Sound field generation system

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sound field generation system that generates a sound field space where the listener can receive spatial sound impression similar to that obtained in the case where the listener listens to music in, for example, a concert hall.

2. Description of the Related Art

As a sound field generation system of this kind, known is a sound field generation apparatus which is disclosed in JP-A-8-130799.

As shown in

FIG. 10A

, the sound field generation apparatus of the related art comprises reverberation generating circuits

1

and

2

which are called SFC processing circuits, filter circuits

3

and

4

, adders

5

and

6

, and amplifiers

7

and

8

, and is configured so as to operate two speakers

9

and

10

to generate sounds, thereby generating a reproduction sound field where spatial sound impression can be obtained.

Each of the reverberation generating circuits

1

and

2

comprises a delaying circuit

13

having multistage delay elements D

1

to Dn shown in FIG.

10

B. Plural delayed outputs with respect to an input signal Sin are added to one another in a predetermined combination relationship, to generate signals for two channels which are provided with reverberation characteristics.

The reverberation generating circuits

1

and

2

further comprise an attenuator and an all-pass filter. The amplitudes and phase characteristics of the signals for two channels are adjusted, so that a right-channel signal SR

1

and a left-channel signal SL

1

are generated and supplied to the adders

5

and

6

.

Each of the filter circuits

3

and

4

is configured by a variable filter which variably adjusts the gain of the right- or left-channel signals SR

1

or SL

1

in the audio frequency band as schematically shown in FIG.

10

C. The output of the filter circuit

3

is supplied to the adders

5

and

6

, that of the filter circuit

4

is supplied to the adder

6

, and an inverted output of the filter circuit

4

is supplied to the adder

5

.

According to this configuration, the adders

5

and

6

output right- and left-channel signals SR

2

and SL

2

which are similar to those recorded in, for example, a specific concert hall, and the signals SR

2

and SL

2

are supplied to the speakers

9

and

10

via the amplifiers

7

and

8

, respectively, thereby generating a reproduction sound field where the listener can receive spatial sound impression similar to that obtained in the case where the listener listens to music in the specific concert hall.

Microphones

11

and

12

pick up reproduced sounds which reach from the speakers

9

and

10

to the ears of the listener. On the basis of obtained pick-up signals PR and PL, an interaural correlation coefficient ρRL is acquired. The frequency characteristics of the filter circuits

3

and

4

are adjusted so that the difference between an interaural correlation coefficient ρRL′ which is previously acquired from the actual transfer function (frequency characteristics) of the specific concert hall, and the interaural correlation coefficient ρRL becomes zero.

The transfer function (frequency characteristics) of a listening room or the like of the listener is different from that of the specific concert hall. Therefore, the frequency characteristics of the filter circuits

3

and

4

are adjusted so as to approximate the interaural correlation coefficient ρRL of the reproduction sound field which is actually generated in the listening room or the like to the interaural correlation coefficient ρRL′ of the specific concert hall, so that, even in a listening room or the like of the listener, a reproduction sound field where spatial sound impression similar to that obtained in the specific concert hall is obtained is generated.

In the sound field generation apparatus according to the related art, the frequency characteristics of the filter circuits

3

and

4

are adjusted in the following manner.

First, it is assumed that the interaural correlation coefficient ρRL′ which is previously obtained from the actual transfer function (frequency characteristics) of the specific concert hall has the characteristics shown in FIG.

11

A. The transfer functions of the reverberation generating circuits

1

and

2

are previously set so as to coincide with the interaural correlation coefficient ρRL′.

As shown in

FIG. 11B

, the passbands of the filter circuits

3

and

4

are set to a narrow band W

1

, and a stationary random signal of the narrow band is supplied as the input signal Sin for adjustment, thereby causing the speakers

9

and

10

to generate reproduced sounds based on the stationary random signal of the narrow band. The microphones

11

and

12

pick up the reproduced sounds, and the interaural correlation coefficient ρRL is acquired on the basis of the obtained pick-up signals PR and PL. Thereafter, the difference between the interaural correlation coefficients ρRL′ and ρRL in the narrow band W

1

is acquired.

Similarly, the passbands of the filter circuits

3

and

4

are sequentially switched to narrow bands W

2

, W

3

, . . . , Wk in this sequence, the speakers

9

and

10

are caused at each of the switching operations to generate reproduced sounds based on the stationary random signal of the narrow band, and the differences between the interaural correlation coefficients ρRL′ and ρRL in the narrow bands W

2

, W

3

, . . . , Wk are acquired.

The gains of the filter circuits

3

and

4

for each of the narrow bands W

1

, W

2

, W

3

, . . . , Wk are adjusted so that the difference between the interaural correlation coefficient ρRL which is actually acquired for each of the narrow bands W

1

, W

2

, W

3

, . . . , Wk, and the interaural correlation coefficient ρRL′ of the concert hall or the like becomes zero, thereby adjusting the frequency characteristics of the filter circuits

3

and

4

in the whole audio frequency band. Namely, the frequency characteristics of the filter circuits

3

and

4

are adjusted in consideration of the transfer function (frequency characteristics) of a listening room or the like of the listener.

When the frequency characteristics of the filter circuits

3

and

4

are adjusted in this way, the adders

5

and

6

outputs the signals SR

2

and SL

2

which are obtained by finely adjusting the signals SR

1

and SL

1

that have been provided with reverberation characteristics of the listening room or the like, on the basis of the output signals of the filter circuits

3

and

4

. The speakers

9

and

10

are caused to generate sounds on the basis of the signals SR

2

and SL

2

, with the result that, even in the listening room or the like of the listener, a reproduction sound field where spatial sound impression similar to that obtained in the specific concert hall is obtained can be generated.

When a stationary random signal of the narrow band is supplied as the input signal Sin for adjustment and the passbands of the filter circuits

3

and

4

are set in the sequence of the narrow bands W

1

, W

2

, W

3

, . . . , Wk as described above, the interaural correlation coefficient ρRL is acquired with including signal components in the overlapping portions of the narrow bands W

1

, W

2

, W

3

, . . . , Wk as indicated by the hatched areas in FIG.

11

C.

