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JP2008098826

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP2008098826
A sound that can localize two sound sources at different positions even on a straight line
connecting two sets of speakers, and localize two sound sources at different positions within an
extremely wide range centered on a sound reproduction device. Provision of playback equipment.
SOLUTION: Two sets of reproduction units 20 and 30 to which signals of two channels are
respectively inputted are respectively constituted by even number of speakers 20a and 20b and
30a and 30b, and one of the groups constituting one set of reproduction units By inverting the
signal input to the speaker of the part by the phase inverter 50, the directivity characteristic of
the reproduction unit is deformed, and the sound sources of the two channels are localized at
different positions. [Selected figure] Figure 1
Sound reproduction apparatus and sound reproduction method
[0001]
The present invention relates to an audio reproduction apparatus and an audio reproduction
method which are used, for example, in a teleconference and in which an audible band signal of
two channels is reproduced by a plurality of speakers.
[0002]
A sound reproducing apparatus for amplifying and reproducing a two-channel audible band
signal used in a teleconferencing system or a teleconferencing system with a plurality of
speakers makes a difference in signals output from a plurality of speakers, thereby enabling the
position of the sound image that the listener can hear. It can be changed.
09-05-2019
1
By localizing a plurality of reproduced sound images at different positions, it becomes possible to
increase the intelligibility of each sound source. Non-Patent Document 1 discloses one of the
methods of localizing the sound image at different positions and enlarging the listening position
as described above. The prior art will be described with reference to FIG. Two speakers SL1 and
SL2 and SR1 and SR2 are respectively installed at left and right speaker positions to which two
channel input signals Ch.1 and Ch.2 are respectively input. The directivity of the speakers SL1
and SR1 located outside in each pair of speakers is directed in the front direction, and the
directivity of the speakers SL2 and SR2 located inside is directed to the listener B located in front
of the center of the two pairs of speakers It is done.
[0003]
The listener A located in front of the left speaker SL1 hears the sounds of the speaker SL1 and
the speaker SR2. Since the distance between the listener A and each of the speakers SL1 and SR2
is longer in the speaker SR2, the delay unit 70L is connected in series to the input side of the
speaker SL1 and the above-mentioned distance is transmitted during the time when the sound is
transmitted. Signal Ch. 2 is delayed by delay device 70L. Also, an amplifier 72R is connected in
series to the input side of the speaker SR2 far from the listener A so as to make the listener A
hear the sound of the speaker SL1 and the sound of the speaker SR2 with the same magnitude.
Ru. By doing this, it is possible to obtain good sound image localization even for the listener A
who is located in front of the left speaker SL1. The conventional localization can be obtained
because the listener B located at the center of the two pairs of speakers listens simultaneously to
the sounds of the speakers SL2 and SR2 which are not delayed from each other. The delay device
70L and the corresponding delay device 70R are connected in series to the input side of the
speaker SR1, and the amplifier 72R and the corresponding amplifier 72L are connected in series
to the input side of the speaker SL2. Therefore, the listener C located in front of the right speaker
SR1 hears the sounds of the speaker SR1 and the speaker SL2, and good sound image
localization can be obtained on the same principle as the listener A side. Thus, the listening area
can be enlarged in the direction parallel to the arrangement direction of the speakers.
[0004]
Another method for expanding the listening position is shown in Non-Patent Document 2.
Another prior art will be described with reference to FIG. This method does not localize the sound
image between the speaker L and the speaker R, but reproduces the input sound signal of Ch. 1
09-05-2019
2
from the speaker R and the sound signal of Ch. 2 from the speaker L, respectively. For this
purpose, when the signals are mixed in both channels Ch. 1 and Ch. 2, crosstalk canceller 80 is
used to remove it. Therefore, in this method, the respective sound sources of Ch. 1 and Ch. 2 to
be input are fixed to the position of either speaker L or R and reproduced.
[0005]
In these prior arts, the listening area can be expanded in a direction parallel to the direction in
which the speakers are arranged. Jiro Oga, Yoshio Yamazaki, Yutaka Kanada "Sound System and
Digital Processing" 1995, pp. 232-233 Takahiro Oyama, Haruhide Hokari, Shoji Shimada
"Comparison of sound source separation methods used for multiple listeners-enabled voice
communication", Journal of the Institute of Electronics, Information and Communication
Engineers (A), Vol. J86-ANo. 7, 2003
[0006]
However, in the conventional method, when the listener is located near the extension of the line
connecting the two sets of speakers, the view angle of the two sets of speakers is narrowed from
the position of the listener, and good sound image localization can be obtained. It becomes
impossible. That is, the listener on the extension of the line connecting the two sets of
loudspeakers hears the channel signal from the two sound sources from the same direction. This
invention is made in view of such a subject, and even if the listener on the extension of the
straight line which connects two sets of speakers can also localize the sound image to two sound
sources to a different position. It aims at providing an apparatus and a sound reproduction
method.
