Description
Title of Invention
AUDIO SIGNAL PROCESSING DEVICE, AUDIO SIGNAL PROCESSING
METHOD, AND 5 COMPUTER PROGRAM
Technical Field
[0001]
The present disclosure relates to an audio signal processing device, an audio
10 signal processing method, and a computer program.
Background Art
[0002]
There is a case where, when a listener wears headphones on the head of the
15 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.
20 [0003]
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
25 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).
[0004]
In the case of multi-channels including three or more channels, as with a
30 case of two channels, speakers are disposed at virtual sound image localization
positions of the respective channels, and head-related transfer functions for the
3
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.
5 [0005]
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
10 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).
15 Citation List
Patent Literature
[0006]
Patent Literature 1: WO 95/013690
Patent Literature 2: JP 03-214897A
20 Patent Literature 3: JP 2011-009842A
Summary of Invention
Technical Problem
[0007]
25 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,
30 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
4
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.
5 [0008]
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.
10 [0009]
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
15 hearing with speakers actually disposed.
Solution to Problem
[0010]
According to the present disclosure, there is provided an audio signal
20 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
25 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.
[0011]
According to the present disclosure, there is provided an audio signal
30 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
5
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 5 provided on the
circle.
[0012]
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
10 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
15 is supposed for each of the plurality of channels of audio signals provided on the
circle.
Advantageous Effects of Invention
[0013]
20 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
25 actually disposed.
Brief Description of Drawings
[0014]
[FIG. 1] FIG. 1 is an explanatory diagram illustrating an example of speaker
30 arrangement for 7.1-channel multichannel surround sound compliant with the
international telecommunications union radiocommunication sector (ITU-R).
6
[FIG. 2] FIG. 2 is an explanatory diagram illustrating a configuration example of an
audio signal processing device 10 according to an embodiment of the present
disclosure.
[FIG. 3] FIG. 3 is an explanatory diagram illustrating a configuration example of the
audio signal processing device 10 according to an embodiment 5 of the present
disclosure.
[FIG. 4A] FIG. 4A is an explanatory diagram illustrating a configuration example of
a signal processing section 100.
[FIG. 4B] FIG. 4B is an explanatory diagram illustrating a configuration example of
10 the signal processing section 100.
[FIG. 4C] FIG. 4C is an explanatory diagram illustrating a configuration example of
the signal processing section 100.
[FIG. 4D] FIG. 4D is an explanatory diagram illustrating a configuration example of
the signal processing section 100.
15 [FIG. 4E] FIG. 4E is an explanatory diagram illustrating a configuration example of
the signal processing section 100.
[FIG. 4F] FIG. 4F is an explanatory diagram illustrating a configuration example of
the signal processing section 100.
[FIG. 4G] FIG. 4G is an explanatory diagram illustrating a configuration example of
20 the signal processing section 100.
[FIG. 5] FIG. 5 is a flow chart illustrating an operation example of an audio signal
processing device 10 according to an embodiment of the present disclosure.
[FIG. 6A] FIG. 6A is an explanatory diagram illustrating an example of variations in
parameter at the time of causing an audio signal to fluctuate.
25 [FIG. 6B] FIG. 6B is an explanatory diagram illustrating an example of variations in
parameters at the time of causing an audio signal to fluctuate.
[FIG. 7] FIG. 7 is an explanatory diagram illustrating the width of fluctuation of the
signal of C.
[FIG. 8] FIG. 8 is an explanatory diagram illustrating the width of fluctuation of the
30 signal of R.
[FIG. 9] FIG. 9 is an explanatory diagram illustrating the width of fluctuation of the
7
signal of R.
[FIG. 10] FIG. 10 is an explanatory diagram illustrating the width of fluctuation of
the signal of R.
[FIG. 11] FIG. 11 is an explanatory diagram illustrating the width of fluctuation of
5 the signal of RS.
[FIG. 12] FIG. 12 is an explanatory diagram illustrating the width of fluctuation of
the signal of RB.
Description of Embodiments
10 [0015]
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
15 explanations will be omitted.
