JPH09215100A - Sound image controller and sound image control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sense of hearing sound as if coming from outside the head even when a listener hears the sound with a headphone by localizing a sound image at an optional position through 2-channel speaker reproduction. SOLUTION: A 1st signal generating means adds a 1st composite sound signal from a 1st signal processing means and a 1st cancelling signal from a cancellation signal generating means to generate a 1st channel signal. A 2nd signal generating means subtracts the cancellation signal from a 2nd composite sound signal from a 2nd signal processing means to generate a 2nd channel signal. A characteristic of a head sound transmission function is reflected on the 1st channel signal and the 2nd channel signal outputted from the sound image controller. The difference signal is outputted in phase for the 1st channel and an inverted phase for the 2nd channel. Since the cancellation point of the signals is formed in an acoustic space between both speakers in this way, a sound image is localized at the outside of both speakers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound image control device and a sound image control method capable of localizing a sound image at an arbitrary position in a sound field in both cases of listening to a speaker and listening to headphones.

[0002]

2. Description of the Related Art Conventionally, as a technique for localizing a sound image by reproducing a two-channel speaker, a technique using convolution of a head acoustic transfer function in the time domain and crosstalk cancellation is known (for example, "about RSS"). ,
Roland Corporation, Journal of Acoustical Society of Japan, Vol. 48, No. 9). As a similar technique, there is known a technique in which a sound image is localized outside the speaker by mixing opposite-phase sounds (for example, “sound image operating device and sound image enlarging method (SOUND
IMAGE MANIPULATION APPARATUS AND METHOD FOR SOUND
IMAGE ENHANCEMENT) ”, Desper Products, WO9
4/16538).

[0003]

However, in the technique of localizing a sound image by convolution of the head acoustic transfer function in the time domain and crosstalk cancellation, the delay and the FIR filter are used for the crosstalk cancellation, so that the hardware The amount becomes huge. Therefore, it is not possible to cancel the crosstalk completely due to the hardware limitation.

In addition, it is difficult to localize the sound image at an arbitrary place by the technique of mixing the sounds of opposite phases and localizing the sound image to the outside of the speaker, and the sound image is localized at a position far from the listener. It is difficult to let In addition, this technique has a drawback that a sound image cannot be localized when reproduced by headphones.

Further, in the conventional sound image control device, the sound image is moved by a method of replacing the coefficient corresponding to the current sound image position with the coefficient corresponding to the new sound image position. However, in this method, when the moving distance of the sound image is increased, the signal generated by the sound image control device changes abruptly, which causes a problem that noise is generated.

Therefore, according to the present invention, the sound image can be localized at an arbitrary position including a position far from the listener by reproducing the sound of the two channels, and the sound image can be obtained even when the sound is heard through headphones. An object is to provide a control device and a sound image control method.

[0007]

In order to solve the above problems, the sound image control apparatus according to the first aspect of the present invention uses an input signal as a first head acoustic transfer function as shown in FIG. First signal processing means for generating a first direct sound signal corresponding to the direct sound and a first composite sound signal corresponding to the composite sound of the direct sound and the reflected sound by processing using the first direct sound signal; A second direct sound signal corresponding to the direct sound and a second composite sound corresponding to the composite sound of the direct sound and the reflected sound by processing the input signal using the second head acoustic transfer function. A second signal processing means for generating a signal and a difference signal by subtracting the second direct sound signal from the second signal processing means from the first direct sound signal from the first signal processing means. And a difference signal generating means for generating a difference signal from the difference signal generating means A cancellation signal generating means for generating a first cancellation signal and a second cancellation signal for controlling, a first composite sound signal from the first signal processing means and a first cancellation sound signal from the cancellation signal generating means. And a cancellation signal from the second composite sound signal from the second signal processing means and a cancellation signal from the cancellation signal generation means. A second signal generating means for subtracting the two cancellation signals to thereby generate a second channel signal.

The first head-related acoustic transfer function used in the first signal processing means is a transfer from the sound source to one ear of the human (strictly "eardrum", the same applies below), for example, the left ear. The second head acoustic transfer function used in the second signal processing means is a function that represents a system and represents a transfer system from the sound source to the other ear of the human, for example, the right ear. In the following, the first and second head acoustic transfer functions are collectively referred to as "head acoustic transfer function". The head acoustic transfer function is a transfer function that reflects reflection, diffraction, resonance, etc. of the head, auricle, shoulder and the like. This head acoustic transfer function can be obtained by measurement.

The first direct sound signal output from the first signal processing means is a signal indicating the first direct sound directly reaching the one ear of the human from the sound source, and is output from the second signal processing means. The output second direct sound signal is a signal indicating the second direct sound that directly reaches the other ear of the human from the sound source. These first and second direct sounds are simply referred to as "direct sounds".

In contrast to this direct sound, a first reflected sound that reaches one ear of a human after the sound emitted from the sound source is reflected by an obstacle and a second reflected sound that reaches the other ear Exists. These first and second reflected sounds are simply “reflected sounds”
Collectively. The reflected sound includes early reflected sound and reverberant sound. When sound is emitted from the sound source, the direct sound first reaches the human ear, and then the reflected sound reaches it. The first composite sound signal is the first composite sound signal that reaches the one ear of the human from the sound source.
Is a signal indicating a first composite sound in which the first direct sound and the first reflected sound are combined, and the second composite sound signal is the second direct sound reaching the other human ear from the sound source and the second direct sound. It is a signal indicating a second composite sound in which the two reflected sounds are combined. These first and second composite sounds are simply referred to as "composite sounds".

The direct sound signal is produced, for example, on the basis of the head impulse response (hereinafter referred to as the "head impulse response of the direct part") from the time when the impulse is input until about 4.5 milliseconds have elapsed. You can Further, the composite sound signal includes, for example, a head impulse response of the direct part and a head impulse response (hereinafter, “head impulse response of the reflection part”) of about 4.5 to 21 milliseconds after the impulse is input.
It can be produced based on

More specifically, the direct sound signal can be produced by passing the input signal through, for example, an eighth-order IIR type filter. The reflected sound signal is obtained by passing the input signal through, for example, a 6th-order IIR type filter,
It can be manufactured by taking out the output of the R-type filter from a plurality of taps, amplifying each, and adding them. Further, the composite sound signal can be produced by amplifying the direct sound signal and adding each delayed signal to the reflected sound signal.

