device 27a
The signal processed by a is the signal input to the delay device 27b, the signal processed by the gain setting device 25b, and the gain setting device 2.
It is branched to the signal processed by 5e. This series of signal processings are connected and processed a plurality of times, the output signal of the gain setting device is added by an adder, and then the input signal and the gain setting device 25 are input.
Add to the output of a. The delay devices 27a and 27b perform delay processing of unit samples. Further, when the above signal processing is performed by connecting n times, the filter coefficients, that is, the coefficients set in the gain setters 25a to 25g are b0 and b, respectively.
1, b2, bn, c1, c2, cn, and the characteristics of the output signal can be adjusted by changing the values of these coefficients.

The filter coefficients of the IIR filters 5a and 5b represent the frequency characteristics of 1 / Cl and 1 / Cr, which are the inverse characteristics of the acoustic characteristics Cl and Cr of the headphones in the frequency band of 1 kHz or less, and represent the frequency band higher than 1 kHz. Then, the coefficient is calculated so as to express a flat frequency characteristic. Further, adjustment to the binaural level difference α, which is a characteristic of the low frequency band of the head acoustic transfer function, is applied to this coefficient, and b0, b1, b2, ...
It is given to c1, c2, ..., cn. In a FIR filter that performs sound image localization control in a high frequency band, the binaural time difference Δ
Since t is expressed, the binaural time difference expressing the characteristics of the low frequency band of the head acoustic transfer function is not expressed by the IIR filter.

FIG. 9 is a diagram showing the configuration of the FIR filters 6a and 6b. 25a to 25d are gain setting devices, 26a
26c are adders, and 27a and 27b are delay devices. The input signal is branched and input to the gain setters 25a to 25d. When there are n + 1 gain setters, the output signal of the gain setter 25d undergoes delay processing n times before being input to the adder 26a. Delay devices 27a and 27b
In, the delay processing of the unit sample is performed. The filter coefficients, that is, the coefficients set in the gain setters 25a to 25d are a0, an-2, an-1, and an, respectively.
The characteristics of the output signal can be adjusted by changing the values of these coefficients.

The filter coefficients of the FIR filters 6a and 6b give coefficients so as to express a flat frequency characteristic in the low frequency band and an amplitude frequency characteristic of the transfer functions Xl and Xr in the high frequency band. Binaural time difference Δ
t is corrected to adjust the coefficient, and the correction for the binaural level difference α is performed so that the output of the FIR filter 6a becomes smaller than the output of the FIR filter 6b by the level α, and the filter coefficient is a0, ... , An-2, an-1,
give to an.

In the above description, the front L channel signal is taken as an example, but even in the case of other multi-channel signals,
It can be realized by the same idea.

Further, the sound image localization control of the multi-channel signal can be performed by simultaneously performing the same signal processing on the multi-channel signal of the DVD or the like. FIG. 10 shows D
This is a sound image localization control device for 6-channel digital signals input from a VD player. Reference numerals 5a to 5j are IIR filters that perform low-frequency sound image localization control, 6a to 6j are FIR filters that perform high-frequency sound image localization control, 7a and 7b are reproduction units attached to headphones, 8 is a listener wearing headphones, 14 Is a delay device, and 15a to 15h are adders.

Sound image localization control means for the center channel signal, the front R channel signal, the surround L channel signal, and the surround R channel signal are arranged in parallel,
A delay device for delaying the woofer channel signal is added, and an adder for adding the five channel signals subjected to sound image localization control and the delayed woofer channel signal is added. Since the operation of the sound image localization control of the center channel signal, the front R channel signal, the surround L channel signal, and the surround R channel signal has already been described, the delay processing of the woofer channel signal and the addition of each sound image localization controlled channel signal will be described. .

The input woofer channel signal is
Output without sound image localization control. Adder 15d and adder 1
When adding with other channel signals whose sound image localization is controlled in 5h, in order to synchronize the signals, the other channel signals are delayed by the time required for signal processing for sound image localization control in order to synchronize the signals. There must be. Therefore, the time required for signal processing for controlling the sound image localization of the other channel signal is set in the delay device 14. The delay-processed woofer channel signals and the respective sound-image-localized channel signals are added to the adders 15a to 15a.
At 5h, they are added together and output from the playback units 7a and 7b of the headphones.