[0016]
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
20 Sound]
[Configuration Example of Audio Signal Processing Device]
[Operation Example of Audio Signal Processing Device]
<2. Conclusion>
[0017]
25 1. Embodiment of the Present Disclosure
[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. FIG. 1 is an explanatory diagram
illustrating the example of speaker arrangement for 7.1 channel multichannel
30 surround sound compliant with the international telecommunications union
radiocommunication sector (ITU-R), which is an example of multichannel surround
8
sound. The example of speaker arrangement of the 7.1 channel multichannel
surround sound will be described below with reference to FIG. 1.
[0018]
The example of speaker arrangement of the 7.1 channel multichannel
surround sound compliant with ITU-R is defined, as illustrated in 5 FIG. 1, such that
speakers of respective channels are positioned on a circle around a listener position
Pn.
[0019]
In FIG. 1, a front position C of the listener Pn is the speaker position of a
10 center channel. Positions LF and RF, which are positioned on opposite sides across
the speaker position C of the center channel and are away from each other by an
angle range of 60 degrees, represent the speaker positions of a left front channel and
a right front channel, respectively.
[0020]
15 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
20 channel, and the speaker positions LB and RB are the speaker positions of a left rear
channel and a right rear channel.
[0021]
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
25 left ears of the listener Pn, are used as over ear headphones.
[0022]
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
30 speaker positions C, LF, RF, LS, RS, LB, and RB in FIG. 1 to be virtual sound image
localization directions. Thus, in such manner as will be described hereafter, a
9
selected head-related transfer function is convolved with the audio signal of each
channel of the multichannel surround sound audio signals in 7.1 channels.
[0023]
Note that the following description will be made on the basis of the 7.1-
channel multichannel surround sound illustrated in FIG. 1, 5 but the multichannel
surround sound of the present disclosure is not limited to such an example. For
example, 5.1 channel multichannel surround sound has a speaker arrangement in
which speakers positioned at the speaker positions LB and RB are removed from the
speaker arrangement of the 7.1-channel multichannel surround sound illustrated in
10 FIG. 1.
[0024]
The example of speaker arrangement in 7.1-channel multichannel surround
sound is described above with reference to FIG. 1. Next, a configuration example
of an audio signal processing device according to an embodiment of the present
15 disclosure will be described.
[0025]
[Configuration Example of Audio Signal Processing Device]
FIG. 2 and FIG. 3 are explanatory diagrams illustrating a configuration
example of an audio signal processing device 10 according to an embodiment of the
20 present disclosure. The configuration example of the audio signal processing
device 10 according to an embodiment of the present disclosure will be described
below with reference FIG. 2 and FIG. 3.
[0026]
The example illustrated in these FIG. 2 and FIG. 3 is an example of the case
25 where electroacoustic transducing means for converting electric signals to bring
sound to the ear of the listener Pn is 2-channel stereo over ear headphones including
a headphone driver 120L for a left channel and a headphone driver 120R for a right
channel.
[0027]
30 Note that, in these FIG. 2 and FIG. 3, the audio signals of the channels to be
provided to the speaker positions C, LF, RF, LS, RS, LB, and RB in FIG. 1 are
10
denoted by the same reference characters C, LF, RF, LS, RS, LB, and RB. Here, in
FIG. 2 and FIG. 3, an LFE channel refers to a low frequency effect channel and this
is sound having no sound image localization direction that can be normally
determined, and thus, in this example, this is considered to be an audio channel that
is not to be convolved with a head-related 5 transfer function.
[0028]
As illustrated in FIG. 2, the 7.1-channel audio signals LF, LS, RF, RS, LB,
RB, C, and LFE are provided to level adjusting sections 71LF, 71LS, 71RF, 71RS,
71LB, 71RB, 71C, and 71LFE, respectively, and the audio signals are subject to level
10 adjustment.
[0029]
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
15 provided to A/D converters 73LF, 73LS, 73RF, 73RS, 73LB, 73RB, 73C, and 73LFE,
respectively, to be converted into digital audio signals.
[0030]
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
20 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.
[0031]
In each of the head-related transfer function convolution processing sections
25 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.
[0032]
30 In addition, in this example, each of the head-related transfer function
convolution processing sections 74LF, 74LS, 74RF, 74RS, 74LB, 74RB, 74C, and
11
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.