When the narrow bands W

1

and W

2

are considered, for example, since the bands overlap with each other, the interaural correlation coefficient ρRL, which is acquired on the basis of the stationary random signal of the narrow band W

1

, contains influences of the stationary random signal in the narrow band W

2

, and the interaural correlation coefficient ρRL, which is acquired on the basis of the stationary random signal of the narrow band W, contains influences of the stationary random signal in the narrow band W

1

. Also the interaural correlation coefficients ρRL which are acquired for the other narrow bands W

2

, W

3

, . . . , Wk contain similar influences, respectively.

Even when the frequency characteristics of the filter circuits

3

and

4

are adjusted so as to perform approximation to the interaural correlation coefficient ρRL′ of the specific concert hall on the basis of the interaural correlation coefficient ρRL which is actually acquired, therefore, an approximation error may occur. As a result, there arises a problem in that a case may occur where, even when the input signal Sin of the actual audio frequency band is supplied to sound the speakers

9

and

10

, the reproduction sound field cannot be approximated to the specific concert hall with sufficiently high accuracy.

SUMMARY OF THE INVENTION

The invention has been conducted in view of the problem of the related art. It is an object of the invention to provide a sound field generation system of a novel configuration which can generate a target sound field space where spatial sound impression simulating that obtained in, for example, a specific concert hall is obtained, with accuracy that is higher than that of the related art.

In order to attain the object, the invention provides a sound field generation system performing interaural correction on at least one input signal to generate a target reproduction sound field, comprising:

at least two sound releasing units;

two input lines through which the one input signal is supplied to the sound releasing units;

a plurality of first band splitting units which are disposed in at least one of the two input lines, and which have different bands from each other;

a plurality of delaying units which are disposed in the first band splitting units, respectively;

a sound picking unit adapted to pick up sounds released from the sound releasing units, at listening positions corresponding to both ears;

a plurality of second band splitting units adapted to band-split outputs of the sound picking units with the same bandwidths as those of the first band splitting units;

a calculating unit adapted to calculate interaural correlation on a basis of band-split outputs from the second band splitting units; and

a controlling unit adapted to control delaying amounts of the delaying units on a basis of a calculation result of the calculating unit.

According to this configuration, the input signal is supplied to the sound releasing units through the first band splitting units and the delaying units, and reproduced sounds are then generated. The sound picking unit at the listening positions pick up the reproduced sounds, and the outputs of the sound picking units are band-split by the second band splitting units. The calculating unit calculates interaural correlation on the basis of each of band-split outputs which have undergone the band split. Based on a result of the calculation, the controlling unit controls the delaying amounts of each of delaying units which is disposed in each of first band splitting units. When the delaying amounts of the delaying units are controlled in this way, a target reproduction sound field can be generated by the reproduced sounds released from the sound releasing units.

When the first and second band splitting units have the same band width, the result of the calculation of the interaural correlation contains no influence between the split bands. When the delaying amounts of the delaying units which are respectively disposed in the first band splitting units are controlled on the basis of the calculation result, the target reproduction sound field can be realized with high accuracy.

The system is configured so that attenuation factor adjusting units is disposed in each of the delaying units and the attenuation factors of the attenuation factor adjusting units are controlled on the basis of the calculation result of the calculating unit. According to this configuration, not only the delaying amounts of the input signal for the respective bands which are set by the first band splitting units, but also the amplitudes are controlled. Therefore, the target reproduction sound field can be generated with higher accuracy.

The invention provides also a sound field generation system performing interaural correction on at least one input signal to generate a target reproduction sound field, comprising:

at least two sound releasing units;

two input lines through which the one input signal is supplied to the sound releasing units;

a plurality of first band splitting units which are disposed in at least one of the two input lines, and which have different bands from each other;

a plurality of delaying units which are disposed in the first band splitting units, respectively;

a storage unit adapted to store transfer functions of spaces between the sound releasing units and listening positions at which reproduced sounds output from the sound releasing units are received, and which correspond to both ears, respectively;

a calculating unit adapted to perform a modulation process on the signal supplied from the input lines toward the sound releasing units on a basis of data indicative of the transfer functions, thereby generating modulated data corresponding to the reproduced sounds at the listening positions, the calculating unit adapted to calculate interaural correlation at the listening positions on a basis of the modulated data; and

a controlling unit adapted to control delaying amounts of the delaying units on a basis of a calculation result of the calculating unit.

According to this configuration, data (modulated data) of the sounds reaching to the listening positions are obtained by performing a modulation process on signals supplied from the input lines toward the sound releasing units on the basis of data indicative of the transfer functions (frequency characteristics) of the spaces between the sound releasing units and the sound picking unit. That is, data of sounds, which are released from the sound releasing units and reach to the listening positions, are acquired as pseudo sound data (modulated data) by so-called simulation. Furthermore, interaural correlation is calculated on the basis of the pseudo sound data (modulated data), and the delaying amounts of the delaying units are optimized based on a result of the calculation. Even when sounds released from the sound releasing units are not actually picked up at the listening positions, therefore, the delaying amounts of the delaying units can be optimized.

Furthermore, the system is characterized in that a plurality of attenuation factor adjusting units are disposed in each of the delaying units and the attenuation factors of the attenuation factor adjusting units are controlled on the basis of the calculation result of the calculating unit. According to this configuration, not only the delaying amounts of the input signal for the respective bands which are set by the first band splitting units, but also the amplitudes are controlled by simulation. Therefore, the target reproduction sound field can be generated with higher accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a block diagram showing the configuration of a sound field generation system of an embodiment.

FIG. 2

is a flowchart illustrating the operation of the sound field generation system of the embodiment.

FIG. 3

is a flowchart further illustrating the operation of the sound field generation system of the embodiment.

FIG. 4

is a characteristic diagram schematically showing an example of a target interaural correlation coefficient.

FIG. 5

is a timing chart schematically showing plural test data which are supplied to an interaural correlation coefficient detecting section.

FIG. 6

are a views showing interaural correlation coefficients and differences which are calculated in optimizing adjustment of delay times of delaying circuits.

FIG. 7

are a views showing a method of optimally adjusting the delay times of the delaying circuits.

FIG. 8

are a views showing a method of optimally adjusting interaural correlation coefficients, differences, and attenuation factors which are calculated in optimizing adjustment of attenuation factors of attenuator circuits.

FIG. 9

is a view schematically showing a transfer function of a reproduction sound field.