The input woofer channel signal is not subjected to sound image localization control, but the input woofer channel signal is added before the other channel signals are subjected to sound image localization control, that is, before being processed by the IIR filters 5a to 5j. It is also possible to perform sound image localization control on the woofer channel signal by adding to.

Next, a description will be given of the case where a signal subjected to sound image localization control is reproduced using two speakers. FIG. 11 shows
It is a sound image localization control device for a front L channel sound source when two speakers are used as reproducing means. Reference numerals 5a and 5b are IIR filters that perform low-frequency sound image localization control, 6a and 6b are FIR filters that perform high-frequency sound image localization control, 8 is a listener, 1
6a and 16b are crosstalk cancel circuits, 17a and
Reference numeral 17b is a speaker for reproducing a signal subjected to sound image localization control via an amplifier (not shown), and 18a and 18b are subtractors. Instead of headphones, speakers 17a and 17b are used as reproduction means, and crosstalk cancel circuits 16a and 16b are used.
b and subtractors 18a and 18b are added. II
Since the sound image localization control using the R filters 5a and 5b and the FIR filters 6a and 6b has been already described, the transfer function X of the crosstalk cancel circuits 16a and 16b is described.
The setting of 1 and X2 will be described.

By subtracting the output signal of the crosstalk cancel circuit 16a from the output signal of the FIR filter 6b, the crosstalk transfer function S from the right speaker 17b to the left ear is obtained.
By canceling rl and subtracting the output signal of the crosstalk cancel circuit 16b from the output signal of the FIR filter 6a, the crosstalk transfer function Slr of the left speaker 17a to the right ear is canceled. Crosstalk transfer function Sr of the left ear
1 and the crosstalk transfer function Slr of the right ear to the head acoustic transfer functions Hl and Hr to the left and right ears of the front L channel.
When expressed by using, Sll (Hl−Hr · X2) + Srl (Hr−Hl · X1) = Hl Srr (Hr−Hl · X1) + Slr (Hl−Hr · X2) = Hr holds.

By obtaining X1 and X2 that satisfy the simultaneous equations, the reproduction of the front L speaker by the speakers 17a and 17b can be realized. That is, X1 = (Hl.Srr-Hr.Sll + Hr.Sll.Srr-Hr.Srl.Srr) / Hl (Sll.Srr-Srl.Slr) X2 = (Hr.Srl) in the crosstalk cancel circuits 16a and 16b. It suffices to give a transfer function of −Hl · Srr + Hl · Sll · Srr−Hl · Srl · Slr) / Hr (Sll · Srr−Srl · Slr).

As described above, the low frequency band characteristic of the head acoustic transfer function is approximated by the binaural level difference and the binaural time difference, the correction is realized by the IIR filter, and the head acoustic transfer function shows a complicated characteristic. In the high frequency band, since the correction is performed by the FIR filter, the control accuracy can be improved.

Further, since the characteristic correction of the sound reproducing means is performed by the IIR filter in the low frequency band and the FIR filter in the high frequency band, the load of the signal processing can be reduced.

Before being processed by the IIR filter in order to express the difference between the inclination of the characteristics of the head acoustic transfer function represented by ΔHl / Δf in the low frequency band and the inclination of both ears in the case of the left ear. In addition, another IIR filter may be added to give a coefficient for correcting the inclination of the target characteristic in the low frequency band to perform more accurate sound image localization control.

The transfer function low frequency band characteristic of the reproducing unit of the headphones may be corrected by analog filter processing.

In the case of controlling the sound image localization of the center channel sound source, it is assumed that the head acoustic transfer functions are substantially equal in the left and right ears, and two IIR filters of the configuration of FIG. 1 are used together, or two IIR filters are used. It is also possible to employ a configuration in which a filter and an FIR filter are used together.

(Second Embodiment) FIG. 12 shows a sound image localization control apparatus for a front L channel sound source according to a second embodiment.
Reference numerals 5a and 5b are IIR filters, 6a and 6b are FIR filters, 7a and 7b are headphone reproducing units, 8 is a listener wearing headphones, 19a and 19b are gain setting devices, and 20a and 20b are delay devices.

