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JPH06165296

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DESCRIPTION JPH06165296
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound field signal reproducing apparatus for performing realistic sound reproduction in an AV
(audio visual) apparatus.
[0002]
2. Description of the Related Art In recent years, in the field of video and audio, sound
reproduction with a large screen and a sense of reality is desired in order to enjoy movies at
home due to the spread of VTRs, and development of hardware corresponding thereto is desired.
There is.
[0003]
In particular, in the sound of movie software of VTR, a Dolby Surround method in which a
speaker is placed side by side or in the rear (or a combination thereof) and played back is
popularized as is practiced in movie theaters. ing.
[0004]
In addition, the high-definition sound reproduction method currently under development is likely
to adopt the 3-1 method 4 channel stereo reproduction of the front 3 channels and the rear 1
channel.
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[0005]
FIG. 6 is a block diagram of a conventional sound field signal reproduction apparatus for
performing realistic sound reproduction.
[0006]
In FIG. 6, the signal ML (t) 2 to be reproduced from the Lch viewed from the listener 8 (t
represents a continuous time, indicating that the signal is a time function, and so on). Is
connected, and the speaker 6 is connected to the signal MR (t) 3 to be reproduced from the Rch
as viewed from the listener 8.
The two signals are further added by an adder 7 which adds them at a certain ratio, and are
added to a speaker 5 disposed at the front center of the listener 8.
[0007]
Also, by processing the two signals ML (t) 2 and MR (t) 3 by processing those two signals, a
surround signal to be reproduced from the rear (the input signal is a speaker in a normal room)
Surround signal S (t), which is input to the surround creating circuit 1 for creating a signal S (t) of
reverberant sound or reflected sound called reverberation sound or reflected sound generated
when emitted from (Signals ML (t) 2 and MR (t) 3 input to the two speakers 9 and 10 disposed at
the left and right rear of the point point to what is usually called a stereo signal.
The above-mentioned surround signals S (t) are also referred to as main signals).
[0008]
The operation of the sound field signal reproduction apparatus configured as described above
will be described with reference to the drawings.
First, in the configuration of FIG. 6, 2ch signals ML (t) 2 and MR (t) 3 reproduced from a VTR etc.
are input to the surround signal generation circuit 1 and calculations such as subtraction and
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addition are performed on those signals. Thus, a surround signal S (t) such as reverberation or
reflected sound is created.
The main signals ML (t) 2 and MR (t) 3 are reproduced from the speakers 4 and 6, respectively,
and the surround signal S (t) is reproduced from the speakers 9 and 10. Also, the main signals
ML (t) 2 and MR (t) 3 are added at a certain ratio by the adder 7, and the added signal is
reproduced from the speaker 5.
[0009]
Also, from a sound signal such as a movie, etc., encoded for Dolby Surround by using a decoder
called Dolby Surround processor etc. instead of the surround signal creation circuit 1 and
encoded in 2ch, The surround signal S (t) reproduced from the rear and the signal reproduced
from the front center which are optimally created on the screen are obtained, and the surround
signal S (t) is obtained from the speakers 9 and 10, the center signal is It may be reproduced
from the speaker 5 as well. The surround signal S (t) should sound, for example, the sound
around the room (sound reflected sound or reverberation sound) projected on the screen, or
behind the viewer when the viewer is on the screen. It is added as a sound.
[0010]
As described above, compared to the 2ch stereo reproduction method using the two speakers in
front usually, the surround sound is added to the sound heard from the front and the sound that
was not heard from the front from the rear, It enables realistic sound reproduction. Further, in
this system, a center speaker is disposed in the front, and the main signals ML (t) 2 and MR (t) 3
are added at an appropriate level and reproduced to thereby localize the front sound image. To
clarify.
[0011]
However, in the above configuration, since the sound to be reproduced is heard as a sound from
the reproduction place of the sound reproduction means, the sound such as the rear etc. for
reproducing the surround signal S (t) There is a problem that a speaker as a regenerating means
is required, and a space for placing the speaker is necessary.
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[0012]
An object of the present invention is to provide a sound field signal reproduction apparatus
capable of making a sound to be reproduced audible as a sound from a place other than the
reproduction place of the sound reproduction means in consideration of the conventional
problems. is there.