FIG. 10

are a view showing the configuration of a sound field generation system according to related art.

FIG. 11

are a view illustrating a problem of the sound field generation system according to related art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, an embodiment of the sound field generation system of the invention will be described with reference to the accompanying drawings.

FIG. 1

is a block diagram showing a configuration of a sound field generation system

14

of the embodiment, and shows as a typical example a configuration in the case where left and right or two-channel speakers

25

and

26

which are disposed in a living room or the like of the user, and which serve as the sound releasing unit are caused to produce sounds on the basis of left and right or two-channel input audio signals SL and SR.

Referring to

FIG. 1

, the sound field generation system

14

comprises: two so-called input lines CHL and CHR for supplying the input audio signals SL and SR to the speakers

25

and

26

; an adjusting circuit

1000

for picking up reproduced sounds generated by the speakers

25

and

26

, and feedback controlling characteristics of attenuator circuits

17

and

18

and delaying circuits

19

and

20

which are disposed in the input lines CHL and CHR; and a noise generator

2000

.

The input lines CHL and CHR comprise: digital amplifiers

33

and

34

for left and right or two channels which are configured by a digital signal processor (DSP), and to which the input audio signals SL and SR that have been analog/digital-converted; filter circuits

15

and

16

; the attenuator circuits

17

and

18

; the delaying circuits

19

and

20

; and adders

21

,

22

,

23

, and

24

.

The filter circuit

15

is configured by a plurality or n number of band-split digital band pass filters BFL

1

to BFLn to which the input audio signal SL is supplied in parallel via the amplifier

33

. The band pass filters BFL

1

to BFLn serving as the first band splitting unit are allocated to split bands which are obtained by splitting the whole audio frequency band into an n number of bands. Specifically, the filter circuit is configured by n(=20) secondary IIR filters.

In the same manner as the filter circuit

15

, the filter circuit

16

is configured by a plurality or n number of band-split digital band pass filters BFR

1

to BFRn. The band pass filters BFR

1

to BFRn are allocated to split bands which are obtained by splitting the whole audio frequency band into an n (=20) number of bands. Namely, the band pass filters BFR

1

to BFRn are set to the same split bands as those of the band pass filters BFL

1

to BFLn.

The attenuator circuit

17

is configured by a plurality or n number of digital attenuators ATL

1

to ATLn which respectively attenuate signals from the band pass filters BFL

1

to BFLn and output attenuated signals. The attenuation factors of the digital attenuators ATL

1

to ATLn can be individually adjusted in a variable manner in accordance with a control by a control section

32

which will be described later.

In the same manner as the attenuator circuit

17

, the attenuator circuit

18

is configured by a plurality or n number of digital attenuators ATR

1

to ATRn which respectively attenuate signals from the band pass filters BFR

1

to BFRn in accordance with a control by the control section

32

which will be described later, and output attenuated signals.

The delaying circuit

19

comprises a plurality or n number of digital delay elements ZL

1

to ZLn, individually delays the signals from the band pass filters BFL

1

to BFLn, and outputs delayed signals.

In the same manner as the delaying circuit

19

, the delaying circuit

20

comprises a plurality or n number of digital delay elements ZR

1

to ZRn, and individually delays the signals from the band pass filters BFR

1

to BFRn, and outputs delayed signals.

The delaying amounts (delay times) of the delay elements ZL

1

to ZLn and ZR

1

to ZRn can be adjusted in accordance with instructions from the control section

32

which will be described later.

The adder

21

adds the n signals output from the delay elements ZL

1

to ZLn together, and supplies a signal SADDL obtained by the addition to the adder

24

.

The adder

22

adds the n signals output from the delay elements ZR

1

to ZRn together, and supplies a signal SADDR obtained by the addition to the adder

23

.

The adder

23

adds the input audio signal SL supplied via the amplifier

33

, and the signal SADDR, and supplies a signal SDVL obtained by the addition to the speaker

25

.

The adder

24

adds the input audio signal SR supplied via the amplifier

34

, and the signal SADDL, and supplies a signal SDVR obtained by the addition to the speaker

26

.

Although not shown, an A/D converter and an output power amplifier are connected between the adder

23

and the speaker

25

so that the signal SDVL which has undergone the digital signal processing is converted into an analog signal and then power-amplified to be supplied to the speaker

25

. Similarly, an A/D converter and an output power amplifier are connected between the adder

24

and the speaker

26

so that the signal SDVR is converted into an analog signal and then power-amplified to be supplied to the speaker

26

.

The noise generator

2000

outputs uncorrelated noises SNZ of a uniform level over the whole audio frequency band, in sound field adjustment which will be described later, and supplies the noises to the amplifiers

33

and

34

via a switching circuit which is not shown. Specifically, in normal audio reproduction, the input audio signals SL and SR are supplied to the amplifiers

33

and

34

, and, in the sound field adjustment which will be described later, the uncorrelated noises SNZ are supplied in place of the input audio signals SL and SR to the amplifiers

33

and

34

.

The adjusting circuit

1000

is configured by: filter circuits

29

and

30

, and an interaural correlation coefficient detecting section

31

which are formed by a digital signal processor (DSP); and the control section

32

comprising a microprocessor (MPU). The circuit further comprises microphones

27

and

28

which pick up reproduced sounds released from the speakers

25

and

26

at respective listening positions (substantially corresponding to the positions of the ears) of the listener.

The filter circuit

29

is configured in the same manner as the filter circuit

15

which is disposed in the input line CHL. Namely, the filter circuit

29

is configured by a plurality or n number of band-split digital band pass filters BFL

1

′ to BFLn′ having the same characteristics as those of the band-split digital band pass filters BFL

1

to BFLn of the filter circuit

15

.

A pick-up signal PL which is output from the microphone

27

is supplied in parallel to the band pass filters BFL

1

′ to BFLn′ serving as the second band splitting unit.

Similarly, the filter circuit

30

has the same configuration as the filter circuit

16

which is disposed in the input line CHR, and is configured by a plurality or n number of band-split digital band pass filters BFR

1

′ to BFRn′ having the same characteristics as those of the band-split digital band pass filters BFR

1

to BFRn of the filter circuit

16

.

A pick-up signal PR which is output from the microphone

28

is supplied in parallel to the band pass filters BFR

1

′ to BFRn′ serving as the second band splitting unit.