The input front L-channel acoustic signal has IIR filters 5a and 5b and a gain setter 19a.
19b and delay device 20a, 20b and FIR filter 6a,
Headphone playback unit 7 after signal processing at 6b
It is input to a and 7b. The listener 8 is the reproduction unit 7a,
Listen to the output signal of 7b. IIR filters 5a and 5b
And gain setting devices 19a and 19b and delay devices 20a and 20b
Is set to a coefficient calculated in advance so as to perform sound image localization control in the low frequency band. In the FIR filters 6a and 6b, coefficients calculated in advance so as to perform sound image localization control in a high frequency band are set. As in the case of the first embodiment, when the listener 8 hears the reproduced sound from the reproduction units 7a and 7b, the listener can feel that the sound is being reproduced from the front L speaker 9.

Next, the IIR filters 5a and 5b, the gain setters 19a and 19b, the delay devices 20a and 20b, and the FIR.
A method of calculating the coefficients of the filters 6a and 6b will be described. The IIR filters 5a and 5b are used to correct the transfer function low frequency band characteristic of the headphone reproducing units 7a and 7b, which is a reproducing means in the sound image localization control for the low frequency band, and the inverse characteristic 1 of the acoustic characteristic of the headphone in the low frequency band. For the frequency characteristics of / Cl and 1 / Cr, a coefficient calculated in advance is set so as to express a flat frequency characteristic in the high frequency band. Gain setters 19a and 19b and delay device 2
0a and 20b set a coefficient calculated in advance so as to correct the binaural level difference α and the binaural time difference Δt as the head acoustic transfer function low-frequency characteristic in the sound image localization control for the low frequency band. Δt0 is given as a coefficient to the delay device 20a, and Δt0 + Δt is given as a coefficient to the delay device 20b. The FIR filters 6a and 6b set coefficients calculated in advance so as to perform sound image localization control in the high frequency band. However, since the delay devices 20a to 20b represent the binaural time difference, the FIR filters 6a and 6b adjust the coefficients so that their impulse responses have no delay.

Although the front L channel signal has been described above as an example, even in the case of other multi-channel signals,
The idea is the same.

The sound image localization control of the multi-channel signal may be performed by simultaneously performing the same signal processing on the multi-channel signal.

Although the headphones are used as the means for reproducing the signal subjected to the sound image localization control, two speakers may be used as the reproducing means.

The headphone reproduction units 7a, 7
The correction of the transfer function low band characteristic of b may be realized by analog filter processing.

In the case of controlling the sound image localization of the center channel sound source, it is assumed that the left and right ears have substantially the same head acoustic transfer function, and two IIR filters in the configuration of FIG. A filter and a gain setting device are used together, or two IIR filters, a gain setting device and a delay device are used together, or two IIR filters, a gain setting device, a delay device and F are provided.
It is also possible to adopt a configuration in which IR filters are used together.

It should be noted that the headphone reproducing units 7a, 7
Although the correction of the transfer function low-frequency characteristic of b is performed separately by the left unit IIR filter 5a and the right unit IIR filter 5b, the left and right units are considered to be almost equal, and one IIR filter is used in combination. It is also possible to process.

As described above, the correction of the low frequency band of the head acoustic transfer function is performed by the gain setter and the delay device, the correction of the low frequency band of the sound reproduction means reverse characteristic is performed by the IIR filter, and the correction of the high frequency band is performed by the FIR filter. Therefore, the control accuracy can be improved.

(Third Embodiment) FIG. 13 shows a sound image localization control apparatus for a front L-channel sound source according to the third embodiment. Reference numerals 6a and 6b are FIR filters, 7a and 7b are headphone reproducing units, 8 is a listener wearing headphones, 19a and 19b are gain setting devices, 20a and 20b are delay devices, and 21 is an IIR filter. IIR filters 5a and 5b are deleted from the configuration of the second embodiment, an IIR filter 21 is added, and a gain setter 19a,
19b and the delay devices 20a and 20b are arranged at different positions.

The IIR filter 21 sets a coefficient for correcting the transfer function low-pass characteristic of the headphone reproducing units 7a and 7b, which is reproducing means, in the sound image localization control for the low frequency band. The delay devices 20a and 20b provide a coefficient to correct the binaural time difference. As a delay to the left ear, Δ
Give t0 as a coefficient. Since the delay to the right ear is expressed by the delay device 20a and the delay device 20b, the delay device 20a
b is given as a coefficient. Gain setters 19a, 1
A coefficient is given to 9b so as to correct the binaural level difference.

The front L channel signal has been described above as an example, but the concept is the same for other multi-channel signals in which the arrival of sound in the right ear is delayed as compared with that in the left ear.