[0013]
According to the present invention, there is provided an input means for inputting one sound
signal, a dividing means for dividing the input sound signal into at least two sound signals, and
the divided sound signals. The system comprises at least two adjustment means to be input
respectively, and at least two sound reproduction means connected to each adjustment means to
reproduce the transmitted sound reproduction signal into a sound at a predetermined place, the
adjustment means being a listener The sound field signal reproducing apparatus adjusts the
amplitude and delay time of the divided sound signal so as to be heard as a sound from a place
other than a predetermined place, and outputs the sound signal as a sound reproduction signal.
[0014]
According to the present invention, the input means receives one sound signal, the dividing
means divides the input sound signal into at least two sound signals, and the adjusting means
receives the divided sound signals. The amplitude and the delay time of the sound signals are
adjusted respectively to the listener so that they can be heard as sounds from places other than a
predetermined place, and output as a sound reproduction signal, and the sound reproduction
means determines the sound reproduction signal Play to the sound at the place.
[0015]
Embodiments of the present invention will be described hereinbelow with reference to the
drawings.
[0016]
FIG. 1 is a block diagram of a sound field signal reproduction apparatus according to a first
embodiment of the present invention.
That is, two signals of the signal ML (t) 2 to be reproduced from Lch viewed from the listener 8
and the signal MR (t) 3 to be reproduced from Rch viewed from the listener 8 process these two
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signals By doing this, it is input to the surround signal creation circuit 1 that creates a surround
signal S (t) such as reverberation and reflected sound to be reproduced from the rear.
An A / D converter 21 for converting a surround signal S (t) of an analog signal into a digital
signal is connected to the surround signal generation circuit 1 (the input terminal of the A / D
converter 21 constitutes an input unit), The output of the D converter 21 is divided into two
signals (this branch circuit constitutes a dividing means), and the head transfer function is timed
so that the sound is localized leftward or leftward to the listener 8. It is input to FIR filters 11 and
12 which are adjusting means for performing digital processing in a region and realizing it.
HL (n), hR (n) (n is actually nT in FIR filters 11 and 12 and T is a sampling time, but generally T is
omitted).
Also, n is a natural number.
) Is an impulse response when an impulse is input to the FIR filters 11 and 12.
[0017]
The output signal ShL (n) of the FIR filter 11 is branched into two, one of which is input to the
adder 15 and the other is input to another adder 16 via the delay unit 13 and the output signal
ShR of the FIR filter 12 Similarly to the output signal ShL (n), (n) is branched into two, one being
input to the adder 16 and the other being input to the adder 15 via the delay unit 14. The delay
units 13 and 14, which are delay means, are constituted by a circulating memory or the like
using a DRAM or the like, and delay the input digital signal by a certain time, and τ1 represents
the delay time divided by the sampling period. ing.
[0018]
Connected to the adder 15 is a D / A converter 17 which converts a digital signal into an analog
signal. The D / A converter 18 is connected to the other adder 16. Further, the adders 15, 16 as
addition means add a plurality of input signals at an arbitrary ratio.
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[0019]
Furthermore, the D / A converter 17 is connected to the adder 19, the adder 19 is connected to
the speaker 4, and the signal ML (t) 2 is input to the adder 19. Further, the D / A converter 18 is
connected to the adder 20, the adder 20 is connected to the speaker 6, and the signal MR (t) 3 is
input to the adder 20. The adders 19 and 20 constitute signal addition means, and the speakers
4 and 6 constitute sound reproduction means.
[0020]
Next, a method of localizing the sound to the left rear of the listener 8 using the speakers 4 and 6
placed in front will be described with reference to FIG.
[0021]
In FIG. 2, 1-1 is a transmitter that generates the surround signal S (t) independently, h1 (t) is the
position of the speaker 4 and the left ear of the listener 8 (specifically, an impulse is input to the
speaker 4 The response is at the position of the eardrum at the time, but when performing
measurement, it is called the impulse response (hereinafter referred to as impulse response) in
order to explain in the time domain, at the position of the entrance of the ear canal.