The difference signal generating means can be composed of, for example, a subtractor and a filter. This difference signal generating means is
The difference signal is generated by subtracting the second direct sound signal from the first direct sound signal and filtering it. This difference signal is supplied to the cancellation signal generating means. As the filter, for example, a first-order IIR type low-pass filter can be used. By mixing the difference signal and the composite sound signal, it becomes possible to localize the sound image outside both speakers in the case of speaker reproduction of two channels.

The cancellation signal generating means can be composed of, for example, a first delay device and a second delay device. The cancellation signal generation means supplies the first cancellation signal obtained by delaying the difference signal by the first delay device to the first signal generation device, and delays the difference signal by the second delay device. The second cancellation signal obtained by is supplied to the second signal generating means.

The first signal generating means can be composed of, for example, an adder. The first signal generating means is the first
The first composite sound signal from the signal processing means and the first cancellation signal from the cancellation signal generating means are added to generate the first channel signal.

The second signal generating means can be composed of, for example, a subtractor. The second signal generating means is the second
The second canceling signal from the canceling signal generating means is subtracted from the second composite sound signal from the signal processing means to generate the second channel signal.

Since the characteristics of the head acoustic transfer function are reflected in the signal for the first channel and the signal for the second channel output from this sound image control device, both of these signals are converted into acoustic signals by headphones. , The sound image is localized by the binaural effect.

Further, the first composite sound signal and the first canceling signal generated based on the difference signal are added to generate a signal for the first channel, and from the second composite sound signal, Since the second canceling signal generated based on the difference signal is subtracted to generate the second channel signal, the difference signal is output in the positive phase in the first channel and in the negative phase in the second channel. To be done. As a result, a signal cancellation point can be formed in the acoustic space between the speakers, so that the sound image can be localized outside the speakers.

Further, since the first or second cancellation signal output from the cancellation signal generating means is generated by delaying the difference signal, the sound space in which the sound should be canceled by changing the delay amount. Can be moved from the left ear to the right ear. For example, when it is desired to localize the sound image on the left side, the position of the sound image can be felt more to the left by forming an acoustic space in which the sound should be canceled near the right ear. Further, when it is desired to localize the sound image on the right side, the position of the sound image can be felt in the right direction by forming the acoustic space in which the sound should be canceled near the left ear. Furthermore, when it is desired to localize the sound image in the front direction (front or rear), the sound image can be localized in front front or rear by forming an acoustic space in which the sound should be canceled in the center of the head.

The acoustic space for canceling the sound and the delay amount of the difference signal are controlled so as to have the following relationship. That is, when the sound image is localized in the lateral direction, the delay amount is set so that the acoustic space in which the sound should be canceled is formed at the position of the ear on the opposite side. Then, the delay amount is set to zero. As a result, the localization of the sound image becomes clear and a sense of long distance occurs.

In the sound image control device according to the first aspect,
Since the first and second cancellation signals for forming the acoustic space for canceling the sound and the first and second composite sound signals having the above-mentioned binaural effect are overlapped and output,
The sound image can be clearly localized in all directions.

In the sound image control device according to the first aspect,
The cancellation signal generating means may be configured to switch whether to output the difference signal. According to this configuration, when the difference signal is output, it is suitable for listening to the speaker, and when the difference signal is not output, it is suitable for listening to the headphones.

For the same purpose, the sound image control apparatus according to the second aspect of the present invention is, as shown in FIG. 2, a first weighting means for first weighting an input signal, and the first weighting means. Processing the signal from the weighting means using the first head acoustic transfer function to generate a first direct sound signal corresponding to the direct sound and a first direct sound signal corresponding to the composite sound of the direct sound and the reflected sound. First signal processing means for generating a composite sound signal of
By processing the signal from the weighting means of the second head acoustic transfer function using the second head acoustic transfer function, the second direct sound signal corresponding to the direct sound and the second direct sound corresponding to the composite sound of the direct sound and the reflected sound.
Second signal processing means for generating a composite sound signal of, and second weighting means for performing a second weighting on the input signal,
By processing the signal from the second weighting means using the first head acoustic transfer function, a third direct sound signal corresponding to the direct sound and a composite sound of the direct sound and the reflected sound are processed. Corresponding to the direct sound by processing the signal from the third signal processing means for generating the third composite sound signal and the signal from the second weighting means using the second head acoustic transfer function. Fourth signal processing means for generating a fourth direct sound signal and a fourth composite sound signal corresponding to a composite sound of the direct sound and the reflected sound, and a first signal processing means for outputting the first signal from the first signal processing means. Based on the addition result of the direct sound signal and the third direct sound signal from the third signal processing means, the second direct sound signal from the second signal processing means and the third direct sound signal from the fourth signal processing means. Difference signal generating means for generating a difference signal by subtracting the addition result with the fourth direct sound signal; A cancellation signal generating means for delaying the difference signal from the generating means to generate a first cancellation signal and a second cancellation signal for controlling the cancellation position, and a first synthesis from the first signal processing means. Adding the sound signal, the third synthesized sound signal from the third signal processing means, and the first cancellation signal from the cancellation signal generating means,
Thus, the first signal generating means for generating the signal for the first channel, the second synthesized sound signal from the second signal processing means, and the fourth synthesized sound signal from the fourth signal processing means. And a second signal generation means for subtracting the second cancellation signal from the cancellation signal generation means to generate a signal for the second channel.

The sound image control device according to the second aspect of the present invention is configured by including two series of functional blocks equivalent to those of the sound image control device according to the first aspect described above. The first series of functional blocks includes first weighting means, first signal processing means and second signal processing means, part of difference signal generation means, part of cancellation signal generation means, and first signal generation. It is composed of a part of the means and a part of the second signal generating means. The functional block of the second series is the second weighting means,
Third signal processing means and fourth signal processing means, part of difference signal generation means, part of cancellation signal generation means, part of first signal generation means and part of second signal generation means It is composed of. Therefore, one sound image can be localized by the first functional block, and another sound image can be localized by the second functional block.