FIG. 14 shows a sound image localization control device for a front R channel sound source. 6a and 6b are FIR filters, 7
a and 7b are headphone reproducing units, 8 is a listener wearing headphones, 19a and 19b are gain setting devices, 20
a and 20b are delay devices, and 21 is an IIR filter. With this configuration, it is possible to use a delay device that expresses the delay to the right ear. Since the basic sound image localization operation is the same as that of the configuration shown in FIG. 13, how to give the coefficients of the delay devices 20a and 20b will be described.

Regarding the delay to both ears, Hl and Hr in FIG.
Contrary to what was shown in the impulse response of, the delay to the left ear is Δ
If t0 + Δt and the delay to the right ear are represented by Δt0, Δt0 is given to the delay device 20a as a coefficient. Since the delay to the left ear is expressed by the delay device 20a and the delay device 20b, Δt is given to the delay device 20b as a coefficient. The same applies to the sound image localization control of other channels in which the arrival of sound in the left ear is delayed as compared with that in the right ear.

Two speakers may be used as the reproducing means instead of the headphones as the means for reproducing the sound image localization controlled signal.

Incidentally, the correction of the transfer function low-frequency characteristic of the reproducing unit of the headphones may be realized by analog filter processing.

Since one signal processing by the IIR filter is reduced, it is possible to reduce the signal processing calculation amount of the sound image localization control, and by partially sharing the delay processing for both ears, the capacity of the delay device, that is, Memory can be reduced.

(Fourth Embodiment) FIG. 15 shows a sound image localization control apparatus for a front L-channel sound source according to the fourth embodiment. 5a and 5b are IIR filters, 6a and 6b are FI
R filter, 7a and 7b are headphone reproducing unit, 8
Is a listener wearing headphones, 19a and 19b are gain setting devices, 20a and 20b are delay devices, 22 is a low-pass filter, 23 is a high-pass filter, and 24a and 24b are adders.

The input acoustic signal is processed by the low-pass filter 22 and the high-pass filter 23, and a low frequency band signal and a high frequency band signal are extracted.
The output of the low-pass filter 22 is a low-frequency band signal, and the IIR filters 5a and 5b and the gain setter 19a,
Signal processing is performed by 19b and the delay devices 20a and 20b. The output of the high pass filter 23 is a high frequency band signal,
The signals are processed by the FIR filters 6a and 6b.

The outputs of the delay devices 20a and 20b and the outputs of the FIR filters 6a and 6b are added by the adders 24a and 24b and input to the headphone reproducing units 7a and 7b. The listener 8 listens to the output signals of the reproduction units 7a and 7b.

The IIR filters 5a and 5b reverse the acoustic characteristics of the headphones in the low frequency band as a correction of the transfer function low range characteristics of the headphone reproducing units 7a and 7b which are reproducing means in the sound image localization control in the low frequency band. The coefficient calculated in advance is set so as to express the frequency characteristics of the characteristics 1 / Cl and 1 / Cr. Gain setters 19a, 1
The 9b and the delay devices 20a and 20b use a coefficient calculated in advance to correct the binaural level difference α and the binaural time difference Δt as the head acoustic transfer function low-frequency characteristic in the sound image localization control for the low frequency band. Set. FIR filter 6a,
6b sets a coefficient calculated in advance so as to perform sound image localization control in the high frequency band. Therefore, when the listener 8 listens to the reproduced sound from the reproduction units 7a and 7b, he / she can feel that the sound is reproduced from the front L speaker 9 as shown in FIG.

Next, how to give the coefficients will be described. The FIR filters 6a and 6b that perform high-frequency sound image localization control are provided with filter coefficients that represent the amplitude frequency characteristics of the transfer functions Xl and Xr described in the first embodiment in the high frequency band. The IIR filters 5a and 5b are provided with filter coefficients expressing the amplitude frequency characteristics in the low frequency band of the transfer functions 1 / Cl and 1 / Cr described in the first embodiment.
A coefficient is given to the gain setters 19a and 19b so as to express the binaural level difference α. However, at the boundary of the control frequency band (hereinafter referred to as the crossover frequency), the FIR
It is necessary to adjust so that the levels of the output signals of the filters 6a and 6b match. Therefore, FIG. 16 or FIG.
FIR filters 6a and 6b using the measuring device shown in
The frequency characteristics of signals processed by Hfir_l, H
The frequency characteristics Hgd_l and Hgd_r of the signals processed by the fir_r and IIR filters 5a and 5b, the gain setters 19a and 19b, and the delay devices 20a and 20b are measured.