[0033]
Furthermore, in this example, it is assumed that the 5 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.
10 [0034]
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
15 section) and an adding section 75R for the right channel (hereafter, referred to as R
adding section) of the 2-channel stereo headphones.
[0035]
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
20 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.
[0036]
Then, the L adding section 75L provides the result of the addition to, as
25 illustrated in FIG. 3, a D/A converter 111L through a level adjusting section 110L, as
a synthesized audio signal SL for a headphone driver 120L for the left channel.
[0037]
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
30 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
12
frequency effect channel component LFE.
[0038]
Then, the R adding section 75R provides the result of the addition to, as
illustrated in FIG. 3, a D/A converting section 111R through a level adjusting section
110R, as a synthesized audio signal SR for a headphone driver 5 120R for the right
channel.
[0039]
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
10 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.
[0040]
15 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.
[0041]
20 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.
[0042]
Then, the audio signals from the current-voltage converting sections 112L
25 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.
[0043]
Then, output audio signals from the gain adjusting sections 114L and 114R
30 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
13
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.
[0044]
In the audio signal processing device 10, according 5 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.
[0045]
10 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 FIG. 1 is merely simulated, it is difficult to reproduce sound
quality and a sound field at the time of hearing with the speakers actually disposed as
15 illustrated in FIG. 1. This is because, as described above, 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 the listener is not necessarily fixed but moves
slightly. Therefore, at the time of hearing the sound from speakers, the distances
20 from the speakers to the ears of the listener and the angles (directions) to the speakers
viewed from the listener are not constant, and thus, when the environment of the
speakers is simply simulated, it is difficult to reproduce the sound quality and the
sound field at the time of hearing with speakers similarly disposed.
[0046]
25 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 FIG. 2, sound quality and a sound field at the time of
hearing with speakers actually disposed are reproduced at the time of reproducing the
audio signals in the multichannel surround sound system, with 2-channel audio
30 signals. Specifically, the signal processing section 100 mixes each of the 7.1-
channel audio signals LF, LS, RF, RS, LB, RB, and C with slight audio signals of
14
other channels and performs a process of causing a sound image to slightly fluctuate.
[0047]
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 5 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.
[0048]
10 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 FIG. 2 and FIG. 3. Next, a configuration example of the
signal processing section 100 included in the audio signal processing device 10
according to an embodiment of the present disclosure will be described.
15 [0049]
[Configuration Example of Signal Processing Section]
FIG. 4A to FIG. 4G are explanatory diagrams illustrating a configuration
example of the signal processing section 100 included in the audio signal processing
device 10 according to an embodiment of the present disclosure. The configuration
20 example of the signal processing section 100 included in the audio signal processing
device 10 according to an embodiment of the present disclosure will be described
below with reference to FIG. 4A to FIG. 4G.
[0050]
FIG. 4A to FIG. 4G illustrates the configuration example of the signal
25 processing section 100 for performing signal processing on each of the 7.1-channel
audio signals LF, LS, RF, RS, LB, RB, and C. For example, FIG. 4A illustrates a
configuration for performing the above signal processing on L out of the 7.1-channel
audio signals.
[0051]
30 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
15
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.
[0052]
For example, at the time of performing the above-described 5 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
10 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.
15 [0053]
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
20 100 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
25 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.
30 [0054]
In addition, for example, at the time of performing the above-described
16
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 5 the signal of RB and
the signal of LB 60 degrees clockwise away from the signal of RB.
[0055]
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
10 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.
[0056]
15 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
20 speakers in the multichannel surround sound system actually disposed.
[0057]
FIG. 4A illustrates amplifiers 131a, 131b, and 131c and adders 131d and
131e. The amplifiers 131a, 131b, and 131c each amplify the signal of L out of the
7.1-channel audio signals by a predetermined amount, and output the resultant signal.
25 [0058]
The amplifier 131a amplifies the signal of L by f (1-2f). As the values
of f and f, those which will be described hereafter are used. In addition, the
amplifier 131b amplifies the signal of L by F_PanS*f(f*). Similarly, the
amplifier 131c amplifies the signal of L by F_PanF*f(f*(1-)). Note that 
30 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
17
hereafter are used. Note that f, f, , 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.