Now, assume that the weighting coefficient is a value in the range of "0-1". Here, the first weight given to the first weighting means
If the weighting coefficient of is set to "1" and the second weighting coefficient given to the second weighting means is set to "0", it is equal to the state in which the second series functional block does not exist. Similarly to the sound image control device according to the first aspect, the first
One sound image is localized only by the functional blocks of the series. From this state, the first weighting coefficient is gradually reduced,
When the weighting factor of is gradually increased, the sound image formed by the first series of functional blocks gradually decreases, and the sound image formed by the second series of functional blocks gradually increases. Then, if the first weighting coefficient given to the first weighting means is "0" and the second weighting coefficient given to the second weighting means is "1", it means that the first functional block does not exist. They are equal, and like the sound image control device according to the first aspect of the present invention described above, one sound image is localized only by the functional blocks of the second series.

The first weighting means can be composed of, for example, a multiplier. The signal subjected to the first weighting by the first weighting means is supplied to the first signal processing means and the second signal processing means. Similarly, the second weighting means can be composed of, for example, a multiplier. The signal subjected to the second weighting by the second weighting means is supplied to the third signal processing means and the fourth signal processing means.

The first signal processing means and the third signal processing means are the same as the first signal processing means of the sound image control device according to the first aspect. The second signal processing means and the fourth signal processing means are the same as the second signal processing means of the sound image control device according to the first aspect.

The difference signal generating means can be composed of, for example, an adder, a subtractor and a filter. The difference signal generation means subtracts a signal obtained by adding the second direct sound signal and the fourth direct sound signal from a signal obtained by adding the first direct sound signal and the third direct sound signal. . Others are the same as the difference signal generating means of the sound image control device of the first aspect.

The cancellation signal generation means is the same as the cancellation signal generation means of the sound image control apparatus of the first aspect.
The first signal generating means can be composed of, for example, an adder. The first signal generation means includes a first composite sound signal from the first signal processing means, a third composite sound signal from the third signal processing means, and a first composite sound signal from the cancellation signal generation means. The cancellation signal is added to generate a signal for the first channel.

The second signal generating means can be composed of, for example, an adder and a subtractor. The second signal generation means outputs from a signal obtained by adding the second composite sound signal from the second signal processing means and the fourth composite sound signal from the fourth signal processing means, from the cancellation signal generation means. The second cancellation signal is subtracted to generate the second channel signal.

According to the sound image control device of the second aspect, when the sound image is moved from a certain position to another position,
By gradually increasing the weighting of the first weighting means and gradually decreasing the weighting of the second weighting means, or vice versa, it is possible to suppress the occurrence of noise due to the replacement of the coefficients of the sound image control device, The sound image can be moved smoothly. In addition, since noise can be suppressed even if the sound image is moved significantly, there is no need to prepare coefficients corresponding to many sound image positions as in the conventional case,
The amount of coefficients to be prepared in advance can be reduced.

A plurality of means constituting the sound image control device according to the first aspect and the sound image control device according to the second aspect are
Digital signal processor (hereinafter referred to as "DSP")
Can be configured. Further, these plural means can be configured by hardware. Further, it is possible to configure a part of these plural means by a DSP and the other portion by hardware. Further, each of the respective means can be entirely configured by a DSP or hardware, or a part thereof can be configured by a DSP and the other portion can be configured by hardware.

The filter coefficient supplied to the filter, the multiplication coefficient supplied to the multiplier, the coefficient supplied to the delay device, and the like included in each of the above means can be configured to be changeable. This is because the coefficient is stored in a storage means such as a random access memory (hereinafter referred to as “RAM”) or a read-only memory (hereinafter referred to as “ROM”) provided in the sound image control device, and the sound image position When designated, the coefficient corresponding to the designation is read from the storage means,
It may be configured so as to be supplied to a filter, a multiplier, a delay device and the like.

For the same purpose as described above, the first aspect of the present invention
In the sound image control method according to the aspect (1), the input signal is processed using the first head acoustic transfer function to generate a first direct sound signal corresponding to the direct sound, and a composite sound of the direct sound and the reflected sound. And a first direct sound signal corresponding to the direct sound by processing the input signal using the second head acoustic transfer function. A second composite sound signal corresponding to the composite sound of the reflected sound is generated, and a difference signal is generated by subtracting the second direct sound signal from the first direct sound signal, and the difference signal is delayed. Generate a first canceling signal and a second canceling signal for controlling the canceling position, and add the first composite sound signal and the first canceling signal, and thus for the first channel A signal is generated and the second cancellation signal is subtracted from the second composite sound signal to obtain a second chirp signal. It is configured to generate a tunnel signal.

According to the sound image control method of the first aspect, the same operation and effect as those of the sound image control device of the first aspect described above are exhibited.

Further, for the same purpose, the sound image control method according to the second aspect of the present invention weights the input signal with the first weighting, and outputs the first weighted signal with the first head acoustic signal. The first direct sound signal corresponding to the direct sound and the first composite sound signal corresponding to the composite sound of the direct sound and the reflected sound are generated by processing using the transfer function, and the first direct sound signal is generated. By processing the weighted signal using the second head acoustic transfer function, the second direct sound signal corresponding to the direct sound and the second direct sound signal corresponding to the composite sound of the direct sound and the reflected sound are processed. A direct sound is generated by generating a composite sound signal, applying a second weighting to the input signal, and processing the second weighted signal using a first head acoustic transfer function. Third
Of the direct sound signal and a third composite sound signal corresponding to the composite sound of the direct sound and the reflected sound, and using the second head acoustic transfer function to generate the second weighted signal. By processing, the fourth direct sound signal corresponding to the direct sound and the fourth composite sound signal corresponding to the composite sound of the direct sound and the reflected sound are generated, and the first direct sound signal and the A difference signal is generated by subtracting the addition result of the second direct sound signal and the fourth direct sound signal from the addition result of the third direct sound signal,
A first cancellation signal and a second cancellation signal for delaying the difference signal to control a cancellation position are generated, and the first synthesized sound signal, the third synthesized sound signal and the first cancellation signal are generated. The signals are added to generate a signal for the first channel, and the second cancellation signal is subtracted from the addition result of the second synthesized sound signal and the fourth synthesized sound signal, and thus the second It is configured to generate a signal for the channel.

According to the sound image control method of the second aspect, the same action and effect as those of the sound image control apparatus of the first aspect described above are exhibited.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a sound image control device and a sound image control method of the present invention will be described in detail below with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram showing a configuration of a sound image control apparatus according to a first aspect of the present invention. First signal processing means, second signal processing means, difference signal generation means, cancellation signal generation means, first signal processing means shown in FIG.
Each block of the signal generating means and the second signal generating means is assumed to be realized by a DSP.