However, similar results can be obtained even in the frequency domain. Moreover, what
converted the impulse response into a frequency characteristic by Fourier-transforming is called
a transfer function. H2 (t) is an impulse response at the position of the right ear of the speaker 4
and the listener 8, h3 (t) is an impulse response at the position of the left ear of the speaker 6
and the listener 8, h4 (t) Is an impulse response at the position of the right ear of the speaker 6
and the listener 8, 27 is a speaker placed behind the listener on the left, h5 (t) is the position of
the speaker 27 and the left ear of the listener 8 The impulse response at h6 (t) is the impulse
response at the positions of the speaker 27 and the right ear of the listener 8. The same
functions as those in FIG. 1 and FIG. 6 are indicated by the same numbers.
[0022]
In such a configuration, when the signal S (t) is emitted from the speaker 27, the sound reaching
the ear of the listener 8 is, in the left ear L (t),
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[0024]
In the right ear R (t),
[0026]
(In fact, the speaker's own impulse response etc. will also be folded, but this shall be ignored.
Also, it may be considered that the impulse response of the speaker or the like is included in h5
(t) and h6 (t)).
[0027]
Also, considering the impulse response and the signal S (t) as discrete digital signals, L (t) → L (n)
R (t) → R (n) h5 (t) → h5 (n) h6 Expressing (t) → h 6 (n) S (t) → S (n), (Equation 1) and (Equation
2) are as follows.
[0030]
Here, N is the length of the impulse responses h5 (n) and h6 (n).
Similarly, when the signal S (t) radiates from the speakers 4 and 6, the sound reaching the
listener 8 is, in the left ear L '(t),
[0032] In the right ear R '(t),
[0034] [0034] Similarly,
[0037] 【0037】となる。 Here, it is assumed that sounds are heard from the same direction
if the head related transfer functions are equal (this assumption is generally correct),
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[0039] 【0039】のとき、
[0042] 【0042】のとき、
[0044] Therefore, in order to make the listener 8 be able to hear from the left rear by using the
speaker 4 and the speaker 6, hL (n) should be satisfied so as to satisfy the equations (10) and
(12). , HR (n) may be determined. For example, if Equations (10) and (12) are rewritten in the
frequency domain representation, the convolution operation will be replaced by multiplication,
and thereafter the respective impulse responses will be FFTed into transfer functions. The
impulse responses of the FIR filters 11 and 12 can be obtained from the two (Equation 10) and
(Equation 12) because the impulse responses of the FIR filters 11 and 12 are obtained by
measurement. Using hL (n) and hR (n) determined in this way, the signal S (n) and hL (n) from the
speaker 4 and the signals S (n) and hR (n) from the speaker 6 By emitting the folded-in, it is
possible to make the listener 8 feel that a sound is being emitted from the rear without actually
sounding the rear speaker 27.
[0045] It is the FIR filters 11 and 12 that actually perform the convolution operation. The basic
configuration of the FIR filters 11 and 12 is shown in FIG. In FIG. 3, delay elements 23 for
delaying the signal by .tau. Time are connected in series to the input terminal 22 for inputting
the signal, and at both ends of these delay elements 23, multiplication of an input signal with a
so-called tap coefficient is performed. A multiplier 24 is connected. The other ends of the
multipliers 24 are connected to an adder 25 that adds a plurality of input signals, and an output
terminal 26 that outputs the added signal is connected to the adder 25. H (n) (n: 0 to N-1) of the
multiplier 24 is an impulse response having a certain characteristic set as a tap coefficient.
Usually, such a FIR filter uses a DSP or a dedicated LSI that performs multiplication and addition
at high speed. As shown in the figure, the impulse response h (n) is set as a tap coefficient to the
multiplier 24, and a delay time corresponding to the sampling frequency when converting an
analog signal to a digital signal is set to the delay element 23 and input. By repeating
multiplication and addition and delays for the signal shown in (3) and (4), respectively. Therefore,
by inputting a signal to this FIR filter, the characteristic of the impulse response h (n) is
convoluted into the input signal and output. The above is the case of a digital signal, so in
practice the A / D converter converts an analog signal to a digital signal before this FIR filter and
the D / A converter converts a digital signal to an analog signal after this FIR filter. It is necessary
(it omits in FIG. 3).
