The present disclosure relates to an audio signal processing device, an audio signal processing method, and a computer program.
There is a case where, when a listener wears headphones on the head of the listener to hear sound reproduced signals with both ears of the listener, audio signals reproduced by the headphones are normal audio signals that are provided to speakers located at the right and left in front of the listener. In such a case, it is known that a phenomenon so-called inside-the-head sound localization occurs in which a sound image reproduced by the headphones is trapped inside the head of the listener.
As techniques that solve this problem of the inside-the-head sound localization phenomenon, for example, Patent Literature 1 and Patent Literature 2 disclose a technique called virtual sound image localization. This virtual sound image localization causes headphones or the like to perform reproduction as if sound sources, for example, speakers are present at presupposed positions such as the right and left positions in front of a listener (to virtually localize the sound image at the positions).
In the case of multi-channels including three or more channels, as with a case of two channels, speakers are disposed at virtual sound image localization positions of the respective channels, and head-related transfer functions for the respective channels are measured by, for example, reproducing impulses. Then, the impulse responses of the head-related transfer functions obtained by the measurement may be convolved with audio signals to be provided to drivers for 2-channel sound reproduction of the right and left headphones.
Now, recently, multichannel surround sound systems such as 5.1 channel, 7.1 channel, and 9.1 channel, have been employed in sound reproduction or the like accompanying the reproduction of a video recorded in an optical disk. Also in the case where audio signals in this multichannel surround sound system are subjected to the sound reproduction by 2-channel headphones, the use of the above-described method of virtual sound image localization to perform sound image localization (virtual sound image localization) in conformity with each channel is proposed (e.g., Patent Literature 3).
Patent Literature 1: WO 95/013690
Patent Literature 2: JP 03-214897A
Patent Literature 3: JP 2011-009842A
In the techniques for subjecting audio signals in the multichannel surround sound system to sound reproduction using head-related transfer functions by 2-channel headphones, only by simulating a supposed environment of the speakers, it is difficult to reproduce sound quality and a sound field as they are at the time of hearing with speakers actually disposed. At the time of hearing with headphones, the headphones are firmly fixed on the head of a listener and sound is output from the vicinities of the ears of the listener, but at the time of hearing sound from speakers, the head of a listener is not fixed but moves slightly. Therefore, at the time of hearing sound from speakers, the distances from the speakers to the ears of a listener and the angles (directions) toward the speakers viewed from the listener are not constant.
If reverb components are added more than necessary to reproduce a wide sound field in an attempt to simulate a supposed environment of speakers, the sound reverberates excessively, or out-of-head sound localization is not achieved as much as a supposed distance from the speakers.
Thus, the present disclosure provides a novel and improved audio signal processing device, audio signal processing method, and computer program that can reproduce, at the time of reproducing audio signals in a multichannel surround sound system with 2-channel audio signals, sound quality and a sound field at the time of hearing with speakers actually disposed.
According to the present disclosure, there is provided an audio signal processing device including a signal processing section that changes, at a time of generating and outputting 2-channel audio signals to be subjected to sound reproduction by two electroacoustic transducing means located at positions in the vicinities of both ears of a listener, from audio signals of a plurality of and more than two channels, virtual sound image localization positions on a circle around the listener, across the virtual sound image localization positions, the virtual sound image localization position that is supposed for each of the plurality of channels of audio signals provided on the circle.
According to the present disclosure, there is provided an audio signal processing method, including a step of changing, at a time of generating and outputting 2-channel audio signals to be subjected to sound reproduction by two electroacoustic transducing means located at positions in the vicinities of both ears of a listener, from audio signals of a plurality of and more than two channels, virtual sound image localization positions on a circle around the listener, across the virtual sound image localization positions, the virtual sound image localization position that is supposed for each of the plurality of channels of audio signals provided on the circle.