In the first embodiment, the first channel signal is the left channel signal and the second channel signal is the right channel signal. Therefore, the first composite sound signal and the first direct sound signal generated by the first signal processing means are the left composite sound signal and the left direct sound signal, respectively.
Similarly, the second composite sound signal and the second direct sound signal generated by the second signal processing means are a right composite sound signal and a right direct sound signal, respectively. The first cancellation signal generated by the cancellation signal generation means is a left cancellation signal, and the second cancellation signal is a right cancellation signal.

FIG. 3 is a block diagram showing the configuration of the first signal processing means and the second signal processing means. The configuration of the first signal processing means is the same as that of the second signal processing means, but the coefficients (filter coefficient, multiplication coefficient, delay coefficient) given to them are different. That is, the first signal processing means is provided with a coefficient for approximating the first head acoustic transfer function, and the second processing means is provided with a coefficient for approximating the second head acoustic transfer function. Given. Therefore, in the following description, the term "signal processing means" will be simply used unless otherwise specified.

The signal processing means shown in FIG. 3 is roughly divided into a direct sound generating system and a reflected sound generating system. The direct sound generation system includes an eighth-order IIR filter 10, a multiplier 11, and a delay device 12. FIG. 4 shows an example of the configuration of the 8th-order IIR filter 10. The 8th-order IIR type filter 10 is a well-known filter in which a configuration called a standard type of an IIR system is connected in series. The multiplier 11 amplifies the signal passed through the eighth-order IIR filter 10 according to the multiplication coefficient. The output of the multiplier 11 is the delay device 1
2 is supplied to the external difference signal generating means (see FIG. 1) as the first or second direct sound signal.
The delay device 12 delays the direct sound signal from the multiplier 11 by a time corresponding to the delay coefficient. The signal from the delay device 12 is supplied to the adder 24.

The reflected sound generating system of the signal processing means has a sixth-order I
IR type filter 20, seven multipliers 21 _{1 to} 21 ₇ and 7
Each of the delay devices 22 _{1 to} 22 ₇ is configured. 6th II
FIG. 5 shows an example of the configuration of the R-type filter 20. The 6th-order IIR type filter 20 is also a well-known filter in which a configuration called a standard type of the IIR system is connected in series.
The multipliers 21 _{1 to} 21 ₇ amplify the signals from the 6th-order IIR filter 20 in accordance with the multiplication coefficients. The outputs of the multipliers 21 _{1 to} 21 ₇ are delay devices 22 ₁ to 2 2, respectively.
It is supplied to the 2 _7. Each of the delay devices 22 _{1 to} 22 ₇ delays the signals from each of the multipliers 21 _{1 to} 21 ₇ by a time corresponding to the delay coefficient and supplies the delayed signals to the adder 23. Adder 23
Adds the signals from the respective delay devices 22 _{1 to} 22 ₇ . The output of the adder 23 is supplied to the adder 24.

The adder 24 adds the direct sound generation system signal from the delay unit 12 and the reflected sound generation system signal from the adder 23. As a result, the direct sound and the reflected sound are superimposed, and the characteristics of the first composite sound signal or the second head acoustic transfer function to which the characteristics of the first head acoustic transfer function are added to the input signal are added. The generated second composite sound signal is generated.

FIG. 6 is a block diagram showing the structure of the difference signal generating means. The difference signal generating means is composed of a subtractor 30 and a filter 31. The subtractor 30 subtracts the second direct sound signal from the first direct sound signal from the first signal processing means. The output of the subtractor 30 is supplied to the filter 31. As the filter 31, a first-order low-pass filter with a cutoff frequency of 600 Hz can be used. The output of the filter 31 is supplied to the cancellation signal generating means as a difference signal.

FIG. 7 is a block diagram showing the structure of the cancellation signal generating means. The cancellation signal generating means includes a delay device 40 and a delay device 41. The delay device 40 is
The difference signal from the difference signal generating means is delayed by the time corresponding to the delay coefficient. The output of the delay device 40 is supplied to the first signal generating means (see FIG. 1) as a first cancellation signal. Further, the delay device 41 delays the difference signal from the difference signal generating means by a time corresponding to the delay coefficient. The output of the delay device 41 is supplied to the second signal generating means (see FIG. 1) as the second cancellation signal.

FIG. 8 is a block diagram showing the structure of the first signal generating means. The first signal generating means is composed of a multiplier 50, a multiplier 51 and an adder 52. The multiplier 50 amplifies the first composite sound signal from the first signal processing means according to the multiplication coefficient. The output of the multiplier 50 is supplied to one input terminal of the adder 52. The multiplier 51 amplifies the first cancellation signal from the cancellation signal generation means according to the multiplication coefficient. The output of the multiplier 51 is supplied to the other input terminal of the adder 52. The adder 52 adds the signal from the multiplier 50 and the signal from the multiplier 51. The signal of the adder 52 is output to the outside of the sound image control device as a signal for the first channel, that is, a signal for the left channel.

FIG. 9 is a block diagram showing the structure of the second signal generating means. The second signal generating means is composed of a multiplier 60, a multiplier 61 and a subtractor 62. The multiplier 60 amplifies the second composite sound signal from the second signal processing means according to the multiplication coefficient. The output of the multiplier 60 is supplied to one input terminal of the subtractor 62. The multiplier 61 amplifies the second cancellation signal from the cancellation signal generation means according to the multiplication coefficient. The output of the multiplier 61 is supplied to the other input terminal of the subtractor 62. The subtractor 62 subtracts the signal from the multiplier 61 from the signal from the multiplier 60. The signal of the subtracter 62 is output to the outside of the sound image control device as a second channel signal, that is, a right channel signal.

Next, the operation of the sound image control device according to the second embodiment will be described. FIG. 10 shows how the head acoustic transfer function is measured using a dummy head microphone. The measurement is preferably performed in a room where some reflection occurs. The impulse emitted from the speaker is picked up by the dummy head microphone. In this case, the head acoustic transfer function is measured by generating impulses from all directions and distances centering on the dummy head.