[0059]
The adder 131d adds the signal of LS to the signal of 5 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
10 head-related transfer function.
[0060]
FIG. 4B illustrates amplifiers 132a, 132b, and 132c and adders 132d and
132e. The amplifiers 132a, 132b, and 132c each amplify the signal of C out of the
7.1-channel audio signals by a predetermined amount, and output the resultant signal.
15 [0061]
The amplifier 132a amplifies the signal of C by c(1-2c). As the values
of c and c, those which will be described hereafter are used. In addition, the
amplifier 132b amplifies the signal of C by c(c*). Similarly, the amplifier 132c
amplifies the signal of C by c(c*(1-)).
20 [0062]
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
25 processing section 100 are signals to be subjected to the processing of convolving the
head-related transfer function.
[0063]
FIG. 4C illustrates amplifiers 133a, 133b, and 133c and adders 133d and
133e. The amplifiers 133a, 133b, and 133c each amplify the signal of R out of the
30 7.1-channel audio signals by a predetermined amount, and output the resultant signal.
[0064]
18
The amplifier 133a amplifies the signal of R by f(1-2f). As the values
of f and f, those which will be described hereafter are used. In addition, the
amplifier 133b amplifies the signal of R by F_PanF*f(f*). Similarly, the
amplifier 133c amplifies the signal of R by F_PanS*f(f*(1-)).
5 [0065]
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
10 processing section 100 are signals to be subjected to the processing of convolving the
head-related transfer function.
[0066]
FIG. 4D illustrates amplifier 134a, 134b, and 134c and adders 134d and
134e. The amplifiers 134a, 134b, and 134c each amplify the signal of LS out of the
15 7.1-channel audio signals by a predetermined amount, and output the resultant signal.
[0067]
The amplifier 134a amplifies the signal of LS by s(1-2s). As the
values of s and s, those which will be described hereafter are used. In addition,
the amplifier 134b amplifies the signal of LS by S_PanS*s(s*). Similarly, the
20 amplifier 134c amplifies the signal of LS by S_PanF*s(s*(1-)).
[0068]
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
25 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 headrelated
transfer function.
[0069]
FIG. 4E illustrates amplifiers 135a, 135b, and 135c and adders 135d and
30 135e. The amplifier 135a, 135b, and 135c each amplify the signal of RS out of the
7.1-channel audio signals by a predetermined amount, and output the resultant signal.
19
[0070]
The amplifier 135a amplifies the signal of RS by s(1-2s). As the
values of s and s, those which will be described hereafter are used. In addition,
the amplifier 135b amplifies the signal of RS by S_PanF*s(s*). Similarly, the
amplifier 135c amplifies the signal of RS by S_5 PanS*s(s*(1-)).
[0071]
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
10 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.
[0072]
FIG. 4F illustrates amplifier 136a, 136b, and 136c and adders 136d and
15 136e. The amplifiers 136a, 136b, and 136c each amplify the signal of LB out of the
7.1-channel audio signals by a predetermined amount, and output the resultant signal.
[0073]
The amplifier 136a amplifies the signal of LB by b(1-2b). As the
values b and b, those which will be described hereafter are used. In addition, the
20 amplifier 136b amplifies the signal of LB by B_PanS*b(b*). Similarly, the
amplifier 136c amplifies the signal of LB by B_PanB*b(b*(1-)).
[0074]
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
25 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.
[0075]
30 FIG. 4G illustrates amplifiers 137a, 137b, and 137c and adder 137d and
137e. The amplifiers 137a, 137b, and 137c each amplify the signal of RB out of the
20
7.1-channel audio signals by a predetermined amount, and output the resultant signal.
[0076]
The amplifier 137a amplifies the signal of RB by b(1-2b). As the
values of b and b, those which will be described hereafter are used. In addition,
the amplifier 137b amplifies the signal of RB by B_PanB*b(5 b*). Similarly, the
amplifier 137c amplifies the signal of RB by B_PanS*b (b*(1-)).
[0077]
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
10 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.
[0078]
15 As the above-described c, c, f, f, s, s, b, and b, the following
values are used.