According to the present disclosure, there is provided a computer program that causes a computer to execute a step of changing, at a time of generating and outputting 2-channel audio signals to be subjected to sound reproduction by two electroacoustic transducing means located at positions in the vicinities of both ears of a listener, from audio signals of a plurality of and more than two channels, virtual sound image localization positions on a circle around the listener, across the virtual sound image localization positions, the virtual sound image localization position that is supposed for each of the plurality of channels of audio signals provided on the circle.
As described above, according to the present disclosure, it is possible to provide a novel and improved audio signal processing device, audio signal processing method, and computer program that can reproduce, at the time of reproducing audio signals in a multichannel surround sound system with 2-channel audio signals, sound quality and a sound field at the time of hearing with speakers actually disposed.
Hereinafter, a preferred embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. Note that, in the present specification and the drawings, elements having substantially the same functions and configurations are denoted by the same reference signs, and redundant explanations will be omitted.
Note that the description will be made in the following order.
<1. Embodiment of the Present Disclosure>
[Example for Speaker Arrangement in 7.1 Channel Multichannel Surround Sound]
[Configuration Example of Audio Signal Processing Device]
[Operation Example of Audio Signal Processing Device]
<2. Conclusion>
[Configuration Example of Audio Signal Processing Device]
First, an example of speaker arrangement for multichannel surround sound will be described with reference to the drawings.
The example of speaker arrangement of the 7.1 channel multichannel surround sound compliant with ITU-R is defined, as illustrated in
In
Then, two speaker positions LS and LB, and two speaker positions RS and RB are set on the right and left sides of the front position C of the listener Pn within a range from 60 degrees to 150 degrees. These speaker positions LS and LB, and RS and RB are set at positions symmetrical with respect to the listener. The speaker positions LS and RS are the speaker positions of a left side channel and a right side channel, and the speaker positions LB and RB are the speaker positions of a left rear channel and a right rear channel.
In this example of a sound reproduction system, headphones having headphone drivers disposed one by one for each of the headphones for the right and left ears of the listener Pn, are used as over ear headphones.
In this embodiment, when multichannel surround sound audio signals in 7.1 channels are subjected to sound reproduction by the over ear headphones of this example, the sound reproduction is performed considering the directions toward the speaker positions C, LF, RF, LS, RS, LB, and RB in
Note that the following description will be made on the basis of the 7.1-channel multichannel surround sound illustrated in
The example of speaker arrangement in 7.1-channel multichannel surround sound is described above with reference to
[Configuration Example of Audio Signal Processing Device]
The example illustrated in these
Note that, in these
As illustrated in
The audio signals from these level adjusting sections 71LF, 71LS, 71RF, 71RS, 71LB, 71RB, 71C, and 71LFE are amplified by predetermined amounts by the amplifier 72LF, 72LS, 72RF, 72RS, 72LB, 72RB, 72C, and 72LFE and thereafter provided to A/D converters 73LF, 73LS, 73RF, 73RS, 73LB, 73RB, 73C, and 73LFE, respectively, to be converted into digital audio signals.
The digital audio signals from the A/D converters 73LF, 73LS, 73RF, 73RS, 73LB, 73RB, 73C, and 73LFE are subjected to signal processing, to be described hereafter, by a signal processing section 100 before provided to head-related transfer function convolution processing sections 74LF, 74LS, 74RF, 74RS, 74LB, 74RB, 74C, and 74LFE.
In each of the head-related transfer function convolution processing sections 74LF, 74LS, 74RF, 74RS, 74LB, 74RB, 74C, and 74LFE, in this example, a process of convolving direct waves and the reflected waves thereof with the head-related transfer function is performed using, for example, a convolution method disclosed in JP 2011-009842A.
In addition, in this example, each of the head-related transfer function convolution processing sections 74LF, 74LS, 74RF, 74RS, 74LB, 74RB, 74C, and 74LFE similarly performs the process of convolving the crosstalk components of the channels and the reflected waves thereof with the head-related transfer function using, for example, the convolution method disclosed in JP 2011-009842A.