[0046] Next, the operation of this embodiment will be described with reference to FIG. 2ch
signals ML (t) 2 and MR (t) 3 normally reproduced from VTR etc. are input to the surround signal
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creation circuit 1, and reverberation or reflected sound etc. are performed by performing
operations such as subtraction and addition on those two signals. The surround signal S (t) is
generated by the A / D converter 21 and the surround signal S (t) is converted into a digital
signal S (n). This S (n) is divided into two signals, and as described above, the FIR filter having
impulse responses hL (n) and hR (n) as tap coefficients to localize the sound to the left or left of
the listener 8 Input to 11 and 12 and perform convolution operation. These results are each
branched into two, one of which is input as it is to adders 15 and 16, the other of which is
delayed by τ 1 by delay units 13 and 14, and is input to adders 16 and 15, respectively. , Is
added at a certain rate. That is, for delayed ones, the left and right are set opposite to those not
delayed. As a result, the sound is localized leftward (or backward) with respect to the listener 8
by the undelayed signals ShL (n) and ShR (n), and the delayed signal is left-right reversed ShR
(n− Due to τ1) and ShL (n−τ1), the sound is localized to the right (or back) with a delay of
τ1 from the sound on the left (or back) with respect to the listener 8.
[0047] Thus, by giving each signal a time difference (ie, between ShL (n) and ShL (n-τ1), and
between ShR (n) and ShR (n-τ1)), left and right Can separate the signal for localizing the sound
to the side (or the rear) of the side, and the sense of the side or rear localization (here, the sense
of localization means the vague feeling that it is sounding on the side or rear It is possible to
make clear the point, not the localization of a clear sound image as used normally, and so on. For
example, since the surround signal S (t) is usually a monaural signal, if sound is simultaneously
presented without giving a time difference to the left and right signals contrary to the above, the
sound image is localized in the middle. In order to avoid this, these delay units 13 and 14 are
necessary (.tau.1 is preferably about 10 msec).
[0048] Next, the output signals of the adders 15 and 16 are input to the D / A converters 17 and
18, converted from digital signals to analog signals, and the converted signals and the main
signals ML (t) 2 and MR (t 3) are respectively input to the adders 19 and 20, added, and output
from the speakers 4 and 6. Here, by changing the ratio of addition of the main signals ML (t) 2
and MR (t) 3 and the surround signal S (t) processed as described above, adjustment of the
realism and naturalness or preference of the listener Is possible.
[0049] Thus, processing is performed using only two FIR filters 11 and 12 that process sound
localization to the left side (or rear side) with respect to the listener 8 (processing so as to
localize sound to the right side or rear side) Localize the sound to the left and right sides (or the
back) of the listener by adding delays set to the left and right of the outputs from the respective
FIR filters 11 and 12 and adding delays to the outputs from the respective FIR filters 11 and 12)
be able to. In addition, the combination with the main signal enables more realistic sound
reproduction.
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[0050] Further, in the above embodiment, the main signals ML (t) 2 and MR (t) 3 and the sound
reproduction signals of the signals whose amplitudes and delay times have been adjusted are
added by the adders 19 and 20, respectively. Although reproduction is performed from the same
speaker, respectively, the main signals ML (t) 2 and MR (t) 3 may be reproduced by different
speakers.
[0051] Further, although the number of adjustment means is two in the above embodiment, the
present invention is not limited to this. For example, the sound signal may be divided by three or
more and divided by three or more. Of course, the reproduction may be performed by the above
speaker.