FIG. 16 shows an apparatus for measuring the amplitude frequency characteristics of the output signals of the FIR filters 6a and 6b in the configuration of FIG. The measurement signal from the measurement signal generator 10 is processed by the high-pass filter 23 and the FIR filters 6a and 6b, and then reproduced by the reproduction units 7a and 7b. The reproduced sound is detected by the microphones 13a and 13b installed in the ear canal of the dummy head 12. The transfer function measuring device 11 uses the measurement signal from the measurement signal generator 10 and the microphone detection signal to measure the amplitude frequency characteristics Hfir_l and Hfir_r of the output signals of the FIR filters 6a and 6b.

FIG. 17 shows the delay device 2 in the configuration of FIG.
This is a device for measuring the amplitude frequency characteristics of the output signals of 0a and 20b. The measurement signal from the measurement signal generator 10 is processed by the low-pass filter 22, the IIR filters 5a and 5b, the gain setting devices 19a and 19b, and the delay devices 20a and 20b, and then reproduced by the reproduction units 7a and 7b. The reproduced sound is detected by the microphones 13a and 13b installed in the ear canal of the dummy head 12. Transfer function measuring instrument 11
Measures the amplitude frequency characteristics Hgd_l and Hgd_r of the output signals of the delay devices 20a and 20b using the measurement signal from the measurement signal generator 10 and the microphone detection signal.

FIG. 18 shows frequency characteristics Hfir_l and Hgd.
It is a figure which shows _l. The frequency characteristic Hfir_r has the same result as that of the frequency characteristic Hfir_l.
Since d_r has the same result as the frequency characteristic Hgd_r, it is not shown. In this figure, the transfer functions Hl / Cl and Hfir_l to be realized by the sound image localization control are shown so that the levels are the same in the high range. The level difference gl between Hfir_l and Hgd_l at the crossover frequency is given as a coefficient of the gain setter 19a. Similarly, the level difference between the frequency characteristics Hfir_r and Hgd_r is determined by the gain setter 1.
It is given as a coefficient of 9b.

A coefficient is given to the delay devices 20a and 20b so as to express the binaural time difference Δt. By the way, FI
Time TH required for signal processing of the R filters 6a and 6b,
IIR filters 5a and 5b and gain setters 19a and 19
b and the time TL required for signal processing of the delay devices 20a and 20b
There is a difference of. Further, in the FIR filter processing, a phase shift may occur between the input signal and the output signal depending on the filter coefficient. Considering the processing time difference TH-TL and the delay α for compensating for the phase shift, Δt0 + TH-TL + α is given to the delay device 20a as a coefficient, and the delay device 2
For 0b, Δt0 + Δt + TH-TL + α is given as a coefficient.

In the above description, the front L channel signal is taken as an example, but even in the case of other multi-channel signals,
Is the same.

Note that sound image localization control of a multi-channel signal is also possible by simultaneously performing the same signal processing on the multi-channel signal.

It should be noted that two speakers may be used as the reproducing means instead of the headphones as the means for reproducing the sound image localization controlled signal.

The headphone reproducing units 7a, 7
It is also possible to realize the correction of the transfer function low band characteristic of b by analog filter processing.

Incidentally, the headphone reproducing units 7a, 7
Although the correction of the transfer function low-frequency characteristic of b is performed separately by the left unit IIR filter 5a and the right unit IIR filter 5b, the left and right units are considered to be almost equal, and one IIR filter is used in combination. It is also possible to process.

If the control accuracy in the low frequency band is degraded but the signal processing calculation amount is further reduced, the IIR filters 5a and 5b may be omitted.

In the case of controlling the sound image of the center channel signal, it is possible to consider that the head acoustic transfer functions of the left ear and the right ear are almost the same, and perform processing by using one level setter together.

In the case of controlling the sound image of the center channel signal, it is considered that the head acoustic transfer functions of the left ear and the right ear are almost equal, and therefore, one level setting device and one delay device are used in combination for processing. Good.

In the case of controlling the sound image of the center channel signal, one FIR filter may be used in combination, considering that the head acoustic transfer functions of the left and right ears are substantially equal.