Furthermore, in this example, it is assumed that the number of reflected waves to be processed by each of the head-related transfer function convolution processing sections 74LF, 74LS, 74RF, 74RS, 74LB, 74RB, 74C, and 74LFE is only one, for ease of description. It is needless to say that the number of reflected waves to be processed is not limited to such an example.
Output audio signals from the head-related transfer function convolution processing sections 74LF, 74LS, 74RF, 74RS, 74LB, 74RB, 74C, and 74LFE are provided to an addition processing section 75. The addition processing section 75 includes an adding section 75L for the left channel (hereafter, referred to as L adding section) and an adding section 75R for the right channel (hereafter, referred to as R adding section) of the 2-channel stereo headphones.
The L adding section 75L performs the addition of left channel components LF, LS, and LB that are essential and the reflected wave components thereof, the crosstalk components of right channel components RF, RS, and RB and the reflection components thereof, a center channel component C, and a low frequency effect channel component LFE.
Then, the L adding section 75L provides the result of the addition to, as illustrated in
The R adding section 75R performs the addition of the right channel components RF, RS, and RB that are essential and the reflected wave components thereof, the crosstalk components of the left channel components LF, LS, and LB and the reflection components thereof, the center channel component C, and the low frequency effect channel component LFE.
Then, the R adding section 75R provides the result of the addition to, as illustrated in
In this example, the center channel component C and the low frequency effect channel component LFE are provided to both the L adding section 75L and the R adding section 75R and added to both the left channel and the right channel. It is thereby possible to further improve the sense of localization of sound in the direction of the center channel, and to reproduce the low frequency audio component by the low frequency effect channel component LFE further improving the expanse thereof.
In the D/A converters 111L and 111R, in such a manner as described above, the synthesized audio signal SL for the left channel and the synthesized audio signal SR for the right channel that are convolved with the head-related transfer function, are converted into analog audio signals.
The analog audio signals from these D/A converters 111L and 111R are provided to current-voltage converting sections 112L and 112R, respectively, to be converted from current signals into voltage signals.
Then, the audio signals from the current-voltage converting sections 112L and 112R, which are converted into voltage signals, are subjected to level adjustment by level adjusting sections 113L and 113R, and thereafter provided to gain adjusting sections 114L and 114R to be subjected to gain adjustment.
Then, output audio signals from the gain adjusting sections 114L and 114R are amplified by amplifiers 115L and 115R, and thereafter output to output terminals 116L and 116R of the audio signal processing device of an embodiment. The audio signals lead to these output terminals 116L and 116R are provided to the headphone driver 120L for a light ear and the headphone driver 12R for a right ear, respectively, to be subjected to sound reproduction.
In the audio signal processing device 10, according to this example, headphone drivers can reproduce a sound field in the 7.1-channel multichannel surround sound through virtual sound image localization, with the headphone drivers 120L and 120R one by one for left and right ears.
Here, at the time of performing the sound reproduction on audio signals in a multichannel surround sound system by 2-channel headphones using the head-related transfer function, when the environment of the speakers that are supposed to be disposed as illustrated
Thus, in the present embodiment, by subjecting the 7.1-channel audio signals LF, LS, RF, RS, LB, RB, and C to signal processing in the signal processing section 100 illustrated in
By subjecting the 7.1-channel audio signals LF, LS, RF, RS, LB, RB, and C to the signal processing with the signal processing section 100 in a stage prior to the convolution with the head-related transfer function, the audio signal processing device 10 can perform convolution signal processing, and can improve the sound quality or expand the sound field of virtual surround sound after mixing the audio signals to be output to the 2-channel stereo headphones.
As described above, the configuration example of the audio signal processing device 10 according to an embodiment the present disclosure has been described with reference to
[Configuration Example of Signal Processing Section]
In the present embodiment, at the time of performing the signal processing with the signal processing section 100, in order to mix an audio signal with slight audio signals of other channels and to cause a sound image fluctuate slightly, two other audio signals that are positioned close to and at similar intervals from the audio signal are used.