[0052] Next, a second embodiment of the present invention will be described with reference to
the drawings. The difference from the first embodiment is the FIR filters 11 and 12 in FIG. The
first difference is that when the signals processed by the FIR filters 11 and 12 are output from
the speakers 4 and 6, the ear on the side closer to the direction in which the listener 8 hears the
sound (ie, the sound to the left) The characteristics at the position of the left ear of the listener 8
in the case of localization and the right ear of the listener 8 in the case of localization of the
sound to the right, and the signal S (t) The position of the ear on the above-mentioned side with
respect to the listener 8 when the speaker (that is, the speaker 4 when the sound is localized to
the left and the speaker 6 when the sound is localized to the right) The FIR filters 11 and 12
perform processing to equalize the characteristics of the signal. The second difference is that the
difference between the amplitude frequency characteristics of both ears of the listener 8 when
the signal S (t) is processed by the FIR filters 11 and 12 is output from the speakers 4 and 6 is
the signal S. The FIR filters 11 and 12 perform processing to equalize the difference between the
amplitude frequency characteristics of both ears of the listener 8 when (t) is output from the
speaker 27.
[0053] Next, in the second embodiment of the present invention, a method for localizing the
sound to the left side of the listener 8 using the speakers 4 and 6 placed in front will be
described using FIG.
[0054] The difference from the embodiment in FIG. 2 is that the impulse responses of the FIR
filters 11 and 12 are h'L (T) and h'R (t), respectively. The impulse response from the oscillator 11 to the position of the left ear of the listener 8 when the signal S (t) is processed by the FIR
filters 11 and 12 is output from the speakers 4 and 6 is L (t). The impulse response from the
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oscillator 1-1 to the position of the right ear of the listener 8 is R (t).
[0055] In such a configuration, from the signal S (t) to the position of the left ear of the listener 8
when the impulse response L (t) and the signal S (t) are output from the speaker 4 without
passing through the FIR filter 11 To make the impulse response h1 (t) equal,
[0057] However, it must be fulfilled. Further, the difference between the amplitude frequency
characteristics of the impulse responses L (t) and R (t) is an impulse from the signal S (t) when
the signal S (t) is output from the speaker 27 to the position of both ears of the listener 8 To be
equal to the difference in amplitude frequency characteristics between the two ears of the
response
[0059] However, it must be satisfied (where F represents the Fourier transform and represents
the transform from the time domain to the frequency domain). Also, the impulse response R (t) at
this time is
[0061] It is derived from (Equation 14) that (Here, F-1 represents an inverse Fourier transform,
and indicates a transform from the frequency domain to the time domain. ) And the impulse
response L (t) is
[0063] The impulse response R (t) is
[0065] As expressed by the equation (13) and the equation (16),
[0067] From (Equation 15) and (Equation 17),
[0069] Thus, satisfying Eq. 13 and Eq. 15 is equivalent to fulfilling Eq. 18 and Eq.
[0070] That is, in the second embodiment, in order to make the listener 4 be able to hear from
the left side by using the speakers 4 and 6, h ′ L (sixteen and eighteen) is satisfied. T), h'R (t)
may be determined.
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[0071] As described above, by realizing the interaural amplitude frequency characteristic
difference of the head transfer function of the listener when the sound source is present on the
left side with the two front speakers, the surround signal is generated from the left side to the
listener. It can be made to hear, and at the same time, the main signal is localized forward by
making the transfer function to the left ear of the listener at that time equal to the transfer
function from the front speaker to the left ear of the listener It is possible to eliminate the
difference in sound quality with the surround signal localized on the left side and the left side. In
other words, the surround signal can be localized to the left side of the listener without degrading
the sound quality, and the sound quality is equivalent to that of the main signal localized to the
front, so a more natural sense of spread and presence can be obtained. be able to.
[0072] In the above embodiment, the surround signal is localized to the left side with respect to
the listener, but in the case of localization to the right, similarly,
[0075] However, h ′ L (T) and h ′ R (t) may be determined so that the equations (20) and (21)
are satisfied.
[0076] Next, a third embodiment of the present invention will be described with reference to the
drawings. The difference from the second embodiment is in the FIR filters 11 and 12 in FIG. That
is, when the signals S (t) are processed by the FIR filters 11 and 12 are output from the speakers
4 and 6, the sound wave arrival time difference and the sound wave arrival level difference
between both ears of the listener 8 are the signal S (t). The FIR filters 11 and 12 perform
processing to be equal to the sound wave arrival time difference and sound wave arrival level
difference between both ears of the listener 8 when output from the speaker 27.
[0077] Next, in the third embodiment of the present invention, a method of localizing sound to
the left side of the listener 8 using the speakers 4 and 6 placed in front will be described using
FIG.