FIG. 11 shows an example of the waveform of the head impulse response of the head acoustic transfer function thus measured.
In FIG. 11, the direct part is the head impulse response in the range from 4.5 ms after the impulse is input,
The reflector is a head impulse response ranging from 4.5 to 21 ms. It should be noted that these time values are values based on actual measurement and differ depending on the measurement environment.

Next, a method of equalizing the head acoustic transfer function measured as described above by an IIR type filter will be described with reference to FIGS. 12 and 13.

First, from the waveform (original waveform) of the head impulse response of the left and right direct parts, as shown in FIG. I
The IR filter 10 is used for approximation. The waveform of this approximated head impulse response is shown in FIG. The reason why the 8th-order IIR type filter is used as a filter is that it has been confirmed by experiments that the approximation by this filter is the most efficient in terms of the processing amount of the DSP. In addition,
The filter is not limited to the 8th-order IIR type filter, and any filter can be used according to the required performance, price, and the like.

Next, in order to form the binaural time difference between the right and left direct parts, a predetermined delay coefficient is given to each delay device 12 of the first signal processing means and the second signal processing means. As a result, each delay device 12 delays each signal from the eighth-order IIR filter 10 according to the delay coefficient and outputs the delayed signal. As described above, the direct part is equalized as shown in FIG.

Next, the reflection part is equivalent. That is, FIG.
As shown in (A), a representative portion is extracted from the waveform (original waveform) of the head impulse response of the picked-up left and right reflecting portions. Then, from the extracted waveform of the head impulse response, the head acoustic transfer function of the left and right reflected sounds is calculated by the 6th order I
The IR filter 20 is used for approximation. The waveform of this approximated head impulse response is shown in FIG. FIG.
In FIG. 3 (B), a scale different from the other figures is used, and an enlarged waveform is shown. The reason why the sixth-order IIR type filter is used as the filter is that it has been confirmed by experiments that the approximation by this filter is the most efficient in terms of the throughput of the DSP. The filter is not limited to the 6th-order IIR type filter, and any filter can be used according to the required performance, price, and the like.

On the other hand, as shown in FIG. 13C, seven taps are selected from a portion having a large amplitude in the waveform (original waveform) of the head impulse response of the picked-up left and right reflecting portions. . The number of taps is not limited to seven. Then, as shown in FIG. 13D, these taps and the waveform of the head impulse response approximated by the 6th-order IIR filter are combined, and the reflection part is equalized. The amplitude of the waveform at each tap is determined by the multiplication coefficient given to the multipliers 21 _{1 to} 21 ₇ . Further, the temporal position of each tap is determined by the delay coefficient given to the delay devices 22 _{1 to} 22 ₇ . Then, the signals from the delay devices 22 _{1 to} 22 ₇ are added by the adder 23.

Finally, the head impulse response approximating the direct part and the head impulse response approximating the reflecting part are combined, and the head acoustic transfer function is equalized as shown in FIG. 13 (E). Be seen.

Next, the localization of the sound image and the movement of the sound image when listening to the speaker using the sound image control apparatus of the first embodiment will be described. As shown in FIG. 14, assuming that the binaural path difference is y, the head diameter is x, and the speaker opening angle is α, the binaural path difference y is approximated by the following equation.

[0058]

## EQU00001 ## y.apprxeq.sin .alpha .... Equation (1) Note that the speaker opening angle .alpha. Is an angle formed by the front direction of the listener and the line connecting the center of the head and one of the speakers.

Now, assuming that the head diameter is 22 cm and the speaker opening angle is 15 °, the binaural path difference is 5.69 cm. When the sound velocity is 340 m / s, the arrival time difference of 5.69 cm is about 167 μs. If the sampling frequency is 48 kHz, the time difference corresponds to 8 sample points. Therefore, if the sounds output from the left and right speakers are to reach the right ear at the same time, the sound output from the right speaker may be delayed by 8 sample points. If the sounds output from the left and right speakers are reversed in phase and the output from the right speaker is delayed by 8 sample points,
Sounds cancel each other out in the right ear. Therefore, a space where the sound image is easily localized is formed on the left side.

Therefore, when it is desired to localize the sound image laterally, if the negative phase signal output from the speaker on the opposite side is delayed by 8 sample points, the localization of the sound image becomes closer to the lateral side. The amount of delay is reduced as it goes to the front,
If the delay amount is set to zero in front of the sound image, the sound image is perceived farther. Further, the sound image can be smoothly moved by gradually changing the delay amount.

FIG. 15A shows the relationship between the angle and the delay amount in the cancellation signal generating means. As shown in FIG. 15B, when the front direction is 0 °, the left direction is 90 °, the rear direction is 180 °, and the right direction is 270 °, the delay amounts of the delay units 40 and 41 in FIG. It becomes like FIG. 15 (A).
For example, if the sound image is to be localized in the left direction (90 °), the delay amount of the left channel delay device 40 is set to zero,
By setting the delay amount of the delay device 41 for the right channel to “8”, signals of opposite phases cancel each other around the right ear, and a space where a sound image is easily localized is formed on the left side. If a signal with the characteristics of the left head acoustic transfer function is added to this,
The sound image is clearly localized on the left side.

In the example shown in FIG. 15A, the delay amount with respect to the sound image position (angle) of each channel is linearly changed, but it may not be linearly changed. For example, it can be configured to change with various characteristics such as a trigonometric function, an exponential function, and the like.

(Embodiment 2) A sound image control apparatus according to Embodiment 2 of the present invention comprises two series of functional blocks equivalent to those of the sound image control apparatus according to Embodiment 1 described above.
Then, the first weighting means is added to the first series of functional blocks, and the second weighting means is added to the second series of functional blocks. Therefore, it is possible to localize one sound image by the first functional block and localize another sound image by the second functional block.

FIG. 2 is a block diagram showing the configuration of the sound image control apparatus according to the second aspect of the present invention. The first weighting means, the second weighting means, and the first to the fourth shown in FIG.
Each block of the signal processing means, the difference signal generation means, the cancellation signal generation means, the first signal generation means, and the second signal generation means is assumed to be realized by a DSP.