For example, at the time of performing the above-described process on the signal of C, the signal processing section 100 uses the signals of L and R that are separated counterclockwise and clockwise by 30 degrees from the signal of C. In addition, at the time of performing the above-described process on the signal of L, the signal processing section 100 uses the signal of R clockwise away 60 degrees from the signal of L and the signal of LS counterclockwise away 90 degrees from the signal of L. Similarly, at the time of performing the above processing on the signal of R, the signal processing section 100 uses the signal of L counterclockwise away 60 degrees from the signal of R and the signal of RS clockwise away 90 degrees from the signal of R.
In addition, at the time of performing the above-described process on the signal of LS, the signal processing section 100 uses, for example, the signal of L 90 degrees clockwise away from the signal of LS and the signal of RS 120 degrees counterclockwise away from the signal of LS. Here, the signal processing section 100 uses the signal of RS 120 degrees counterclockwise away from the signal of LS rather than the signal of RB 90 degrees counterclockwise away from the signal of LS because the signal of RB does not exist in 5.1-channel multichannel surround sound. Similarly, at the time of performing the above-described process on the signal of RS, the signal processing section 100 uses the signal of R 90 degrees counterclockwise away from the signal of RS and the signal of LS 120 degrees clockwise away from the signal of RS. Also here, the signal processing section 100 uses the signal of LS 120 degrees clockwise away from the signal of RS rather than the signal of LB 90 degrees clockwise away from the signal of RS because the signal of LB does not exist in the 5.1-channel multichannel surround sound.
In addition, for example, at the time of performing the above-described process on the signal of LB, the signal processing section 100 uses the signal of LS 30 degrees clockwise away from the signal of LB and the signal of RB 60 degrees counterclockwise away from the signal of LB. Similarly, at the time of performing the above-described process on the signal of RB, the signal processing section 100 uses the signal of RS 30 degrees counterclockwise away from the signal of RB and the signal of LB 60 degrees clockwise away from the signal of RB.
In such a manner, the signal processing section 100 performs a process of slightly fluctuating the sound image on each audio signal using the above-described other two audio signals. By causing the sound image to fluctuate slightly, the audio signal processing device 10 can improve the sound quality and the sound field at the time of reproducing the audio signals in the multichannel surround sound system with the 2-channel audio signal.
Then, the signal processing section 100 synchronizes the fluctuation of the sound image across all the channels. In other words, the signal processing section 100 causes sound image localization positions to fluctuate so as to behave in the same way across all the channels. The audio signal processing device 10 can thereby reproduce the sound quality and the sound field at the time of hearing with speakers in the multichannel surround sound system actually disposed.
The amplifier 131a amplifies the signal of L by βf (1-2×αf). As the values of αf and βf, those which will be described hereafter are used. In addition, the amplifier 131b amplifies the signal of L by F_PanS*βf(αf*τ). Similarly, the amplifier 131c amplifies the signal of L by F_PanF*βf(αf*(1−τ)). Note that τ ranges between 0 and 1, being a value that varies on a predetermined cycle. In addition, as the values of F_PanS and F_PanF, those which will be described hereafter are used. Note that αf, βf, τ, F_PanS, and F_PanF are parameters to fluctuate the virtual sound image localization position with respect to the signal of L. This applies also to the following parameters.
The adder 131d adds the signal of LS to the signal of L amplified by the amplifier 131b and outputs the resultant signal. Similarly, the adder 131e adds the signal of RS to the signal of L amplified by the amplifier 131c and outputs the resultant signal. The signals amplified and added in such a manner by the signal processing section 100 are signals to be subjected to the processing of convolving the head-related transfer function.
The amplifier 132a amplifies the signal of C by βc(1-2×αc). As the values of αc and βc, those which will be described hereafter are used. In addition, the amplifier 132b amplifies the signal of C by βc(αc*τ). Similarly, the amplifier 132c amplifies the signal of C by βc(αc*(1−τ)).