In the case of the left ear, the IIR filter 5a,
Add another IIR filter before processing in 5b
If a coefficient for correcting the inclination of the target characteristic in the low frequency band of the head acoustic transfer function represented by / Δf is given, more accurate sound image localization control can be realized.

The low-frequency correction of the head acoustic transfer function is performed by the gain setting device and the delay device, and the low-frequency correction of the sound reproducing means reverse characteristic is IIR.
Since the high frequency correction is performed by the filter using the FIR filter, the control accuracy can be improved.

(Fifth Embodiment) FIG. 19 shows a sound image localization control apparatus for a front R channel sound source in the fifth embodiment. 6a and 6b are FIR filters, 7a and 7b are headphone reproducing units, 8 is a listener wearing headphones, 19a and 19b are gain setting devices, 20a and 20b are delay devices, 21 is an IIR filter, 22 is a low pass filter, and 23. Is a high pass filter, and 24a and 24b are adders. II for the sound image localization control device of the fourth embodiment
The R filters 5a and 5b are deleted, the IIR filter 21 is added, and the gain setting devices 19a and 19b and the delay devices 20a and 2 are added.
The arrangement position of 0b is changed.

Here, the sound image localization control operation in the low frequency band will be described. The IIR filter 21 sets a coefficient for correcting the transfer function low-frequency characteristic of the headphone reproducing units 7a and 7b, which is reproducing means, in the sound image localization control for the low frequency band. The delay devices 20a and 20b give a coefficient to correct the binaural time difference. As a delay to the left ear, Δt0 + TH-TL + α is given to the delay device 20a as a coefficient. Since the delay to the right ear is expressed by the delay device 20a and the delay device 20b, Δt is given to the delay device 20b as a coefficient. The gain setters 19a and 19b are provided with coefficients in the same manner as described in the fourth embodiment so as to correct the binaural level difference.

The front L channel signal has been described above as an example, but the concept is the same for other multi-channel signals in which the arrival of sound in the right ear is delayed as compared with that in the left ear.

FIG. 20 shows a sound image localization control device for a front R channel sound source. 6a and 6b are FIR filters, 7
a and 7b are headphone reproducing units, 8 is a listener wearing headphones, 19a and 19b are gain setting devices, 20
a and 20b are delay devices, 21 is an IIR filter, 22 is a low pass filter, and 23 is a high pass filter. With this configuration, it is possible to use a delay device that expresses the delay to the right ear. Since the basic sound image localization operation is the same as that of the configuration shown in FIG. 19, how to give the coefficients of the delay devices 20a to 20b will be described.

Regarding the delay to both ears, Hl and Hr in FIG.
Contrary to what was shown in the impulse response of, the delay to the left ear is Δ
If t0 + Δt and the delay to the right ear are represented by Δt0, the delay unit 20a includes TH, TL, and TH described in the fourth embodiment.
Δt0 + TH-TL + α in which α is taken into consideration is given as a coefficient. Regarding the delay to the left ear, the delay device 20a and the delay device 2 are used.
Since it is represented by 0b, Δt is given to the delay device 20b as a coefficient. The same applies to the sound image localization control of other channels in which the arrival of sound in the left ear is delayed as compared with that in the right ear.

It should be noted that two speakers may be used as the reproducing means as the means for reproducing the signal subjected to the sound image localization control.

It should be noted that the headphone reproducing units 7a, 7
The correction of the transfer function low band characteristic of b may be realized by analog filter processing.

Since one signal processing by the IIR filter is reduced as compared with the configuration of the fourth embodiment, it is possible to reduce the signal processing calculation amount of the sound image localization control, and the delay processing for both ears is partially shared. By doing so, the capacity of the delay device, that is, the memory can be reduced.

[0085]

In the sound image localization control apparatus of the present invention described above, in the high frequency band where the head acoustic transfer function has a complicated characteristic, the characteristic of the reproducing means is changed to the head acoustic transfer function by the FIR filter processing. In the low frequency band where the characteristics of the head acoustic transfer function can be accurately represented by the level difference and the time difference of the sound in both ears, the characteristics of the reproducing means are set by the gain setting and delay processing of the input signal. Since the characteristics of the acoustic transfer function are corrected, the number of taps of the FIR filter used for sound image localization control can be reduced, and the amount of signal processing calculation can be reduced. Further, since the characteristics of the head acoustic transfer function in the low frequency band can be approximated with sufficient accuracy by the correction, a good sound image localization can be provided to the listener.