[0078] The difference from the embodiment in FIG. 4 is that the impulse responses of the FIR
filters 11 and 12 are h′′L (T) and h′′R (t), respectively. As in the second embodiment, an
impulse response from the oscillator 1-1 to the position of the left ear of the listener 8 when the
signal obtained by processing the signal S (t) by the FIR filters 11 and 12 is output from the
speakers 4 and 6 Let L (t) be the impulse response from the oscillator 1-1 to the position of the
right ear of the listener 8 R (t).
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[0079] In such a configuration, from the signal S (t) to the position of the left ear of the listener 8
when the impulse response L (t) and the signal S (t) are output from the speaker 4 without
passing through the FIR filter 11 To make the impulse response h1 (t) equal,
[0081] However, it must be fulfilled. In addition, the difference in peak time and the difference in
peak level of each of the impulse responses L (t) and R (t) are obtained from the signal S (t) when
the signal S (t) is output from the speaker 27 to both listeners 8 In order to be equal to the time
difference τ between the peaks of both impulses of the impulse response up to the position of
the ear and the difference α between the peak levels,
[0083] However, it must be fulfilled. (Here, τ is the arrival time to the left ear when the signal S
(t) is output from the speaker 27 minus the arrival time to the right ear, and α is the arrival level
to the right ear as the left ear Divided by the arrival of Generally, when the speaker 27 is on the
left side, τ ≦ 0 and α ≦ 1. ) And the impulse response L (t) is
[0085] The impulse response R (t) is
[0087] Since it is expressed by (Equation 22) (Equation 24),
[0089] From (Equation 23) and (Equation 25),
[0091] Thus, satisfying Eq. 22 and Eq. 23 is equivalent to satisfying Eq. 26 and Eq. 27.
[0092] That is, in the third embodiment, in order to use the speakers 4 and 6 to allow the listener
8 to hear from the left side, h′′L T), h′′R (t) may be determined.
[0093] As described above, by realizing the sound wave arrival time difference and the sound
wave arrival level difference between the listener's both ears when the sound source is present
on the left side, the surround signal is generated from the left side to the listener by realizing the
front two speakers. It can be made to hear, and at the same time, the main signal is localized
forward by making the transfer function to the left ear of the listener at that time equal to the
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transfer function from the front speaker to the left ear of the listener It is possible to eliminate
the difference in sound quality with the surround signal localized on the left side and the left
side. In other words, the surround signal can be localized to the left side of the listener without
degrading the sound quality, and the sound quality is equivalent to that of the main signal
localized to the front, so a more natural sense of spread and presence can be obtained. be able to.
[0094] In the above embodiment, the surround signal is localized to the left side with respect to
the listener, but in the case of localization to the right, similarly,
[0097] However, h′′L (T) and h′′R (t) may be determined so as to satisfy the equations (28)
and (29).
[0098] In the first, second, and third embodiments, when a surround signal is used as a sound
signal and reproduced from a speaker disposed in front of the listener, the sound is heard from
the side or rear of the listener As described above, the amplitude and delay time are adjusted by
the adjustment means, but not limited to the surround signal, for example, a general recorded
sound signal is used as the sound signal, regardless of the arrangement position of the speaker,
any position It may be used as a device that can hear sounds from
[0099] As described above, according to the present invention, since the listener feels that the
surround signal etc. comes from the side or back of the listener, it is possible to use two or more
speakers arranged in front of the listener. By adjusting the amplitude and delay time of the sound
in the listener's both ears, it becomes possible to obtain an acoustic effect similar to that in the
case where the speaker is actually arranged laterally or rearward to emit the sound.
[0100] Further, during the adjustment, the sound quality is degraded by adjusting the transfer
function to the ear closer to the direction in which the sound arrives to the listener so that it is
equal to the transfer function from the speaker to the above-mentioned ear of the listener. It can
be localized to the side or back of the listener.
[0101] In addition, it becomes possible to obtain a realistic sound effect by combining with the
main signal, and the sound quality of the sound localized at that time or side at that time is the
same as that of the main signal localized forward. You can get a more natural feeling of spread
and presence.
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