The adder 132d adds the signal of L to the signal of C amplified by the amplifier 132b and outputs the resultant signal. Similarly, the adder 132e adds the signal of R to the signal of C amplified by the amplifier 132c and outputs the resultant signal. The signals amplified and added in such a manner by the signal processing section 100 are signals to be subjected to the processing of convolving the head-related transfer function.
The amplifier 133a amplifies the signal of R by βf(1-2×αf). As the values of αf and βf, those which will be described hereafter are used. In addition, the amplifier 133b amplifies the signal of R by F_PanF*βf(αf*τ). Similarly, the amplifier 133c amplifies the signal of R by F_PanS*βf(αf*(1−τ)).
The adder 133d adds the signal of L to the signal of R amplified by the amplifier 133b and outputs the resultant signal. Similarly, the adder 133e adds the signals RS to the signal of R amplified by the amplifier 133c and outputs the resultant signal. The signals amplified and added in such a manner by the signal processing section 100 are signals to be subjected to the processing of convolving the head-related transfer function.
The amplifier 134a amplifies the signal of LS by βs(1-2×αs). As the values of αs and βs, those which will be described hereafter are used. In addition, the amplifier 134b amplifies the signal of LS by S_PanS*βs(αs*τ). Similarly, the amplifier 134c amplifies the signal of LS by S_PanF*βs(αs*(1−τ)).
The adder 134d adds the signal of RS to the signal of LS amplified by the amplifier 134b and outputs the resultant signal. Similarly, the adder 134e adds the signal of L to the signals LS amplified by the amplifier 134c and outputs the resultant signal. The signals amplified and added in such a manner by the signal processing section 100 are signals to be subjected to the processing of convolving the head-related transfer function.
The amplifier 135a amplifies the signal of RS by βs(1-2×αs). As the values of αs and βs, those which will be described hereafter are used. In addition, the amplifier 135b amplifies the signal of RS by S_PanF*βs(αs*τ). Similarly, the amplifier 135c amplifies the signal of RS by S_PanS*βs(αs*(1−τ)).
The adder 135d adds the signal of R to the signal of RS amplified by the amplifier 135b and outputs the resultant signal. Similarly, the adder 135e adds the signal of LS to the signal of RS amplified by the amplifier 135c and outputs the resultant signal. The signals amplified and added in such a manner by the signal processing section 100 are signals to be subjected to the processing of convolving the head-related transfer function.
The amplifier 136a amplifies the signal of LB by βb(1-2×αb). As the values αb and βb, those which will be described hereafter are used. In addition, the amplifier 136b amplifies the signal of LB by B_PanS*βb(αb*τ). Similarly, the amplifier 136c amplifies the signal of LB by B_PanB*βb(αb*(1−τ)).
The adder 136d adds the signal of LS to the signal of LB amplified by amplifier 136b and outputs the resultant signal. Similarly, the adder 136e adds the signal of RB to the signal of LB amplified by the amplifier 136c and outputs the resultant signal. The signals amplified and added in such a manner by the signal processing section 100 are signals to be subjected to the processing of convolving the head-related transfer function.
The amplifier 137a amplifies the signal of RB by βb(1-2×αb). As the values of αb and βb, those which will be described hereafter are used. In addition, the amplifier 137b amplifies the signal of RB by B_PanB*βb(αb*τ). Similarly, the amplifier 137c amplifies the signal of RB by B_PanS*βb (αb*(1−τ)).
The adder 137d adds the signal of LB to the signal of RB amplified by the amplifier 137b and outputs the resultant signal. Similarly, the adder 137e adds the signal of RS to the signal of RB amplified by the amplifier 137c and outputs the resultant signal. The signals amplified and added in such a manner by the signal processing section 100 are signals to be subjected to the process of convolving the head-related transfer function.
As the above-described βc, αc, βf, αf, βs, αs, βb, and αb, the following values are used.