[Brief description of drawings]

FIG. 1 is a diagram showing a sound image localization control device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a result of sound image localization control of a front L channel signal according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an apparatus for measuring a target characteristic according to the first embodiment of the present invention.

FIG. 4 is a diagram showing an apparatus for measuring a transfer function of headphones according to the first embodiment of the present invention.

FIG. 5 is a diagram showing amplitude frequency characteristics of a head acoustic transfer function of a front L-channel sound source.

FIG. 6 is a diagram showing an impulse response of a head acoustic transfer function of a front L-channel sound source.

FIG. 7 is a diagram showing amplitude frequency characteristics of a transfer function of headphones according to the first embodiment of the present invention.

FIG. 8 is a diagram showing an IIR filter according to an embodiment of the present invention.

FIG. 9 is a diagram showing an FIR filter according to the first embodiment of the present invention.

FIG. 10 is a diagram showing a sound image localization control device for multi-channel signals according to the first embodiment of the present invention.

FIG. 11 is a diagram showing a sound image localization control device using the output means as a speaker in the first embodiment of the present invention.

FIG. 12 is a diagram showing a sound image localization control device according to a second embodiment of the present invention.

FIG. 13 is a diagram showing a sound image localization control device according to a third embodiment of the present invention.

FIG. 14 is a diagram showing a sound image localization control device for an input signal of a channel in which the arrival of sound in the left ear is delayed as compared with the right ear in the third embodiment of the present invention.

FIG. 15 is a diagram showing a sound image localization control device according to a fourth embodiment of the present invention.

FIG. 16 is a diagram showing an apparatus for measuring the amplitude frequency characteristic of the output signal of the FIR filter according to the fourth embodiment of the present invention.

FIG. 17 is a diagram showing an apparatus for measuring an amplitude frequency characteristic of a delay device output signal according to a fourth embodiment of the present invention.

FIG. 18 is a diagram showing amplitude frequency characteristics of a FIR filter output signal and a delayer output signal according to the fourth embodiment of the present invention.

FIG. 19 is a diagram showing a sound image localization control device according to a fifth embodiment of the present invention.

FIG. 20 is a diagram showing a sound image localization control device for an input signal of a channel in which the arrival of sound in the left ear is delayed as compared with that in the right ear in the fifth embodiment of the present invention.

FIG. 21 is a block diagram showing a conventional sound image localization control device.

[Explanation of symbols]

1a, 1b Delay unit 2a, 2b Amplifier 3a, 3b IIR filter 4a, 4b FIR filter 5 Filter coefficient selecting means 5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h, 5
i, 5j IIR filters 6a, 6b, 6c, 6d, 6e, 6f, 6g, 6h, 6
i, 6j FIR filters 7a, 7b Headphone reproducing unit 8 Listener 9 Speaker 10 Measurement signal generator 11 Transfer function measuring device 12 Dummy heads 13a, 13b Microphone 14 Delay devices 15a, 15b, 15c, 15d, 15e, 15f, 1
5h Adder 16a, 16b Crosstalk cancel circuit 17a, 17b Speaker 18a, 18b Subtractor 19a, 19b Gain setter 20a, 20b Delay device 21 IIR filter 22 Low pass filter 23 High pass filter 24a, 24b Adder 25a, 25b, 25c, 25d, 25e, 25f, 2
5g Gain setting device 26a, 26b, 26c, 26d, 26e, 26f Adder 27a, 27b Delay device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroyuki Hashimoto             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Isao Kakuhari             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Kazuto Abe             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 5D062 AA65 AA74 BB10

Claims (5)