Although not shown, the pick-up signals PL and PR are analog/digital-converted by A/D converters, and then supplied to the filter circuits

29

and

30

.

Next, the operation of the thus configured sound field generation system

14

in the sound field adjustment will be described with reference to flowcharts of

FIGS. 2 and 3

.

FIG. 2

shows the operation of adjusting the delay times of the delay elements ZL

1

to ZLn and ZR

1

to ZRn disposed in the delaying circuits

19

and

20

, and

FIG. 3

shows that of adjusting the attenuation factors of the digital attenuators ATL

1

to ATLn and ATR

1

to ATRn disposed in the attenuator circuits

17

and

18

.

When the user operates a remote controller (not shown) to give the control section

32

instructions for performing adjustment so that a sound field where spatial sound impression similar to that in a specific concert hall is obtained is generated in the living room or the like of the user, the sound field adjustment process shown in

FIG. 2

is started.

First, in step S

100

, the control section

32

initializes the interaural correlation coefficients ρRL′ (T

1

, T

2

, . . . , Tn) of a specific concert hall or the like which is designated by the user. The control section

32

previously stores data of interaural correlation coefficients ρRL′ which are acquired from transfer functions (frequency characteristics) of, for example, famous concert halls, and also data of an interaural correlation coefficient ρRL′ of each of plural concert halls. When a specific one of these concert halls is selectively designated by the user, the interaural correlation coefficient ρRL′ (T

1

, T

2

, . . . , Tn) of the designated specific concert hall is initialized.

The initialized interaural correlation coefficient ρRL′ (T

1

, T

2

, . . . , Tn) is called the target interaural correlation coefficient, and, as shown in

FIG. 4

, is a set of coefficient data T

1

, T

2

, . . . , Tn corresponding to the center frequencies of the band-split digital band pass filters BFL

1

′ to BFLn′ and BFR

1

′ to BFRn′ which are disposed at the n number in the filter circuits

29

and

30

.

Next, in step S

102

, the attenuation factors of all the digital attenuators ATL

1

to ATLn and ATR

1

to ATRn are initialized to 0 dB, and, in step S

104

, the delay times of all the delay elements ZL

1

to ZLn and ZR

1

to ZRn are initialized to 0 sec. For the sake of convenience in description, the attenuation factors (0 dB) of the digital attenuators ATL

1

to ATLn are indicated as AL=0, the attenuation factors (0 dB) of the digital attenuators ATR

1

to ATRn are indicated as AR=0, the delay times (0 sec.) of the delay elements ZL

1

to ZLn are indicated as dL=0, and the delay times (0 sec.) of the delay elements ZR

1

to ZRn are indicated as dR=0.

Then, in step S

106

, a variable q is set to “1” in order to designate the first storage region Q

1

of an m number of storage regions Q

1

to Qm which will be described later.

Next, in step S

108

, the initial storage region Qk (=Q

1

) is ensured in a data storage region (not shown) which is disposed in the control section

32

.

Next, in step S

110

, a variable i is set to “1”. The variable i indicates the order in the case where the delay times of the delay elements ZR

1

to ZRn are changed in a step of a predetermined value τ. When i=1, dR=0 is attained. The variable q designates the m number of storage regions Q

1

to Qm, and indicates the order in the case where the delay times of the delay elements ZL

1

to ZLn are changed in a step of the predetermined value τ. When q=1, dL=0 is attained.

Thereafter, in step S

112

, the noise generator

2000

supplies the uncorrelated noises SNZ of the whole audio frequency band to the amplifiers

33

and

34

, to cause the speakers

25

and

26

to generate sounds. During a predetermined time period Tw, the microphones

27

and

28

pick up reproduced sounds released from the speakers

25

and

26

. Then, test data DL

1

(t) to DLn(t) and DR

1

(t) to DRn(t) which are band-split by passing the pick-up signals PL and PR that are obtained as a result of the picking operation, through the band-split digital band pass filters BFL

1

′ to BFLn′ and BFR

1

′ to BFRn′ are supplied to the interaural correlation coefficient detecting section

31

.

The variable t in the test data DL

1

(t) to DLn(t) and DR

1

(t) to DRn(t) indicates that the data are obtained at each reciprocal (sampling period) 1/f of the sampling frequency f which is set on the basis of the sampling theorem. As schematically shown in

FIG. 5

, when the reproduced sounds are picked up for the predetermined time period Tw, therefore, the test data DL

1

(t) consist of a Tw×f number of data, also the test data DR

1

(t) consist of a Tw×f number of data, and also the other DL

2

(t) to DLn(t) and DR

2

(t) to DRn(t) consist of a Tw×f number of data, respectively.

As shown in

FIG. 1

, the test data DL

1

(t) to DLn(t) are data of sounds which are modulated by spatial transfer functions H

12

and H

21

between the speakers

25

and

26

and the microphone

27

, and the test data DR

1

(t) to DRn(t) are data of sounds which are modulated by spatial transfer functions H

11

and H

22

between the speakers

25

and

26

and the microphone

28

.

Next, in step S

114

, the interaural correlation coefficient detecting section

31

calculates an interaural correlation coefficient C

11

between the test data DL

1

(t) and DR

1

(t), and an interaural correlation coefficient C

12

between the test data DL

1

(t) and DR

1

(t) by Ex. (1) below. Then, calculations are conducted in the same manner as described above until an interaural correlation coefficient Cln between the test data DLn(t) and DRn(t) is calculated.

\begin{matrix} Cij = \frac{< DLij (t) \cdot DRij (t) >}{\sqrt{< {&LeftBracketingBar; DLij (t) &RightBracketingBar;}^{2}} > \sqrt{< {&LeftBracketingBar; DRij (t) &RightBracketingBar;}^{2} >}} & (1) \end{matrix}

In Ex. (1) above, the variable j of the interaural correlation coefficient Cij indicates the order of 1 to n of the band-split digital band pass filters BFL

1

′ to BFLn′ and BFR

1

′ to BFRn′, and the variable i indicates the order in the case where the delay times of the delay elements ZR

1

to ZRn are changed in a step of the predetermined value τ. The symbol <> in Ex. (1) indicates an ensemble mean.