βc is approximately equal to 1.0
αc is approximately equal to 0.1
βf is approximately equal to 1.0
αf is approximately equal to 0.1
βs is approximately equal to 1.0
αs is approximately equal to 0.1*(60.0/210.0)
βb is approximately equal to 1.0
αb is approximately equal to 0.1*(60.0/90.0)
The above-described parameters are on the basis of the distribution of the signal of C, and defined on the assumption that the input signals fluctuate with the same sound image. With respect to each channel other than the signal of C, correction is made in conformity with the angles of speakers to which the channel is distributed.
In addition, the following parameters F_PanF, F_PanS, S_PanF, S_PanS, B_PanS, and B_PanB relate to signals that cannot be distributed with the same angle, the parameters used for performing angle correction including correction by hearing at the time of the distribution. How to distribute a signal that cannot be distributed with the same angle will be described hereafter.
F_Pan is approximately equal to 0.05
F_PanF=(1.0+F_Pan)
F_PanS=(1.0−F_Pan)
S_Pan=(F_Pan*(150.0/210.0))
S_PanF=(1.0+S_Pan)
S_PanS=(1.0−S_Pan)
B_Pan=(F_Pan*(150.0/90.0))
B_PanS=(1.0+B_Pan)
B_PanB=(1.0−B_Pan)
Here, those parameters shown with “is approximately equal to” are intended to indicate that values that are approximate to these may be used therefor. In practice, by varying these parameters a little from the above-described values, the audio signal processing device 10 can perform convolution signal processing, and can improve sound quality or expand the sound field of the virtual surround sound after mixing the audio signals to be output to the 2-channel stereo headphones.
The respective audio signals distributed in such a manner are distributed cyclically with τ ranging between 0 and 1 so as to have the same rotation in accordance with τ according to the same speaker arrangement. The cycle of this τ includes, for example, a fixed pattern and a pattern to randomly distribute. These patterns will be described hereafter.
As described above, the configuration example of the signal processing section 100 included in the audio signal processing device 10 according to an embodiment of the present disclosure has been described with reference to
[Operation Example of Audio Signal Processing Device]
First, in the signal processing section 100, with respect to the audio signal of each channel in the multichannel surround sound system, the center position of fluctuation is calculated (step S101). In the processing of step S101, after calculating the center position of fluctuation with respect to the audio signal of each channel, the signal processing section 100 subsequently calculates the width of fluctuation from the calculated center position of fluctuation with respect to the audio signal of each channel (step S102). Then, the signal processing section 100 causes the audio signal of each channel to fluctuate by the width of fluctuation calculated in step S102, before combining the audio signal of each channel with the audio signal of another channel (step S103).
At the time of causing the parameter τ to vary cyclically, the signal processing section 100 may cause the parameter τ to vary on a cycle close to a block size used in compressing audio data, which is hard for human ears to perceive. In addition, the signal processing section 100 may cause the parameter τ to vary on a random cycle. In addition, the signal processing section 100 may perform a control in such a manner as to cause the audio signal of each channel to fluctuate using the sum of multiplexed parameters t that are caused to vary on different cycles.
Here, the parameter τ used at the time of causing an audio signal to fluctuate will be described.
With respect to the pattern in which the parameter τ is caused to randomly vary as illustrated in
it is thus confirmed that the sound quality and the sound field tend to be further improved as n becomes greater.
Subsequently, an example of the width of fluctuation and angle correction of the audio signal of each channel are illustrated.
In addition, when the amounts of distribution are, as with the signal of C, 80% for R and a width of between 0 and 20% for L and RS, the sound image localization position by the signal of R′ is to fluctuate clockwise and counterclockwise within a range of 15 degrees across the sound image localization position by the signal of R′. With this, the degree of fluctuation is so large that the fluctuation does not become the same as that of the signal of C. Therefore, as with the signal of C, the degree of fluctuation of the sound image localization position by the signal of R is adjusted such that the degree of fluctuation is within a range of six degrees each to the right and right.