[Claims] 1. A first infinite impulse response type filter for inputting an acoustic signal to control a sound image localization in a low frequency band, and an output signal of the first infinite impulse response type filter for inputting a sound image localization in a high frequency band. A first finite impulse response type filter for controlling, a second infinite impulse response type filter for performing sound image localization control of a low frequency band by inputting an acoustic signal, and an output signal of the second infinite impulse response type filter. A second finite impulse response type filter for inputting and performing sound image localization control in a high frequency band; an acoustic signal for reproducing the output signal of the first finite impulse response type filter and the output signal of the second finite impulse response type filter A sound image localization control device comprising a reproducing means. 2. A first infinite impulse response filter for inputting an acoustic signal, a first gain setting device for inputting an output signal of the first infinite impulse response filter, and the first gain setting device. A first delay device for inputting the output signal of the first delay device, a first finite impulse response type filter for inputting the output signal of the first delay device, and a second infinite impulse response type filter for inputting an acoustic signal, A second gain setting device for inputting an output signal of the second infinite impulse response type filter; a second delay device for inputting an output signal of the second gain setting device; and a second delay device of the second delay device. A second finite impulse response type filter for inputting an output signal, an acoustic signal for reproducing the output signal of the first finite impulse response type filter and the output signal of the second finite impulse response type filter A sound image localization control device comprising a live means, comprising: a first infinite impulse response type filter, a first gain setting device, a first delay device, a second infinite impulse response type filter, and a second infinite impulse response type filter. The gain setting device and the second delay device perform sound image localization control in the low frequency band of the acoustic signal, and
The finite impulse response type filter and the second finite impulse response type filter perform sound image localization control in a high frequency band of an acoustic signal. 3. An infinite impulse response type filter for inputting an acoustic signal, a first delay unit for inputting an output signal of the infinite impulse response type filter, and a first delay unit for inputting an output signal of the first delay unit. A gain setting device, a first finite impulse response filter for inputting an output signal of the first gain setting device, a second gain setting device for inputting an output signal of the first delay device, A second delay device for inputting the output signal of the second gain setting device; a second finite impulse response filter for inputting the output signal of the second delay device; and the first finite impulse response filter Of the infinite impulse response type filter and the first gain setting device, the sound image localization control device comprising: an output signal of the second finite impulse response type filter and a sound reproducing means for reproducing the output signal of the second finite impulse response type filter. The localizer, the first delay device, the second gain setting device, and the second delay device perform sound image localization control in the low frequency band of the acoustic signal,
The sound image localization control device, wherein the first finite impulse response filter and the second finite impulse response filter perform sound image localization control in a high frequency band of an acoustic signal. 4. A low pass filter for extracting a low frequency band signal from an acoustic signal, a first infinite impulse response type filter for inputting an output signal of the low pass filter, and an output signal of the first infinite impulse response type filter. A first gain setter for inputting the signal, a first delay unit for inputting the output signal of the first gain setting unit, a second infinite impulse response type filter for inputting the output signal of the low-pass filter, A second gain setting device for inputting an output signal of the second infinite impulse response filter, a second delay device for inputting an output signal of the second gain setting device, and a high frequency band signal from an acoustic signal Of the high-pass filter, a first finite impulse response type filter for inputting an output signal of the high-pass filter, A second finite impulse response filter for inputting a force signal; a first adder for adding the output signal of the first delay device and the output signal of the first finite impulse response filter; and the second Second adder for adding the output signal of the second delay unit and the output signal of the second finite impulse response type filter, and the output signal of the first adder and the output signal of the second adder A sound image localization control device comprising: a sound reproducing unit for reproducing the sound, the first infinite impulse response filter, the first gain setting device, the first delay device, the second infinite impulse response filter, and the second infinite impulse response filter. The second gain setting device and the second delay device perform sound image localization control in the low frequency band of the acoustic signal, and
The finite impulse response type filter and the second finite impulse response type filter perform sound image localization control in a high frequency band of an acoustic signal. 5. A low pass filter for extracting a low frequency band signal from an acoustic signal, an infinite impulse response type filter for inputting an output signal of the low pass filter, and a first input for inputting an output signal of the infinite impulse response type filter. A delay unit, a first gain setting unit that inputs the output signal of the first delay unit, a second delay unit that inputs the output signal of the first delay unit, and a second delay unit of the second delay unit A second gain setting device for inputting an output signal; a high-pass filter for extracting a high frequency band signal from an acoustic signal; a first finite impulse response type filter for inputting an output signal of the high-pass filter; A second finite impulse response type filter for inputting an output signal, an output signal of the first gain setting device and the first finite impulse response type filter. A first adder that adds the output signals of the output signals of the second gain setting device and a second addition that adds the output signals of the output signals of the second finite impulse response filter Image localization control apparatus including a sound reproduction means for reproducing the output signal of the first adder and the output signal of the second adder, the infinite impulse response filter and the first The gain setting device, the first delay device, the second gain setting device, and the second delay device perform sound image localization control in the low frequency band of the acoustic signal, and the first finite impulse response filter and the second The finite impulse response filter is a sound image localization control device characterized by performing sound image localization control in a high frequency band of an acoustic signal.