[0079]
c is approximately equal to 1.0
c is approximately equal to 0.1
20 f is approximately equal to 1.0
f is approximately equal to 0.1
s is approximately equal to 1.0
s is approximately equal to 0.1*(60.0/210.0)
b is approximately equal to 1.0
25 b is approximately equal to 0.1*(60.0/90.0)
[0080]
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,
30 correction is made in conformity with the angles of speakers to which the channel is
distributed.
21
[0081]
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 5 cannot be distributed
with the same angle will be described hereafter.
[0082]
F_Pan is approximately equal to 0.05
F_PanF=(1.0+F_Pan)
10 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))
15 B_PanS=(1.0+B_Pan)
B_PanB=(1.0-B_Pan)
[0083]
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
20 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.
[0084]
25 The respective audio signals distributed in such a manner are distributed
cyclically with  ranging between 0 and 1 so as to have the same rotation in
accordance with  according to the same speaker arrangement. The cycle of this 
includes, for example, a fixed pattern and a pattern to randomly distribute. These
patterns will be described hereafter.
30 [0085]
As described above, the configuration example of the signal processing
22
section 100 included in the audio signal processing device 10 according to an
embodiment of the present disclosure has been described with reference to FIG. 4A
to FIG. 4G. Next, the operation of the audio signal processing device 10 according
to an embodiment of the present disclosure will be described.
5 [0086]
[Operation Example of Audio Signal Processing Device]
FIG. 5 is a flow chart illustrating an operation example of the audio signal
processing device 10 according to an embodiment of the present disclosure. The
flow chart illustrated in FIG. 5 represents an operation example of the audio signal
10 processing device 10 at the time of performing an operation to control the
localization positions of sound images with respect to audio signals in the
multichannel surround sound system. The operation example of the audio signal
processing device 10 according to an embodiment of the present disclosure will be
described below with reference to FIG. 5.
15 [0087]
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
20 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
25 of another channel (step S103).
[0088]
At the time of causing the parameter  to vary cyclically, the signal
processing section 100 may cause the parameter  to vary on a cycle close to a block
size used in compressing audio data, which is hard for human ears to perceive. In
30 addition, the signal processing section 100 may cause the parameter  to vary on a
random cycle. In addition, the signal processing section 100 may perform a control
23
in such a manner as to cause the audio signal of each channel to fluctuate using the
sum of multiplexed parameters  that are caused to vary on different cycles.
[0089]
Here, the parameter  used at the time of causing an audio signal to fluctuate
will be described. FIG. 6A and FIG. 6B are explanatory 5 diagrams illustrating
examples of variations in parameter  at the time of causing an audio signal to
fluctuate. What is illustrated in FIG. 6A is the example of variations at the time of
causing the parameter  to vary cyclically illustrated in the form of a graph. In FIG.
6A, the parameter  is caused to be in proportional to time on a cycle of 40 ms. In
10 addition, what is illustrated in FIG. 6B is the example of variation at the time of
causing the parameter  to vary on a random cycle illustrated in the form of a graph.
[0090]
With respect to the pattern in which the parameter  is caused to randomly
vary as illustrated in FIG. 6B, adding multiplexed random noises that range between
15 -1 and +1 and have different cycles has a greater effect of improvement than making
variations with a simple white noise (or M sequence). In addition, a larger number
of random noises to be added (the added random noise closer to have a normal
distribution) tends to have a greater effect of improvement. In other words, when a
white noise (or M sequences) ranging between -1 and 1, which have no (little)
20 correlation, is denoted by WN(n),
n=1: =WN(0)+1.0 (Random Noise)
n=2: =(WN(0)+WN(1))/2.0+1.0 (Triangular Distribution)
:
n=8: =(WN(0)+...+WN(7))/8.0+1.0 (Pseudo Normal Distribution)
25 it is thus confirmed that the sound quality and the sound field tend to be further
improved as n becomes greater.
[0091]
Subsequently, an example of the width of fluctuation and angle correction of
the audio signal of each channel are illustrated. FIG. 7 is an explanatory diagram
30 illustrating the width of fluctuation of the signal of C. The signal of C is split and
distributed to a signal of L and a signal of R that are positioned at the right and left
24
side and at regular intervals. The amounts of distribution are, for example, 80% for
C and a width of between 0 and 20% for L and R. Thereby, the sound image
localization position by the signal of C is to fluctuate clockwise and
counterclockwise within a range of six degrees across the original sound image
localization position by the signal of C. In other words, the 5 above-described
parameters  c and c have the relationship in which one is ten times as much as
another so as to cause the sound image localization position by the signal of C to
fluctuate clockwise and counterclockwise within a range of six degrees, which is
1/10 of an interval of 60 degrees between L and R.