[0007]
The sound reproducing apparatus according to the present invention comprises two sets of
reproducing units separated from each other, and at least one of the reproducing units comprises
an even number of speakers whose sound emitting side is directed outward. The speakers in each
reproduction unit consisting of one even number of speakers are arranged symmetrically with
respect to a straight line connecting the centers of the respective sets. Furthermore, a phase
inverter is provided to invert the phase of the input channel signal input to some of the speakers
constituting the reproduction unit of the even number one speaker.
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[0008]
According to the sound reproducing apparatus of the present invention, to a listener located on
both sides with respect to the sound reproducing apparatus on an extension of a straight line
connecting two sets of speakers, the channel signal is input from the unit without phase
inversion. The sound image of the emitted sound is localized and heard by the reproduction unit,
and the sound image of the sound emitted from the reproduction unit into which the channel
signal is phase-reversed and input is localized and heard to the left or right of the listener. As
described above, conventionally, even for a listener at a position where the sound of channel
signals from two sound sources can be heard from the same direction, the sound images of the
two sound sources are localized at different positions. You can easily distinguish whether you are
listening to the playback sound from.
[0009]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings. The same reference numerals are given to the same components in the drawings, and
the description will not be repeated.
[0010]
The configuration of a first embodiment of the sound reproduction device according to the
present invention is shown in FIG. This sound reproduction apparatus is used, for example,
disposed on an oblong conference table 10. In the sound reproducing apparatus according to the
first embodiment, an even number of speakers for reproducing one input channel signal Ch. 1
are separated from one reproduction unit 20 disposed with the sound emission side facing
outward and one reproduction unit. And another reproduction unit 30 for reproducing the other
input channel signal. In the case of the first embodiment, the two sets of reproduction units 20
and 30 have the same configuration, and are an example configured of two speakers 20a and
20b and two speakers 30a and 30b. The speakers 20a and 20b, 30a and 30b of the two sets of
reproduction units 20, 30 are arranged symmetrically with respect to a straight line 40
connecting the centers of the respective sets, and the reproduction units 20 and 30 are at the
middle point of the line 40. They are arranged at symmetrical positions.
09-05-2019
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[0011]
Furthermore, a phase inverter 50 is provided which inverts the phase of the input channel signal
inputted to a part of the speakers constituting one of the two reproduction units 20 and 30. In
the case of the first embodiment, the phase inversion unit 50 inverts the phase of the input
channel signal Ch. 1 input to the speaker 20 a constituting the reproduction unit 20. Hereinafter,
the speaker to which the phase-inverted signal is input is hatched in the drawing. The phase
inverter 50 does not have to be arranged on the conference table 10. Thus, for example, three
listeners A, B, and C each and listeners E, F, and G on both sides of the straight line 40 around the
conference table 10 on which the sound reproducing apparatus of the first embodiment is
arranged on a desk. However, the listeners D and H are located at each end of the straight line 40
in the direction of extension.
[0012]
In the first embodiment, when signals of different sound sources are input to the input channel
signals Ch. 1 and Ch. 2, the sound of the input channel signal Ch. 2 reproduced from the
speakers 30a and 30b of the reproduction unit 30 is received. Also from the listeners A to H, the
sound image is localized and listened to at the position of the reproduction unit 30. The sound of
the input channel signal Ch. 1 reproduced from one reproduction unit 20 is from the listeners A,
B, C and the listeners E, F, G at positions on both sides of the straight line 40 in the reproduction
unit 20. The sound image is localized and listened to the position. On the other hand, although
the principle will be described later, in the listeners D and H located on the extension of the
straight line 40, the sound of the input channel signal Ch.2 is a sound image in the direction of
either the listener D or H ear. Is localized and listened.
[0013]
That is, for the listeners D and H located in the extension direction of the straight line 40, which
can not obtain good sound image localization with the prior art, the input channel signal Ch. The
sound image of the sound can be localized in one of the left and right ears of the listeners D and
H, and the sound image of the sound of the input channel signal Ch. 2 reproduced from the
reproduction unit 30 is the position of the reproduction unit 30 Can be localized. Also, from the
listener located on both sides of the straight line 40 connecting the two reproduction units 20
and 30, the position of the reproduction units 20 and 30 are widely separated from each other as
09-05-2019
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in the conventional sound reproduction apparatus, so the input channel The sound of the signal
Ch. 1 is localized at the position of the reproduction unit 20, and the sound of the input channel
signal Ch. In this embodiment, the sound images of the two sound sources can be localized at
different positions with respect to the listeners located all around the sound reproduction
apparatus in this way, and the signals from both of these sound sources can be easily It can be
distinguished.