As a result, in an initial step S

114

, interaural correlation coefficients (C

11

, C

12

, . . . , Cln) in the case where i=1 and both the delay times dL and dR of the delay elements ZL

1

to ZLn and ZR

1

to ZRn are set to 0 sec. are obtained as shown in the left side of FIG.

6

A.

Next, in step S

116

, differences (T

1

−C

11

), (T

2

−C

12

), . . . , (Tn−Cln) between the target interaural correlation coefficients (T

1

, T

2

, . . . , Tn) and the interaural correlation coefficients (C

11

, C

12

, . . . , Cln) obtained in step S

114

are calculated. Namely, as shown in the right side of

FIG. 6A

, the differences (T

1

−C

11

), (T

2

−C

12

), . . . , (Tn−Cln) corresponding to the interaural correlation coefficients (C

11

, C

12

, . . . , Cln) are obtained.

Then, it is judged in step S

118

whether the variable i is m or i=m or not. If No, the control proceeds to step S

120

to increment the variable i by one, and increase the delay times dR of the delay elements ZR

1

to ZRn by τ. Thereafter, the processes subsequent to step S

112

are repeated.

When the processes of steps S

112

to S

120

are repeated in this way until i=m is judged in step S

118

, interaural correlation coefficients (C

11

, C

12

, . . . , Cln) to (Cm

1

, Cm

2

, . . . , Cmn) in the case where the delay times dL of the delay elements ZL

1

to ZLn are fixed to 0 sec. and the delay times dR of the delay elements ZR

1

to ZRn are gradually increased from 0 sec. in a step of τ sec. are obtained as shown in the left side of FIG.

6

A. Furthermore, differences [(T

1

−C

11

), (T

2

−C

12

), . . . , (Tn−Cln)] to [(T

1

−Cm

1

), (T

2

−Cm

2

), . . . , (Tn−Cmn)] corresponding to the interaural correlation coefficients (C

11

, C

12

, . . . , Cln) to (Cm

1

, Cm

2

, . . . , Cmn) are obtained as shown in the right side of FIG.

6

A.

If it is judged in step S

118

that i=m, the differences [(T

1

−C

11

), (T

2

−C

12

), . . . , (Tn−Cln)] to [(T

1

−Cm

1

), (T

2

−Cm

2

), . . . , (Tn−Cmn)] are stored in step S

122

into the storage region Q

1

.

Then, it is judged in step S

124

whether the variable q is m or q=m or not. If No, the control proceeds to step S

126

where the variable q is incremented by one, the delay times dL of the delay elements ZL

1

to ZLn are increased by τ, and the delay times dR of the delay elements ZR

1

to ZRn are fixed to 0 sec. Thereafter, the processes subsequent to step S

108

are repeated.

When the processes of steps S

108

to S

126

are repeated in this way until q=m is judged in step S

124

, the interaural correlation coefficients and the differences shown in

FIG. 6B

are obtained in the case where the delay times dL of the delay elements ZL

1

to ZLn are fixed to τ sec. and the delay times dR of the delay elements ZR

1

to ZRn are gradually increased from 0 sec. in a step of τ sec., and the interaural correlation coefficients and the differences shown in

FIG. 6C

are obtained in the case where the delay times dL of the delay elements ZL

1

to ZLn are fixed to 2×τ sec. and the delay times dR of the delay elements ZR

1

to ZRn are gradually increased from 0 sec. in a step of τ sec. In the same manner as described above, when the delay times dL of the delay elements ZL

1

to ZLn are fixed to (m−1)×τ sec. and the delay times dR of the delay elements ZR

1

to ZRn are gradually increased from 0 sec. in a step of τ sec., the interaural correlation coefficients and the differences shown in

FIG. 6D

are finally obtained.

Then, the differences [Tj−Cij] which are obtained when the delay times dL are set to τ, 2×τ, . . . , (m−1)×τ are stored into the storage regions Q

2

, Q

3

, . . . , Qm, so that all the storage regions Q

1

, Q

2

, . . . , Qm finally store the differences [Tj−Cij] corresponding to the delay times dL and dR as shown in FIG.

7

A.

If it is judged in step S

124

that the variable q is m or q=m (Yes), the optimum delay times of the delay elements ZL

1

to ZLn and ZR

1

to ZRn are judged and set in step S

128

. The judging and setting processes are performed in the following manner.

In the differences [Tj−Cij] shown in FIG.

7

A and stored in the storage region Q

1

to Qm, first, the minimum value is detected from the differences [T

1

−Cil] corresponding to the first (j=1) delay elements ZL

1

and ZR

1

, and the delay times dL and dR of the delay elements ZL

1

and ZR

1

corresponding to the minimum value are judged and set as the optimum delay times.

When, in the differences [T

1

−Cil] corresponding to the column of j=1 in

FIG. 7A

, the difference (T

1

−C

31

) in the case where the delay times are dL=τ and dR=2×τ is minimum, for example, τ is judged as the optimum delay time of the delay element ZL

1

, 2×τ is judged as the optimum delay time of the delay element ZR

1

, and the optimum delay times are set as shown in

FIGS. 7B and 7C

.

Similarly, when, in the differences [T

2

−Ci

2

] corresponding to the column of j=2 in

FIG. 7A

, the difference (T

2

−C

22

) in the case where the delay times are dL=(m−1)×τ and dR=τ is minimum, (m−1)−τ is judged as the optimum delay time of the delay element ZL

2

, τ is judged as the optimum delay time of the delay element ZR

2

, and the optimum delay times are set as shown in

FIGS. 7B and 7C

.

Similarly, when, in the differences [T

3

−Ci

3

] corresponding to the column of j=3 in

FIG. 7A

, the difference (T

3

−C

23

) in the case where the delay times are dL=0 and dR=τ is minimum, 0 is judged as the optimum delay time of the delay element ZL

3

, τ is judged as the optimum delay time of the delay element ZR

3

, and the optimum delay times are set as shown in

FIGS. 7B and 7C

.

The optimum delay times of the other delay elements are judged and set in the same manner. When, in the differences [Tn−Cin] corresponding to the column of j=n in

FIG. 7A

, the difference (Tn−Cln) in the case where the delay times are dL=2×τ and dR=0 is minimum, for example, 2×τ is judged as the optimum delay time of the delay element ZLn, 0 is judged as the optimum delay time of the delay element ZRn, and the optimum delay times are set as shown in

FIGS. 7B and 7C

.