10 [0092]
FIG. 8 is an explanatory diagram illustrating the width of fluctuation of the
signal of R. The signal of R is split and distributed to a signal of L and a signal of
RS that are positioned at the right and left but not at regular intervals. Therefore, to
distribute the signal of R, the position of R is first temporality set at a position at
15 which L and RS are positioned at regular intervals. In FIG. 8, the provisionally set
position of R is denoted by R'. The position of R' is at a position deviating
clockwise by 15 degrees from the position of R.
[0093]
In addition, when the amounts of distribution are, as with the signal of C,
20 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
25 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.
[0094]
FIG. 9 is an explanatory diagram illustrating the width of fluctuation of the
30 signal of R. FIG. 9 illustrates how to adjust the degree of fluctuation of the sound
image localization position by the signal of R from 15 degrees to 6 degrees. The
25
distribution of 80% for R and a width of between 0 and 20% for L and RS is changed
into distribution of 92% for R and a width of between 0 and 8% for L and RS such
that the degree of fluctuation becomes six degrees. This is a value obtained by
multiplexing 20% distributed for L and RS by 60/150. In addition, as with the
signal of C, by making the degree of fluctuation six degrees, the 5 position of R' and
the positions of L and RS to which the signal of R is distributed are changed into the
positions of R', L' and RS' as illustrated on the right side of FIG. 9.
[0095]
With this, the degree of fluctuation is adjusted into the width the same as
10 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.
[0096]
FIG. 10 is an explanatory diagram illustrating the width of fluctuation of the
15 signal of R. FIG. 10 illustrates how to align the sound image localization position
of the signal of R with the original position. By shifting the sound image
localization position that deviates clockwise by six degrees, counterclockwise by six
degrees, the sound image localization position of the signal of is aligned with the
original position. In addition, the positions of L' and RS' are similarly shifted
20 counterclockwise by six degrees. Thereby, the positions of R', L' and RS' are
changed to the positions of R'', L'' and RS''. Note that the position of R'' is the same
as the position of R.
[0097]
To shift the position of L' counterclockwise by six degrees, as illustrated in
25 FIG. 10, a value obtained by multiplying the degree of fluctuation of 8% by 6/30 is
added. In contrast, to shift the position of RS' counterclockwise by six degrees, as
illustrated in FIG. 10, the value obtained by multiplying the degree of fluctuation of
8% by 6/30 is subtracted. The amounts of distribution are thereby changed to a
width of between 0 and 9.6% for L and a width of between 0 and 6.4% for RS,
30 although the amount of distribution for R remains at 92%.
[0098]
26
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 5 original position of
R. These parameters for adjusting the degrees of fluctuation are f, f, F_PanF,
and F_PanS out of the above-described parameters. By setting f, f, 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
10 each to the right and left.
[0099]
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
15 signals of C.
[0100]
FIG. 11 is an explanatory diagram illustrating the width of fluctuation of the
signal of RS. The signal of RS is also split and distributed to a signal of R and a
signal of LS that are positioned at the right and left but not at regular intervals.
20 Therefore, by a procedure similar to the above-described procedure for the signal of
R, the degree of fluctuation of the sound image localization position by the signal of
RS is adjusted to six degrees each to the right and left. In other words, the sound
image localization position by the signal of RS is provisionally set such that R and
LS are positioned at regular intervals, the amounts of distribution are adjusted such
25 that the degree of fluctuation is made six degrees across the provisional sound image
localization position, and the degree of fluctuation of the sound image localization
position by the signal of RS is adjusted to six degrees each to the right and left by the
method of returning the provisional sound image localization position to the original
sound image localization position. These parameters for adjusting the degree of
30 fluctuation of the sound image localization position by the signal of RS are s, s,
S_PanF, and S_PanS out of the above-described parameters. By setting s, s,
27
S_PanF, and S_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 RS by six
degrees each to the right and left.