[0014]
[Principle of Localizing Sound in an Extension Line Direction of the Straight Line 40] FIG. 2
shows directional characteristics of sound of the speakers 20a and 20b which constitute the
reproduction unit 20 of the first embodiment. The horizontal axis is a straight line 40 connecting
the centers of the reproduction units 20 and 30 described above, and is a view schematically
representing horizontal directional directivity characteristics 41a and 41b of the sound pressure
emitted from the speakers 20a and 20b. The input channel signal Ch.1 phase-inverted by the
phase inverter 50 is input to the speaker 20a with respect to the speaker 20b to which the input
channel signal Ch.1 is input as it is. Sound pressure areas are equal to each other with respect to
the direction of 0 degrees and 180 degrees which are equal to each other to cancel each other so
that the sound pressure becomes zero.
[0015]
When a certain place in the silent area 42, 43 is captured, the sound pressures whose phases are
reversed cancel each other. However, since the human head has a certain size and both ears are
located apart to the left and right, a subtle sound pressure difference occurs and the sound can
be heard. For example, when the listener D located in the silent area 42 faces in the direction of
either of the speakers 20a or 20b or tilts the head and listens, the user hears the sound with only
one ear in the listening direction. It becomes single ear listening. In the case of single ear
listening, the sound from that direction is heard loud, so it is felt that the sound can be heard
from that direction, that is, the direction different from the direction of the reproduction unit 20.
In other words, if the face is facing the front and you listen to it with your right ear, for example,
you can hear the sound from the direction of the right shoulder. If you hear it with your left ear,
you feel like you can hear the sound from the direction of your left shoulder. Therefore, for the
listener located in the silent area, the sound of the reproduction unit 30 to which the input
channel signal Ch. 2 is input is localized at the position of the reproduction unit 30 and the input
channel Ch. 1 is input. The sound of the playback unit 20 can be localized in the direction of
either the left or right ear. That is, it can be easily distinguished whether the sound being heard is
09-05-2019
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the input channel signal Ch.1 or Ch.2. Therefore, the generated sound sources of the two channel
signals can be easily distinguished.
[0016]
As is apparent from the above description, the sound image direction of the reproduced sound of
the input channel signal Ch. 1 that produces the silent area is easily changed depending on the
posture and position of the listener in the silent areas 42 and 43. The sound image can be
localized at a position other than the direction of the reproduction unit 20. On the other hand,
the sound image of the reproduction sound of the reproduction unit 30 is localized at the
position or direction of the reproduction unit to the listeners in the silent areas 42 and 43.
Therefore, even the listeners located in the silent areas 42 and 43 can easily separate the
positions of the sound image localization of the two sound sources.
[0017]
In the sound reproduction apparatus according to the present invention, at least one
reproduction unit needs to be configured by an even number of speakers. From this point, in
order to miniaturize the sound reproduction device, it is preferable that the outer diameter of the
speaker be small. However, with a small diameter speaker, there is a problem that low frequency
sound can not be reproduced sufficiently. In addition, since the low frequency sound is weak in
straightness and is radiated all around the speaker, low frequency sound is particularly
insufficient when the speaker of the reproduction unit 20 is reproduced in reverse phase as in
the first embodiment. That is, since the low sound emitted from the speakers 20a and 20b in FIG.
2 also wraps around the back of the speaker, the low sounds cancel each other.
[0018]
As described above, for example, in an audio reproduction apparatus used for a teleconference
system, when reproducing a sound signal, it is difficult to localize a sound image of sound in a
band lower than a certain band. On the other hand, humans have an advance sound effect that
recognizes the direction of the sound heard earlier. Therefore, in the second embodiment, by
utilizing these phenomena, the insufficient bass of the sound localized by the reproduction units
20 and 30 is compensated.
09-05-2019
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[0019]
As shown in FIG. 3, in the second embodiment, the low frequency speaker 60 is disposed
between the reproduction units 20 and 30. On the other hand, the signals of the input channel
signals Ch. 1 and Ch. 2 are combined by the mixer 62, the low pass filter 64 extracts the low
frequency signal from the output signal thereof, and the output signal of the low pass filter 64 is
The low frequency signal delayed by the delay 66 is input to the low frequency speaker 60.