Also in the second embodiment, the first channel signal is the left channel signal and the second channel signal is the right channel signal. Therefore, the first composite sound signal and the first direct sound signal generated by the first signal processing means are the left composite sound signal and the left direct sound signal, respectively, and are generated by the third signal processing means. The third composite sound signal and the third direct sound signal are the left composite sound signal and the left direct sound signal, respectively. Similarly, the second composite sound signal and the second direct sound signal generated by the second signal processing means are the right composite sound signal and the right direct sound signal, respectively, and are generated by the second signal processing means. The generated second composite sound signal and second direct sound signal are the right composite sound signal and the right direct sound signal, respectively. The first cancellation signal generated by the cancellation signal generation means is a left cancellation signal, and the second cancellation signal is a right cancellation signal.

The first weighting means and the second weighting means shown in FIG. 2 can be respectively configured by a first multiplier and a second multiplier (neither is shown). Here, the multiplication coefficient given to the _first multiplier is K ₁ , the multiplication coefficient given to the _second multiplier is K ₂ , and the multiplication coefficients K ₁ and K _{2 are given.}
Can take a value in the range of "0-1". These multiplication coefficients K ₁ and K ₂ are determined so as to satisfy the following expression and are given to the first and second multipliers.

[0067]

[Formula 2] K ₁ + K ₂ = 1 ... Equation (2)

Therefore, when operating with only the first series of functional blocks, multiplication coefficients K ₁ = 1 and K ₂ = 0 are given. On the contrary, in the case of operating only the second series functional blocks, multiplication coefficients K ₁ = 0 and K ₂ = 1 are given. And
When operating both at the same time, "0 <K ₁ , K ₂ <1"
Multiplication factors in the range are given. The signal weighted by the first multiplier is supplied to the first and second signal processing means, and the signal weighted by the second multiplier is supplied to the third and fourth signal processing means. .

The configurations of the first signal processing means to the fourth signal processing means are the same as those of the signal processing means of the first embodiment.
It has already been described with reference to the block diagram of FIG. However, the coefficients given to each element (filter, multiplier, delay device) configuring each of these means are different. That is, the first signal processing means and the third signal processing means are provided with a coefficient for approximating the first head acoustic transfer function, and the second processing means and the fourth processing means are provided with the second signal processing means. Coefficients for approximating the head acoustic transfer function of are given.

FIG. 16 is a block diagram showing the structure of the difference signal generating means. The difference signal generating means includes an adder 70, an adder 71, a subtractor 72, and a filter 73. The adder 70 adds the first direct sound signal from the first signal processing means and the third direct sound signal from the third signal processing means. The output of the adder 70 is supplied to one input terminal of the subtractor 72. The adder 71 adds the second direct sound signal from the second signal processing means and the fourth direct sound signal from the fourth signal processing means. This adder 7
The output of 1 is supplied to the other input terminal of the subtractor 72. The subtractor 72 adds the output signal of the adder 70 to the adder 7
The output signal of 1 is subtracted. The output of the subtractor 72 is supplied to the filter 73. As the filter 73, the same filter as in the first embodiment can be used.
The output of the filter 31 is supplied to the cancellation signal generating means as a difference signal.

As the cancellation signal generating means, the same one as described in the first embodiment is used. The details of the cancellation signal generating means have already been described with reference to FIG. The first cancellation signal from the cancellation signal generation means is supplied to the first signal generation means (see FIG. 1), and the second cancellation signal is supplied to the second signal generation means (see FIG. 1).

The first signal generating means is, as shown in FIG. 17, an adder 80, a multiplier 81, a multiplier 82 and an adder 8.
3. The adder 80 adds the first composite sound signal from the first signal processing means and the third composite sound signal from the third signal processing means. The output of the adder 80 is supplied to the multiplier 81. The multiplier 81 is the adder 8
The signal from 0 is amplified according to the multiplication coefficient. The output of the multiplier 81 is supplied to one input terminal of the adder 83. The multiplier 82 amplifies the first cancellation signal from the cancellation signal generation means according to the multiplication coefficient. The output of the multiplier 82 is supplied to the other input terminal of the adder 83. The adder 83 receives the signal from the multiplier 81 and the multiplier 82.
The signal from is added. The signal of the adder 83 is output to the outside of the sound image control device as a signal for the first channel, that is, a signal for the left channel.

The second signal generating means is, as shown in FIG. 18, an adder 90, a multiplier 91, a multiplier 92 and a subtractor 9
3. The adder 90 adds the second composite sound signal from the second signal processing means and the fourth composite sound signal from the fourth signal processing means. The output of the adder 90 is supplied to the multiplier 91. The multiplier 91 is the adder 9
The signal from 0 is amplified according to the multiplication coefficient. The output of the multiplier 91 is supplied to one input terminal of the subtractor 93. The multiplier 92 amplifies the second cancellation signal from the cancellation signal generation means according to the multiplication coefficient. The output of the multiplier 92 is supplied to the other input terminal of the subtractor 93. The subtractor 93 calculates the multiplier 9 from the signal from the multiplier 91.
Subtract the signal from 2. The signal of the subtractor 93 is output to the outside of the sound image control device as a second channel signal, that is, a right channel signal.

Next, the operation of the sound image control device according to the second embodiment will be described. The sound image control device according to the second embodiment is provided with two series of functional blocks, and the operation of each series of functional blocks is the same as that of the sound image control device according to the first embodiment.

According to the sound image control apparatus of the second embodiment, one sound image can be localized by the first functional block, and the other sound image can be localized by the second functional block. it can.

Now, the first one forming the first weighting step
If the multiplication coefficient K ₁ given to the multiplier of _{1 is set} to "1" and the multiplication coefficient given to the second multiplier constituting the second weighting means is set to "0", the functional block of the second series does not exist. And, like the sound image control apparatus according to the first embodiment, one sound image is localized only by the functional blocks of the first series. From this state, when the multiplication coefficient K ₁ is gradually decreased and the multiplication coefficient K ₂ is gradually increased, the sound image formed by the first series of functional blocks gradually decreases, and the second series of functional blocks is gradually reduced. The sound image formed by is gradually increased. Then, the multiplication coefficient K given to the first multiplier
_{When 1} becomes “0” and the multiplication coefficient K ₂ given to the second multiplier becomes “1”, it is equal to the state in which there is no functional block of the first series, and the sound image control apparatus according to the first embodiment described above. Similarly, one sound image is localized only by the second series of functional blocks.