[0101]
FIG. 12 is an explanatory diagram illustrating the width of 5 fluctuation of the
signal of RB. The signal of RB is also split and distributed to a signal of RS and a
signal of LB that are positioned at the right and left but not at regular intervals.
Therefore, by a procedure similar to the above-described procedure for the signal of
R, the degree of fluctuation of the sound image localization position by the signal of
10 RB is adjusted to six degrees each to the right and left. In other words, the sound
image localization position by the signal of RB is provisionally set such that RS and
LB are positioned at regular intervals, the amounts of distribution are adjusted such
that the degree of fluctuation is made six degrees across the provisional sound image
localization position, and the degree of fluctuation of the sound image localization
15 position by the signal of RB is adjusted to six degrees each to the right and left by the
method of returning the provisional sound image localization position to the original
sound image localization position. These parameters for adjusting the degree of
fluctuation of the sound image localization position by the signal of RB are b, b,
B_PanB, and B_PanS out of the above-described parameters. By setting b, b,
20 B_PanB, and B_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 RB to
six degrees each to the right and left.
[0102]
Note that, with respect to the signal of L, the signal of LS, and the signal of
25 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.
[0103]
30 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
28
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 5 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.
10 [0104]
2. Conclusion
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
15 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.
20 [0105]
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
25 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
30 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
29
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.
[0106]
Note that the above-described embodiment of the present disclosure can
convolve a head-related transfer function in conformity with 5 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
10 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.
[0107]
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
15 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.
[0108]
In addition, it is possible to make a computer program for causing hardware
20 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
25 block diagram using the pieces of hardware.
[0109]
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
30 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
30
that they will naturally come under the technical scope of the present disclosure.
[0110]
Additionally, the present technology may also be configured as below.
(1)
An audio signal processing 5 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
10 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.
(2)
15 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.
(3)
The audio signal processing device according to (2), wherein
20 the signal processing section changes the virtual sound image localization
positions on the circle on a predetermined cycle.
(4)
The audio signal processing device according to (3), wherein
the signal processing section changes the virtual sound image localization
25 positions on the circle on a cycle close to a block size used in compressing audio data.
(5)
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.
30 (6)
The audio signal processing device according to (5), wherein
31
the signal processing section changes the virtual sound image localization
position on a cycle obtained by adding multiplexed random noises having different
cycles.
(7)
The audio signal processing device according 5 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.
(8)
10 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.
(9)
The audio signal processing device according to any one of (1) to (8),
15 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.
20 (10)
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
25 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.
(11)
30 A computer program that causes a computer to execute
a step of changing, at a time of generating and outputting 2-channel audio
32
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 5 for each of
the plurality of channels of audio signals provided on the circle.
Reference Signs List
[0111]
10 10 audio signal processing device
100 signal processing section
33
CLAIMS
Claim 1
An audio signal processing device comprising
a signal processing section that changes, at a time of generating and
outputting 2-channel audio signals to be subjected to sound 5 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
10 is supposed for each of the plurality of channels of audio signals provided on the
circle.
Claim 2
The audio signal processing device according to Claim 1, wherein
15 the signal processing section changes the virtual sound image localization
positions on the circle in synchronization with all the plurality of channels.
Claim 3
The audio signal processing device according to Claim 2, wherein
20 the signal processing section changes the virtual sound image localization
positions on the circle on a predetermined cycle.
Claim 4
The audio signal processing device according to Claim 3, wherein
25 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.
Claim 5
The audio signal processing device according to Claim 3, wherein
30 the signal processing section changes the virtual sound image localization
positions on the circle on a random cycle.
34
Claim 6
The audio signal processing device according to Claim 5, wherein
the signal processing section changes the virtual sound image localization
position on a cycle obtained by adding multiplexed random noises 5 having different
cycles.
Claim 7
The audio signal processing device according to Claim 6, wherein
10 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.
Claim 8
15 The audio signal processing device according to Claim 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.
Claim 9
20 The audio signal processing device according to Claim 1, 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.
25
Claim 10
An audio signal processing method, comprising
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
30 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
35
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.
5 Claim 11
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
10 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.