[0020]
When the cutoff frequency of the low pass filter 64 is, for example, 600 Hz, it is known that the
same sound image as the sound image determined by the preceding sound from the reproduction
unit 20 or 30 can be heard. Further, the lower limit value of the delay time is determined from
the range in which the preceding sound effect can be obtained. If the delay time is at least about
630 μs to about 1 ms, the sound image of the sound from the low frequency speaker 60 is
localized at the sound image position of the sound radiated first. Thus, the delay time for
obtaining the preceding sound effect is a relatively short time. On the other hand, if the delay
time exceeds 20 ms, human beings recognize the sound from the low-range speaker 60 as echo
sound, that is, it recognizes it as another sound, so the upper limit of the delay time needs to be
20 ms or less .
[0021]
The report on the relationship between the preceding sound and the cutoff frequency of the lowpass filter can be found in the reference "Uematsu Hisashi et al.," Expansion of listening position
of stereo sound using the preceding sound effect of center speaker ", Proceedings of the
Acoustical Society of Japan It is described in September, 2005, pp. 565-566. The preceding
sound effect is also called the first wavefront law, and is described, for example, in the reference
document "J. Brauert et al., "Spatial Acoustics", published by Kajima Publishing Co., Ltd., July,
1987, p. 142 ", and the threshold for feeling echo sound is also described in Table 4.2, p. 148 of
the same document. . From the above, the cutoff frequency of the low pass filter 64 may be 600
Hz or less, and the delay time of the delay may be set in the range of 1 to 20 ms.
[0022]
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8
With this configuration, it is possible to compensate for the bass of the sound localized by the
reproduction units 20 and 30 without affecting the sense of localization. The low-range speaker
60 may be disposed between the reproduction units 20 and 30, and strictness in the position to
be disposed is not required. This can be explained by the fact that the minimum delay time to
obtain the preceding sound effect is 1 ms. For example, assuming that the sound velocity is 340
m / sec, the delay time 1 ms is 34 cm when converted to distance. If the position of the low-range
speaker 60 is close to the 34 cm listener for the distance between each listener and the playback
units 20 and 30, the effect of the delay time disappears, and the preceding sound effect is
obtained. It disappears. That is, it is preferable that the distance between the listener and the low
frequency speaker is not shorter than 34 cm or more than the distance between the listener and
the reproduction unit.
[0023]
This will be described with reference to FIG. When the low band speaker 60 is disposed at the
exact middle position of the reproducing units 20 and 30 as shown by the broken line in FIG. 1,
the distance between the low band speaker 60 and the listener B located in front is the most It
becomes short. For example, it is assumed that the listeners A, B, and C are spaced 60 cm apart
and sit 1 m apart in the direction orthogonal to the arrangement direction of the reproduction
units. In this case, the distance between the reproduction units 20 and 30 and the listener B is
about 1.2 m. At this time, since the distance between the listener B and the low frequency range
speaker 60 is 1.0 m, it is only 20 cm shorter than the distance between the listener B and the
reproduction units 20 and 30. Therefore, the sound emitted from the reproduction units 20 and
30 reaches the listener B first because the above conditions are satisfied. As a result, the sense of
localization is determined by the sounds emitted from the reproduction units 20 and 30.
[0024]
As described above, even at the position of the low-range speaker under the worst condition, the
preceding sound effect by the sound from both the reproduction units 20 and 30 can be
obtained. Therefore, if the low-range speaker 60 is arranged in the same row as the reproduction
units 20 and 30, It may be placed anywhere in between. Of course, if the reproduction units 20
and 30 are placed further apart, the distance between the low frequency speaker 60 and the
listener may be 34 cm or more shorter than the distance to the reproduction unit. In that case,
the delay time of the delay unit 66 may be increased within the range of 1 to 20 ms. Although
09-05-2019
9
one low frequency speaker 60 is shown, the sound in the low frequency band is poor in
rectilinearity as described above, and it is sufficient for one to go around the back of the speaker.
In addition, the low-range speaker 60 may be a non-directional speaker, or two sound emitting
sides may be provided outside in the same manner as the reproduction units 20 and 30.