Therefore, when the sound image is moved from a certain position to another position, the multiplication coefficient K ₁ of the first multiplier is gradually increased and the multiplication coefficient K ₂ of the _second multiplier is gradually decreased. By performing the above or vice versa, it is possible to suppress the generation of noise accompanying the replacement of the coefficients of the sound image control device and to smoothly move the sound image. Further, since the generation of noise can be suppressed even if the sound image is largely moved, it is not necessary to prepare the coefficients corresponding to many sound image positions as in the conventional case, and the amount of the coefficient to be prepared in advance can be reduced.

FIG. 19 is a top view of the present sound image control device. An operation panel 100 and a display 110 are provided on the upper surface of the sound image control device. The operation panel 100 is provided with an angle knob 101, a vertical knob 102, a perspective knob 103, and other switches.

The angle knob 101 is used for designating the position of the sound image by the angle when the front of the listener is 0 °, for example. As the angle knob 101, for example, a rotary encoder or an operator equivalent thereto can be used. A joystick may be used instead of the angle knob 101. Upper and lower knobs 102
Is used to specify the vertical position of the sound image. As the upper and lower knobs 102, a slide volume control, a rotary volume control, and an operator having a function equivalent to these can be used. Also, the perspective knob 1
03 is used to specify the distance from the listener to the sound image. As the far and near knob 103, a slide volume control, a rotary volume control, and an operator having a function equivalent to these can be used. The sound image positions in all directions can be specified by the above three knobs 101 to 103.

Further, the display 11 is provided on the upper surface of the sound image control device.
0 is provided. The display device 110 displays the current sound image position information, for example, the angle, the vertical position, the distance, etc., in the form of numerical values or pictures.

Further, the present sound image control device is provided with an audio input terminal. The audio signal is taken into the sound image control device via the audio input terminal. Moreover, a headphone output terminal and a line output terminal are provided as output terminals. A left channel signal (L) and a right channel signal (R) are output from these terminals. As a result, headphones and speakers can be heard.

Further, the sound image control device may be provided with an external input terminal so that the sound image position information is inputted from an external device such as a MIDI device or a computer. Further, a line input terminal may be provided so as to superimpose an audio signal of a predetermined music from an external stereo system with a signal whose sound image position is controlled, and output the signal.

FIG. 20 is a block diagram showing the configuration of an electric circuit of the present sound image control apparatus. The audio signal input from the outside is converted into digital data by the A / D converter 400 and sent to the DSP 500. The DSP 500 processes the received digital data according to the coefficient sent from the CPU 200, and generates the data to which the sound image localization as described above is added. The data (left channel signal and right channel signal) generated by the DSP 500 is sent to the D / A converter 600. The D / A converter 600 converts the received digital data into an analog signal. The analog headphone output signal from the D / A converter 600 is output to the outside from the headphone output terminal. The analog signal from the D / A converter 600 is amplified by the amplifier 700 and then output as a line output signal from the line output terminal to the outside.

On the other hand, the coefficient memory 300 stores coefficients (filter coefficient, multiplication coefficient, delay coefficient, etc.) corresponding to a plurality of sound image positions. The coefficient memory 300 can be composed of, for example, a ROM. Further, the sound image position information set by the knobs 101 to 103 on the operation panel 100 is converted into digital data and sent to the CPU 200. The CPU 200 reads the coefficient corresponding to this digital data from the coefficient memory 300, and the DSP 500
Send to As a result, the DSP 500 performs the processing for localizing the sound image in the audio input signal by the above-described operation, and outputs it to the outside.

Each knob 1 on the operation panel 100 during sounding
When 01 to 103 are operated, a process of gradually moving the sound image position is performed by panning the newly specified sound image position and the sound image position specified immediately before. More specifically, the multiplication coefficient K ₁ given to the first multiplier constituting the first weighting means and the multiplication coefficient K ₂ given to the second multiplier constituting the second weighting means are described above. The sound image position is moved by gradually changing the sound image position. As a result, it is possible to suppress the generation of noise due to a large movement of the sound image position (a large change in the coefficient).

When the sound image is moved, noise is not generated unless the sound image position is largely moved, that is, the coefficient is not largely changed. Therefore, the number of sound image positions that can be localized (the number of coefficients stored in the coefficient memory 300) is increased, and when moving from the current sound image position to a new sound image position, the sound image positions that can be localized in the middle are located. If the sound image is moved sequentially, the above panning process is unnecessary. In this case, it is not necessary to provide two series of functional blocks as in the second embodiment,
The sound image control device according to the first embodiment described above can be used. According to this configuration, the processing amount of the DSP 500 becomes about half.

[0087]

As described in detail above, according to the present invention,
It is possible to provide a sound image control device and a sound image control method capable of localizing a sound image at an arbitrary position including a position distant from a listener by reproducing two channels of a speaker, and also obtaining an out-of-head feeling even when listening through headphones. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a sound image control device according to a first aspect of the present invention.

FIG. 2 is a block diagram showing a configuration of a sound image control device according to a second aspect of the present invention.

FIG. 3 is a block diagram showing a detailed configuration of first to fourth signal processing means of the present invention.

FIG. 4 is a block diagram showing an example of an 8th-order IIR type filter used in Embodiments 1 and 2 of the present invention.

FIG. 5 is a block diagram showing an example of a 6th-order IIR filter used in the first and second embodiments of the present invention.

FIG. 6 is a block diagram showing a configuration of difference signal generating means according to the first embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a cancellation signal generation means according to the first and second embodiments of the present invention.

FIG. 8 is a block diagram showing a configuration of a first signal generating means according to the first embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of a first signal generating means according to the first embodiment of the present invention.

FIG. 10 is an explanatory diagram showing how a head acoustic transfer function is measured using a dummy head microphone in the first and second embodiments of the present invention.

FIG. 11 is a diagram showing an example of the waveform of the head impulse response of the measured head acoustic transfer function in the first and second embodiments of the present invention.

FIG. 12 is a diagram for explaining a method of equalizing a head acoustic transfer function by an IIR type filter in the first and second embodiments of the present invention.

FIG. 13 is a diagram for explaining a method of equalizing a head acoustic transfer function with an IIR filter in the first and second embodiments of the present invention.

FIG. 14 is a diagram for explaining localization of a sound image and movement of the sound image when listening to a speaker in the first and second embodiments of the present invention.

FIG. 15 is a diagram showing a relationship between an angle and a delay amount in the cancellation signal generating means in the first and second embodiments of the present invention.