When the delay times of the delay elements ZL

1

to ZLn and ZR

1

to ZRn are adjusted to the optimum values in this way, the control proceeds to the process shown in FIG.

3

and of adjusting the attenuation factors of the digital attenuators ATL

1

to ATLn and ATR

1

to ATRn.

Steps S

206

to S

228

of

FIG. 3

correspond to steps S

106

to S

128

of FIG.

2

. Namely, the attenuation factors of the digital attenuators ATL

1

to ATLn and ATR

1

to ATRn are adjusted by processes similar to the above-described processes of obtaining the optimum delay times of the delay elements ZL

1

to ZLn and ZR

1

to ZRn.

In

FIG. 3

, the variable r designates the p number of storage regions Q

1

to Qp, and indicates the order in the case where the attenuation factors of the digital attenuators ATL

1

to ATLn of the delaying circuit

19

are changed in a step of a predetermined value (−G) (decibels). The variable i indicates the order in the case where the attenuation factors of the digital attenuators ATR

1

to ATRn of the delaying circuit

20

are changed in a step of the predetermined value (−G) (decibels).

In steps S

206

to S

226

, the processes are performed while the delay elements ZL

1

to ZLn and ZR

1

to ZRn are set to the above-mentioned optimum delay times, the attenuation factors AL of the digital attenuators ATL

1

to ATLn are sequentially changed correspondingly with the variable r or to 0, −G, −2×G, . . . , −(m−1)×G, and the attenuation factors AR of the digital attenuators ATR

1

to ATRn are sequentially changed correspondingly with the variable i or to 0, −G, −2×G, . . . , −(m−1)×G.

As a result, the interaural correlation coefficients Cij and the differences [Tj−Cij] associated with the attenuation factors AL and AR are calculated. The differences [Tj−Cij] are stored into the storage regions Q

1

to Qp with being associated with the attenuation factors AL and AR as shown in FIG.

8

A.

In step S

228

, on the basis of the differences [Tj−Cij] stored in the storage regions Q

1

to Qp, the optimum attenuation factors of the digital attenuators ATL

1

to ATLn and ATR

1

to ATRn are judged and set.

The optimum attenuation factors of the digital attenuators ATL

1

to ATLn and ATR

1

to ATRn are judged in the following manner.

In the differences [Tj−Cij] shown in FIG.

8

A and stored in the storage region Q

1

to Qp, first, the minimum value is detected from the differences [T

1

−Cil] corresponding to the first (j=1) digital attenuators ATL

1

and ATR

1

, and the attenuation factors AL and AR of the digital attenuators ATL

1

and ATR

1

corresponding to the minimum value are judged and set as the optimum attenuation factors.

When, in the differences [T

1

−Ci

1

] corresponding to the column of j=1 in

FIG. 8A

, the difference (T

1

−Cp

1

) in the case where the attenuation factors are AL=0 and AR=−(p−1)×G is minimum, for example, 0 is judged as the optimum attenuation factor of the digital attenuator ATL

1

, −(p−1)×G is judged as the optimum attenuation factor of the digital attenuator ATR

1

, and the optimum attenuation factors are set as shown in

FIGS. 8B and 8C

.

Similarly, when, in the differences [T

2

−Ci

2

] corresponding to the column of j=2 in

FIG. 8A

, the difference (T

2

−C

32

) in the case where the attenuation factors are AL=−2×G and AR=−2×G is minimum, −2×G is judged as the optimum attenuation factor of the digital attenuator ATL

2

, −2×G is judged as the optimum attenuation factor of the digital attenuator ATR

2

, and the optimum attenuation factors are set as shown in

FIGS. 8B and 8C

.

Similarly, when, in the differences [T

3

−Ci

3

] corresponding to the column of j=3 in

FIG. 8A

, the difference (T

3

−C

23

) in the case where the attenuation factors are AL=−(p−1)×G and AR=−G is minimum, −(p−1)×G is judged as the optimum attenuation factor of the digital attenuator ATL

3

, −G is judged as the optimum attenuation factor of the digital attenuator ATR

3

, and the optimum attenuation factors are set as shown in

FIGS. 8B and 8C

.

The optimum attenuation factors of the other digital attenuators are judged and set in the same manner. When, in the differences [Tn−Cin] corresponding to the column of j=n in

FIG. 8A

, the difference (Tn−C

2

n) in the case where the attenuation factors are AL=0 and AR=−G is minimum, 0 is judged as the optimum attenuation factor of the digital attenuator ATLn, −G is judged as the optimum attenuation factor of the digital attenuator ATRn, and the optimum attenuation factors are set as shown in

FIGS. 8B and 8C

.

When the attenuation factors of all the digital attenuators ATL

1

to ATLn and ATR

1

to ATRn have been adjusted by the process of step S

228

, the operation of the noise generator

2000

is stopped, and the input audio signals SL and SR are enabled to be input, thereby completing the sound field adjustment process.

As described above, in the embodiment, the attenuation factors of the attenuator circuits

17

and

18

, and the delay times of the delaying circuits

19

and

20

are set so as to approximate the interaural correlation coefficient τRL which is actually acquired from the reproduced sounds, to the interaural correlation coefficient τRL′ of a specific concert hall or the like. When the speakers

25

and

26

are caused to generate sounds on the basis of the input audio signals SL and SR after the sound field adjustment, a reproduction sound field where spatial sound impression similar to that in the specific concert hall is obtained can be generated even in the living room or the like of the user (listener).

In the related art, in the sound field adjustment, speakers are caused to generate sounds by passing a stationary random signal of the narrow band through the band pass filters which are set to a narrow band, and an actual interaural correlation coefficient is obtained from reproduced sounds which are generated by the sounding. Consequently, there may arise a case where an approximation error occurs when a reproduction sound field in a listening room of the listener or the like is approximated to an interaural correlation coefficient of a concert hall or the like.