[0025]
FIG. 4 shows a third embodiment of the present invention in which four speakers constitute the
respective reproduction units 20 and 30. In FIG. The four speakers 20a, 20b, 20c and 20d of the
reproduction unit 20 'are arranged so that the radiation direction of the sound is a radial pattern
with equal angular intervals, and the speaker 20a 20b and the speakers 20c and 20d are in line
with the straight line 40. Are arranged symmetrically. The four speakers 30a, 30b, 30c, and 30d
of the reproduction unit 30 'are also arranged and configured in the same manner as the
reproduction unit 20'. The input channel signal Ch.1 phase-inverted by the phase inverter 50 is
input to all the speakers on one side of the straight line 40 of one reproduction unit 20 'and the
two speakers 20a and 20b. The input channel signal Ch. 2 is input to all the speakers 30 a to 30
d in the same phase with respect to the reproduction unit 30 ′. Although FIG. 4 shows an
example using the low band speaker 60, this may be omitted.
[0026]
The directional characteristics of the sound of the reproduction unit 20 'of the third embodiment
are shown in FIG. In the case of the third embodiment, one side sandwiching the straight line 40
is configured by two speakers each, and the four speakers are arranged radially with the sound
emission side facing outside, so the silent area described in FIG. 2 The range of 42 and 43
becomes narrower than that of FIG. In other words, the arrival angle range of the sound from the
reproduction unit is expanded. Therefore, the third embodiment is effective when the conference
table is long in the extension direction of the straight line 40.
[0027]
Furthermore, the output signal of the phase inverter 50 may be supplied to non-adjacent
speakers in the reproduction unit 20 '. For example, in the reproduction unit 20 ', an input
channel signal Ch. 1 whose phase is inverted by the phase inverter 50 is input to, for example,
the speakers 20a and 20c. In this way, the directivity shown in FIG. 6 is obtained with respect to
09-05-2019
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the directivity shown in FIG. That is, the silent areas 44 and 45 can be generated in the direction
orthogonal to the straight line 40, that is, in the direction of 90 degrees and 270 degrees at the
position of the center of the reproducing unit 20 '. As a result, for the listener located in the silent
area 42, 43, 44, 45, the sound from the reproduction unit 20 'is clearly different from the sound
image of the reproduction sound from the other reproduction unit 30' whose phase is not
reversed. The sound image can be localized.
[0028]
In this case, it is not necessary for the listener located originally in the direction of the silent
regions 44 and 45 to generate the silent region in the direction orthogonal to the straight line 40
because the view angle with respect to both the reproducing units 20 'and 30' is large. I feel like
that. However, the listener E located in the silent area 44 in the 90 ° direction takes a posture to
listen to the sound from the speaker 20 a located on the left side, so that the sound image of the
sound of the reproduction unit 20 ′ is the listener E The sound image of the sound of the
reproduction unit 30 'is localized at the position of the reproduction unit 30'. In this way it is
possible to make the distinction between the two channels of sound clearer.
[0029]
Although the number of speakers constituting each of the reproduction units 20 and 30 has been
described as two to four in the above description, the configuration of the first to third
embodiments described above may be used even if six or more even number speakers are used.
It is possible to achieve the same effect. Further, although the explanation has been made by
showing an example in which the number of speakers constituting the reproducing units 20 and
30 is the same, one reproducing unit 30 may be constituted by one speaker as shown in FIG. The
listeners in this case are five persons A, B, C located on the sound emitting side of the speaker 30
b of the reproduction unit 30 with respect to the straight line 40 and the listeners D, H located at
both ends of the straight line 40. It is needless to say that the same effect can be obtained even if
the configurations of the reproducing units 20 and 30 are reversed.
[0030]
As described above, the sound reproduction method in which the phase input to a part of the
speakers constituting one of the reproduction units of the two sets is inverted is also possible on
the straight line connecting the two sets of speakers, The two sound sources can be localized at
different positions, the sound images of the two sound sources are localized at different positions
09-05-2019
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in a very wide range around the sound reproducing apparatus, and the reproduced sound from
any sound source can be heard. You can easily distinguish them.
[0031]
BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows the structure of Example 1 of
the sound reproduction apparatus of this invention.
FIG. 6 is a diagram showing directional characteristics of sound of speakers 20 a and 20 b
constituting the reproduction unit 20 of the first embodiment. The figure which shows the
structure of Example 2 of the sound reproduction apparatus of this invention. The figure which
shows the structure of Example 3 of the sound reproduction apparatus of this invention. FIG. 16
is a diagram showing directional characteristics of sound of the reproduction unit 20 of the third
embodiment. The figure which shows the directional characteristic of the speaker at the time of
not supplying the output signal of the phase inverter 50 to the adjacent speaker which comprises
a reproduction | regeneration unit. The figure which shows the example which comprised one
reproduction | regeneration unit of the sound reproduction apparatus of this invention by one
speaker. The figure which shows the prior art disclosed by the nonpatent literature 1. FIG. The
figure which shows the prior art disclosed by the nonpatent literature 2. FIG.
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