With this, the degree of fluctuation is adjusted into the width the same as that of the signal of C, but the sound image localization position by the signal of R deviates clockwise by six degrees from the original position, and it is thus necessary to align this sound image localization position with the original position.
To shift the position of U counterclockwise by six degrees, as illustrated in
By adjusting the angles in such a manner, it is possible to adjust the degree of fluctuation of the sound image localization position by the signal of R to six degrees each to the right and left, which is the same as the degree of fluctuation of the sound image localization position by the signal of C, in a state that the sound image localization position by the signal of R is aligned with the original position of R. These parameters for adjusting the degrees of fluctuation are βf, αf, F_PanF, and F_PanS out of the above-described parameters. By setting βf, αf, F_PanF, and F_PanS at the above-described values, it is possible to adjust the degree of fluctuation of the sound image localization position by the signal of R by six degrees each to the right and left.
By the similar adjustment, with respect to the other signals, it is possible to adjust the degree of fluctuation to six degrees each to the right and left, which is the same as the degree of fluctuation of the sound image localization position by the signals of C.
Note that, with respect to the signal of L, the signal of LS, and the signal of LB, it is needless to say that the degrees of fluctuation can be adjusted by the procedures similar to those for the signal of R, the signal of RS, and the signal of RB, which are positioned symmetrically with respect to a line connecting a listener and the sound image localization position by the signal of C.
In such a manner, by fluctuating the sound image localization positions for all the audio signals with the same degree of fluctuation, the audio signal processing device 10 according to an embodiment of the present disclosure can perform convolution signal processing, and can improve the sound quality of virtual surround sound after mixing the audio signals to be output to the 2-channel stereo headphones. Furthermore, by fluctuating the sound image localization positions for all the audio signals with the same degree of fluctuation and with the same timing, the audio signal processing device 10 according to an embodiment of the present disclosure can perform convolution signal processing, and can improve the sound quality or expand the sound field of virtual surround sound after mixing the audio signals to be output to the 2-channel stereo headphones.
As described above, with the audio signal processing device 10 according to an embodiment of the present disclosure, by convolving the head-related transfer function, at the time of hearing the virtual surround sound with the 2-channel stereo headphones, a desired sense of virtual sound image localization can be obtained. Then, the audio signal processing device 10 according to an embodiment of the present disclosure performs, prior to convolving the head-related transfer function, signal processing of causing the sound image localization position by each audio signal to fluctuate.
By performing the signal processing for causing the sound image localization position by each audio signal to fluctuate, the audio signal processing device 10 according to an embodiment of the present disclosure can improve the sound quality or expand the sound field of virtual surround sound after mixing the audio signals to be output to the 2-channel stereo headphones, prior to convolving the head-related transfer function. Then, since the audio signal processing device 10 according to an embodiment of the present disclosure causes the sound image localization position to fluctuate by the signal processing, it can improve the sound quality or expand the sound field of virtual surround sound, dispensing with a sensor for detecting a shake of the head of a listener. Therefore, even in the case of outputting sound with existing headphones, by using the audio signal processing device 10 of an embodiment of the present disclosure, it is possible to improve the sound quality or expand the sound field of virtual surround sound.
Note that the above-described embodiment of the present disclosure can convolve a head-related transfer function in conformity with a desired and optional hearing environment or room environment, and uses the head-related transfer function with which a desired sense of virtual sound image localization can be obtained, the head-related transfer function configured to eliminate the properties of measurement microphones or measurement speakers. But the present disclosure is not limited to the case of using such a special head-related transfer function, and is applicable even in the case of convolving a general head-related transfer function.
Steps in a process performed by the device in the present specification do not necessarily have to be performed chronologically in the order illustrated as the sequence diagram or flow chart. For example, steps in the process performed by the device may be performed in an order different from the order illustrated as the flow chart or performed in parallel.
In addition, it is possible to make a computer program for causing hardware such as CPU, ROM, and RAM incorporated in the device, to execute the same function as that of the configuration of the above-described device. In addition, it is possible to provide a storage medium in which the computer program is stored. In addition, it is also possible to implement a series of processes using pieces of hardware by configuring each of the functional blocks illustrated by the functional block diagram using the pieces of hardware.