In contrast to the related art, in the embodiment, the uncorrelated noises SNZ of the whole audio frequency band are used as the input signal for adjustment, and the uncorrelated noises SNZ are passed through all of the band pass filters BFL

1

to BFLn and BFR

1

to BFRn, the digital attenuators ATL

1

to ATLn and ATR

1

to ATRn, and the digital delay elements ZL

1

to ZLn and ZR

1

to ZRn, and then supplied to the speakers

25

and

26

. On the basis of the test data DL

1

(t) to DLn(t) and DR

1

(t) to DRn(t) which are obtained by band-splitting the reproduced sounds generated by the supply, by the band-split digital band pass filters BFL

1

′ to BFLn′ and BFR

1

′ to BFRn′, the actual interaural correlation coefficient τRL is obtained.

When the actual interaural correlation coefficient ρRL is obtained on the basis of the test data DL

1

(t) to DLn(t) and DR

1

(t) to DRn(t) which are obtained by performing band-splitting by the band-split digital band pass filters BFL

1

′ to BFLn′ and BFR

1

′ to BFRn′ that are identical with the band pass filters BFL

1

to BFLn and BFR

1

to BFRn, the interaural correlation coefficient ρRL is actually obtained under the same conditions as those in usual reproduction in which the speakers

25

and

26

are caused to generate sounds by the input audio signals SL and SR.

When the attenuation factors of the digital attenuators ATL

1

to ATLn and ATR

1

to ATRn and the delay times of the delay elements ZL

1

to ZLn and ZR

1

to ZRn are set so as to approximate the interaural correlation coefficient ρRL to the target interaural correlation coefficient ρRL′ of a concert hall or the like, the approximation error can be largely reduced, so that the target sound field where spatial sound impression simulating that in a specific concert hall or the like is obtained can be generated.

In the embodiment, the uncorrelated noises SNZ are used as the input signal in the adjustment. The invention is not restricted to this. As the input signal, any appropriate signal may be used as far as the signal has signal components over the whole audio frequency band.

In the embodiment, the filter circuits

15

and

16

, the attenuator circuits

17

and

18

, the delaying circuits

19

and

20

, and the adders

21

to

24

are disposed in the input lines CHL and CHR for two channels. Alternatively, a filter circuit, an attenuator circuit, a delaying circuit, and an adder may be disposed only in one of the input lines.

For example, a configuration in which the filter circuit

16

, the attenuator circuit

18

, the delaying circuit

20

, and the adder

22

are omitted, the outputs of the amplifiers

33

and

34

are supplied to the adder

23

, and the output of the adder

21

and that of the amplifier

34

are supplied to the adder

24

may be employed. Also in the configuration, a sound field where spatial sound impression is obtained can be generated by reproduced sounds released from the speakers

25

and

26

.

In the embodiment described above, in normal audio reproduction, the left and right or two-channel input audio signals SL and SR are supplied to enable the speakers

25

and

26

to perform stereophonic reproduction. The invention is not restricted to this. Even when a monophonic audio signal is supplied as the audio signals SL and Sr, a reproduction sound field where spatial sound impression is obtained can be generated.

In the embodiment, the two-channel stereophonic audio system has been described. The invention can be applied also to a so-called multi-channel audio system having a larger number of channels.

In the embodiment, as described above, the speakers

25

and

26

are caused to generate sounds in the sound field adjustment, the interaural correlation coefficient is acquired on the basis of the reproduced sounds which are actually modulated by the transfer functions (frequency characteristics) H

11

, H

12

, H

21

, and H

22

of the spaces such as the living room of the user, and the attenuation factors of the digital attenuators ATL

1

to ATLn and ATR

1

to ATRn, and the delay times of the delay elements ZL

1

to ZLn and ZR

1

to ZRn are optimized on the basis of the interaural correlation coefficient.

Alternatively, the speakers

25

and

26

may not be caused to generate sounds, and the reproduced sounds which are modulated by the transfer functions H

11

, H

12

, H

21

, and H

22

of the living room or the like may not be picked up. In the alternative, transfer function data [H] in the form of a regular matrix and indicative of the transfer functions H

11

, H

12

, H

21

, and H

22

of the space such as the living room may be previously stored in a predetermined storage region of the control section

32

, and the attenuation factors of the digital attenuators ATL

1

to ATLn and ATR

1

to ATRn, and the delay times of the delay elements ZL

1

to ZLn and ZR

1

to ZRn may be optimized by simulation.

Specifically, a first modification of the embodiment may be configured in the following manner. In the sound field adjustment process which has been described with reference to

FIGS. 2 and 3

, when the attenuation factors of all the digital attenuators ATL

1

to ATLn and ATR

1

to ATRn are set to 0 dB and the delay times of all the delay elements ZL

1

to ZLn and ZR

1

to ZRn are set to 0 sec., the frequency characteristics of the signals SDVL and SDVR supplied to the speakers

25

and

26

, and the pick-up signals PL and PR picked-up by the microphones

27

and

28

are calculated. Based on results of these calculations, a transfer function [H] of the space configured by the speakers

25

and

26

, the living room, and the like is acquired, and the data [H] of the transfer function are stored in a predetermined storage region of the control section

32

. Namely, transfer function data [H] such as shown in

FIG. 9

are previously stored.

When, after the first sound field adjustment process is performed, the user gives instructions for again performing sound field adjustment with designating another concert hall or the like, the output signals SDVL and SDVR of the adders

23

and

24

are not supplied to the speakers

25

and

26

, and the pick-up signals PL and PR are calculated by simulation based on Ex. (2) below. In other words, pseudo pick-up signals PL and PR are acquired by simulation.

Furthermore, test data DL

1

(t) to DLn(t) and DR

1

(t) to DRn(t) are calculated by applying the calculated pick-up signals PL and PR to the filter circuits

29

and

30

. The interaural correlation coefficients Cij and the differences [Tj−Cij] are calculated on the basis of the test data DL

1

(t) to DLn(t) and DR

1

(t) to DRn(t). Then, the attenuation factors of the digital attenuators ATL

1

to ATLn and ATR

1

to ATRn, and the delay times of the delay elements ZL

1

to ZLn and ZR

1

to ZRn are optimized on the basis of the differences [Tj−Cij].