FIG. 16 is a block diagram showing a configuration of difference signal generation means according to a second embodiment of the present invention.

FIG. 17 is a block diagram showing a configuration of a first signal generating means according to the second embodiment of the present invention.

FIG. 18 is a block diagram showing a configuration of a second signal generating means according to the second embodiment of the present invention.

FIG. 19 is a diagram showing an appearance of a sound image control device according to a second embodiment of the present invention.

FIG. 20 is a block diagram showing an electric circuit of a sound image control device according to a second embodiment of the present invention.

[Explanation of symbols]

10 8th-order IIR type filter 20 6th-order IIR type filter 11, 21 _{1 to} 21 ₇ , 50, 51 Multiplier 60, 61, 81, 82, 91, 92 Multiplier 12, 22 _{1 to} 22 ₇ , 40, 41 Delay device 23, 24, 52, 70, 71, 80, 83, 90
Adder 30, 62, 72, 93 Subtractor 23, 73 First-order low-pass filter 100 Operation panel 101 Angle knob 102 Up / down knob 103 Perspective knob 110 Display 200 CPU 300 Coefficient memory 400 A / D converter 500 DSP 600 D / A Converter 700 Amplifier

Claims (4)

[Claims] 1. A first direct sound signal corresponding to a direct sound, and a first sound corresponding to a composite sound of a direct sound and a reflected sound, by processing an input signal using a first head acoustic transfer function. And a second direct sound signal corresponding to a direct sound by processing the input signal using a second head acoustic transfer function, Second signal processing means for generating a second composite sound signal corresponding to a composite sound of the direct sound and the reflected sound; and a second signal processing means for generating a second composite sound signal from the first direct sound signal from the first signal processing means.
Difference signal generating means for generating a difference signal by subtracting the second direct sound signal from the signal processing means, and a first for delaying the difference signal from the difference signal generating means to control the cancellation position. Canceling signal generating means for generating the canceling signal and the second canceling signal, the first composite sound signal from the first signal processing means, and the first canceling signal from the canceling signal generating means are added. Then, the second cancellation signal from the cancellation signal generation means is subtracted from the first signal generation means for generating the signal for the first channel and the second composite sound signal from the second signal processing means. Then, the sound image control device is provided with a second signal generating means for generating a signal for the second channel. 2. A direct sound is obtained by processing first weighting means for first weighting an input signal, and processing the signal from the first weighting means using a first head acoustic transfer function. A first signal processing means for generating a corresponding first direct sound signal and a first composite sound signal corresponding to a composite sound of the direct sound and the reflected sound; and a signal from the first weighting means. A second direct sound signal corresponding to the direct sound and a second composite sound signal corresponding to the composite sound of the direct sound and the reflected sound are generated by processing using the second head acoustic transfer function. Second signal processing means for performing the second weighting on the input signal, and processing the signal from the second weighting means using the first head acoustic transfer function According to the third direct sound signal corresponding to the direct sound, and a composite sound of the direct sound and the reflected sound. And a third signal processing means for generating a third composite sound signal corresponding to, and a signal from the second weighting means are processed by using a second head acoustic transfer function to obtain a direct sound. Fourth signal processing means for generating a corresponding fourth direct sound signal and a fourth composite sound signal corresponding to a composite sound of the direct sound and the reflected sound; and a fourth signal processing means from the first signal processing means. 1 direct sound signal and the third
The second direct sound signal from the second signal processing means and the fourth direct sound signal from the fourth signal processing means from the addition result with the third direct sound signal from the signal processing means Difference signal generating means for generating a difference signal by subtracting the addition result of, and a first canceling signal and a second canceling signal for delaying the difference signal from the difference signal generating means to control the canceling position. Canceling signal generating means for generating, a first synthesized sound signal from the first signal processing means, and the third
First signal generation means for adding the third synthesized sound signal from the signal processing means and the first cancellation signal from the cancellation signal generation means to generate a signal for the first channel, and the second signal generation means. The second synthesized sound signal from the signal processing means of
Second signal generating means for subtracting the second canceling signal from the canceling signal generating means from the addition result with the fourth synthesized sound signal from the signal processing means to generate the second channel signal, And a sound image control device. 3. A first direct sound signal corresponding to a direct sound, and a first sound corresponding to a composite sound of a direct sound and a reflected sound, by processing an input signal using a first head acoustic transfer function. 1 composite sound signal is generated and the input signal is processed by using the second head acoustic transfer function, whereby the second direct sound signal corresponding to the direct sound and the direct sound and the reflected sound are generated. A second composite sound signal corresponding to the composite sound is generated, a difference signal is generated by subtracting the second direct sound signal from the first direct sound signal, and the difference signal is delayed to cancel the position. Generate a first cancellation signal and a second cancellation signal for controlling, and add the first composite sound signal and the first cancellation signal to generate a signal for the first channel. , The second canceling signal is subtracted from the second composite sound signal to obtain the second channel signal. Sound image control method characterized by generating a. 4. A first direct signal corresponding to a direct sound by first weighting an input signal and processing the first weighted signal with a first head related acoustic transfer function. A sound signal and a first composite sound signal corresponding to a composite sound of a direct sound and a reflected sound are generated, and the first weighted signal is processed using a second head acoustic transfer function. As a result, a second direct sound signal corresponding to the direct sound and a second composite sound signal corresponding to the composite sound of the direct sound and the reflected sound are generated, and the input signal is second weighted, By processing the second weighted signal using the first head acoustic transfer function, a third direct sound signal corresponding to the direct sound and a composite sound of the direct sound and the reflected sound are processed. And a third composite sound signal for generating the second weighted signal and outputting the second weighted signal to the second head acoustic transmission. By processing using a function, a fourth direct sound signal corresponding to the direct sound and a fourth composite sound signal corresponding to the composite sound of the direct sound and the reflected sound are generated, and the first direct sound signal is generated. A difference signal is generated by subtracting the addition result of the second direct sound signal and the fourth direct sound signal from the addition result of the sound signal and the third direct sound signal, and the difference signal is generated. A first cancellation signal and a second cancellation signal for delaying to control the cancellation position are generated, and the first synthesized sound signal, the third synthesized sound signal and the first cancellation signal are added. , A signal for the first channel is generated, and the second canceling signal is subtracted from the addition result of the second synthesized sound signal and the fourth synthesized sound signal. A sound image control method characterized by generating.