The preferred embodiment of the present disclosure has been described above with reference to the accompanying drawings, but the present disclosure is not limited to the above examples. It is obvious that a person having ordinary skill in the art to which the present disclosure belongs may conceive various alterations or modifications within the scope of the appended claims, and it should be understood that they will naturally come under the technical scope of the present disclosure.
Additionally, the present technology may also be configured as below.
An audio signal processing device including
a signal processing section that changes, at a time of generating and outputting 2-channel audio signals to be subjected to sound reproduction by two electroacoustic transducing means located at positions in the vicinities of both ears of a listener, from audio signals of a plurality of and more than two channels, virtual sound image localization positions on a circle around the listener, across the virtual sound image localization positions, the virtual sound image localization position that is supposed for each of the plurality of channels of audio signals provided on the circle.
The audio signal processing device according to (1), wherein
the signal processing section changes the virtual sound image localization positions on the circle in synchronization with all the plurality of channels.
The audio signal processing device according to (2), wherein
the signal processing section changes the virtual sound image localization positions on the circle on a predetermined cycle.
The audio signal processing device according to (3), wherein
the signal processing section changes the virtual sound image localization positions on the circle on a cycle close to a block size used in compressing audio data.
The audio signal processing device according to (3), wherein
the signal processing section changes the virtual sound image localization positions on the circle on a random cycle.
The audio signal processing device according to (5), wherein
the signal processing section changes the virtual sound image localization position on a cycle obtained by adding multiplexed random noises having different cycles.
The audio signal processing device according to (6), wherein
the signal processing section changes the virtual sound image localization positions on a cycle obtained by adding multiplexed random noises having different cycles so as to be closer to a normal distribution.
The audio signal processing device according to (6), wherein
the signal processing section changes the virtual sound image localization positions on a cycle obtained by adding two random noises having different cycles.
The audio signal processing device according to any one of (1) to (8), wherein
the signal processing section changes the virtual sound image localization positions, prior to convolving a head-related transfer function with which a sound image is heard to be localized on the virtual sound image localization position with the audio signal of each of the plurality of channels.
An audio signal processing method, including
a step of changing, at a time of generating and outputting 2-channel audio signals to be subjected to sound reproduction by two electroacoustic transducing means located at positions in the vicinities of both ears of a listener, from audio signals of a plurality of and more than two channels, virtual sound image localization positions on a circle around the listener, across the virtual sound image localization positions, the virtual sound image localization position that is supposed for each of the plurality of channels of audio signals provided on the circle.
A computer program that causes a computer to execute
a step of changing, at a time of generating and outputting 2-channel audio signals to be subjected to sound reproduction by two electroacoustic transducing means located at positions in the vicinities of both ears of a listener, from audio signals of a plurality of and more than two channels, virtual sound image localization positions on a circle around the listener, across the virtual sound image localization positions, the virtual sound image localization position that is supposed for each of the plurality of channels of audio signals provided on the circle.
10 audio signal processing device
100 signal processing section
Number | Date | Country | Kind |
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2012-128989 | Jun 2012 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2013/062849 | 5/7/2013 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2013/183392 | 12/12/2013 | WO | A |
Number | Name | Date | Kind |
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20090214045 | Fukui | Aug 2009 | A1 |
20100246831 | Mahabub | Sep 2010 | A1 |
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3-214897 | Mar 1991 | JP |
2007-214815 | Aug 2007 | JP |
2009-212944 | Sep 2009 | JP |
2009-212944 | Sep 2009 | JP |
2011-9842 | Jan 2011 | JP |
2012-506673 | Mar 2012 | JP |
WO 9513690 | May 1995 | WO |
Entry |
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International Search Report issued Jun. 11, 2013 in PCT/JP2013/062849. |
Number | Date | Country | |
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20150117648 A1 | Apr 2015 | US |