Namely, when instructions for again performing sound field adjustment are given, the output signals SDVL and SDVR of the adders

23

and

24

are not supplied to the speakers

25

and

26

, the pseudo pick-up signals PL and PR are calculated by simulation based on Ex. (2) below, and the pick-up signals PL and PR which are acquired by the calculation are used as the actual pick-up signals to be applied to the filter circuits

29

and

30

.

\begin{matrix} (\begin{matrix} PL \\ PR \end{matrix}) = (\begin{matrix} H11 & H12 \\ H21 & H22 \end{matrix}) (\begin{matrix} SDVL \\ SDVR \end{matrix}) & (2) \end{matrix}

In this way, after the transfer function data [H] of the space configured by the speakers, the living room, and the like are once acquired, sound field adjustment is performed by simulation using the transfer function data [H]. According to this configuration, it is not required to cause the speakers

25

and

26

to generate sounds each time when sound field adjustment is to be performed, and hence improvement of convenience of the user and the like can be enabled.

In the first modification described above, the pseudo pick-up signals PL and PR which are acquired by the simulation are applied to the filter circuits

29

and

30

to further acquire the test data DL

1

(t) to DLn(t) and DR

1

(t) to DRn(t). Alternatively, transfer function data [H] including the frequency characteristics of the space of the living room and the like and those of the filter circuits

29

and

30

may be previously stored, the output signals SDVL and SDVR of the adders

23

and

24

may be applied to the transfer function data [H] to directly acquire test data DL

1

(t) to DLn(t) and DR

1

(t) to DRn(t), and the interaural correlation coefficient may be calculated on the basis of the test data DL

1

(t) to DLn(t) and DR

1

(t) to DRn(t).

In a second modification of the embodiment, transfer function data [H] of the space configured by the speakers

25

and

26

, the living room of the user, and the like are previously stored in a predetermined storage region of the control section

32

. When the user gives instructions for performing sound field adjustment with designating a desired concert hall or the like, the pick-up signals PL and PR may be calculated from the beginning by simulation based on Ex. (2) above. The pick-up signals PL and PR which are acquired by the calculation may be used as the actual pick-up signals to be applied to the filter circuits

29

and

30

.

In the first modification, the speakers

25

and

26

are caused to generate sounds in the first sound field adjustment. By contrast, in the second modification, sound field adjustment is performed without causing the speakers

25

and

26

to generate sounds, and by only simulation using the transfer function data [H] which are previously stored.

In the second modification, plural kinds of transfer function data [H] in which housing conditions and the like are considered are previously stored into the control section

32

at the factory shipment, and the user selectively designates a transfer function suitable for the living room or the like of the user, from the plural kinds of transfer functions by using a remote controller or the like.

According to the second modification, improvement of convenience of the user and the like can be enabled, and a reproduction sound field where the user can receive spatial sound impression similar to that obtained in the case where the user listens to music in a desired concert hall can be provided simply by selectively designating a transfer function suitable for the living room or the like of the user. Furthermore, the microphones

27

and

28

shown in

FIG. 1

can be eliminated.

In the second modulation also, in place of applying the pseudo pick-up signals PL and PR which are acquired by the simulation to the filter circuits

29

and

30

to further acquire the test data DL

1

(t) to DLn(t) and DR

1

(t) to DRn(t), transfer function data [H] including the frequency characteristics of the space of the living room and the like and those of the filter circuits

29

and

30

may be previously stored, the output signals SDVL and SDVR of the adders

23

and

24

may be applied to the transfer function data [H] to directly acquire test data DL

1

(t) to DLn(t) and DR

1

(t) to DRn(t), and interaural correlation coefficient may be calculated on the basis of the test data DL

1

(t) to DLn(t) and DR

1

(t) to DRn(t).

As described above, in the sound field generation system of the invention, the input signal is supplied to the sound releasing units through the first band splitting units and the delaying units, and reproduced sounds are picked up. Interaural correlation is calculated on the basis of band-split outputs which are obtained by band-splitting the reproduced sounds by the second band splitting units having the same bandwidths as those of the first band splitting units. Based on a result of the calculation, the delaying amounts of the delaying units which are disposed in the first band splitting unit, respectively, are controlled. Therefore, the result of the calculation of the interaural correlation contains no influence between the split bands, and the target reproduction sound field can be realized with high accuracy.

The system is configured so that the attenuation factor adjusting units is disposed in the delaying units, respectively and the attenuation factors of the attenuation factor adjusting units are controlled on the basis of the calculation result of the calculating unit. The delaying amount and amplitude controls are conducted on the input signal of the respective bands set by the first band splitting units. Therefore, the target reproduction sound field can be generated with higher accuracy.

The system further comprises the storage unit for storing data indicative of transfer functions of spaces between the sound releasing unit and listening positions at which reproduced sounds output from the sound releasing units are received, and which correspond to the ears, respectively. By simulation, the signal supplied from the input lines toward the sound releasing units is subjected to a modulation process on the basis of data indicative of the transfer functions, to acquire modulated data corresponding to the reproduced sounds at the listening positions, interaural correlation at the listening positions is calculated on the basis of the modulated data, and delaying amounts of the delaying units are controlled on the basis of a result of the calculation. Even when sounds released from the sound releasing units are not actually picked up by sound picking units such as microphones, therefore, the delaying amounts of the delaying units can be optimized.

When a process of correcting a sound field is performed by simulation in this way, it is possible to attain effects such as that improvement of convenience of the user and the like can be enabled, and that a sound field where the user can receive spatial sound impression similar to that obtained in the case where the user listens to music in a desired concert hall or the like can be provided simply by selectively designating a transfer function suitable for the living room or the like of the user.

Furthermore, the attenuation factor adjusting units are disposed in the delaying unit, respectively, and the attenuation factors of the attenuation factor adjusting units are controlled on the basis of the calculation result of interaural correlation at the listening positions acquired by simulation. Therefore, not only optimization of the delaying amounts in the input lines, but also optimum control of the amplitudes can be performed, so that the target reproduction sound field can be generated with higher accuracy. Moreover, improvement of convenience of the user and the like can be enabled.

Number	Name	Date	Kind
5381482	Matsumoto	Jan 1995	A
5604810	Yanagawa	Feb 1997	A
5796845	Serikawa	Aug 1998	A
6035045	Fujita et al.	Mar 2000	A

Number	Date	Country
0 827 361	Mar 1998	EP
8-130799	May 1996	JP

Sound field generation system

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Term Extension

Abstract

Description

Claims

Priority Claims (1)

US Referenced Citations (4)

Foreign Referenced Citations (2)