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DESCRIPTION JP2008060939

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DESCRIPTION JP2008060939
The present invention provides an audio apparatus which can clearly hear conversation contents
even in a conference participant who exists around the apparatus, in particular even a conference
participant who exists in a direction other than the front of the speaker. An audio signal input
from the outside is directly input to a subsequent stage (speaker), and is input to a phase shift
circuit 221 and a signal inverting circuit 222A. The output signal of the phase shift circuit 221 is
input to the subsequent stage, and is input to the signal inverting circuit 222B. Output signals of
the signal inverting circuit 222A and the signal inverting circuit 222B are input to the
subsequent stage. The phase shift circuit 221 is composed of an FIR filter or the like, performs
phase shift operation in the entire frequency band, and shifts the phase of the audio signal by 90
degrees. The signal inverting circuit 222A and the signal inverting circuit 222B invert the input
signal (that is, shift the phase by 180 degrees). Loudspeakers are placed on the side of the diskshaped casing, shifted by 90 degrees. [Selected figure] Figure 5
Sound equipment
[0001]
The present invention relates to an audio device used for an audio conference, and more
particularly to an audio device provided with a plurality of speakers.
[0002]
BACKGROUND In order to conduct an audio conference (communication conference) at a remote
place, an audio conference apparatus integrally provided with a speaker and a microphone has
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become widespread.
The audio conference apparatus transmits the sound collected by the microphone to the
connection destination, and emits the sound received from the connection destination from the
speaker. When a conference is conducted by a plurality of people, such an audio conference
device is often installed at the center of the conference participants (the center of the conference
desk, etc.). Therefore, it is desirable that such an audio conference apparatus be miniaturized,
and for example, as shown in Patent Document 1, there is proposed an audio conference
apparatus which is miniaturized by omitting a speaker box.
[0003]
Also, since the audio conference apparatus is configured to have a speaker and a microphone in
the same space, when the voice received from the connection destination is released from the
speaker, this voice is collected by the microphone and transmitted to the connection destination. ,
Echo and other noises. Therefore, as shown in Patent Document 2, in an audio conference
apparatus having an echo canceller function, an audio conference apparatus is proposed in which
a microphone is accommodated at the tip of a cylindrical elastic body and acoustic coupling
between a speaker and the microphone is suppressed. There is. JP-A-8-204803 JP-A-8-298696
[0004]
However, in the devices described in Patent Documents 1 and 2, the speaker can not listen
clearly to the content of the utterance because the speaker faces upward in the housing and does
not face in the direction of the conference participants present around the device. . That is, while
the voice in the low frequency band has low straightness and tends to wrap around easily, the
voice in the high frequency band has high straightness and is hard to wrap around, so in regions
other than the speaker front direction, each frequency band There was a problem that the
volume difference between the two was so large that it was difficult to hear the contents of the
conversation.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to provide an audio
apparatus which can clearly hear conversation contents even in a conference participant who
exists around the apparatus, in particular even a conference participant who exists in a direction
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other than the front of the speaker.
[0006]
The acoustic device according to the present invention is arranged on a circumference centered
on one axis, and has a plurality of speakers installed in the radial direction of the circumference
in a projection projected on a plane orthogonal to the axis; An audio apparatus comprising: an
audio signal processing unit for supplying audio signals to be emitted to the plurality of speakers,
wherein the audio signal processing unit is configured to generate a phase of an audio signal to
be supplied to each speaker. After being rotated according to the angle of the installation
position on the circumference, the speaker is supplied with each of the speakers.
[0007]
In this configuration, a plurality of speakers are installed on a circumference centered on an axis.
Each speaker is installed in a direction normal to the circumference (for example, when the case
is a disk, obliquely downward when viewed from the side of the case) in a projection projected
onto a plane orthogonal to this axis.
The audio signals supplied to these speakers are rotated according to the installation position
(angle on the circumference) of each speaker. Thus, for example, at the positions between the
speakers, the phase of the sound coming from the speakers on both sides is shifted, so that only
the low band is not intensified, and the volume change for each frequency band is small. be able
to.
[0008]
The present invention is further characterized in that the center of the second circumference is
arranged on a second circumference that is centered on the axis and smaller in diameter than the
circumference and is projected onto a plane orthogonal to the axis. It further comprises a
plurality of microphones installed facing in a direction.
[0009]
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In this configuration, a plurality of microphones and speakers are respectively installed on the
circumference centered on the same axis.
The microphone is placed inside the speaker in the direction opposite to the directivity of the
speaker. Therefore, it is possible to suppress the sound coming from the speaker into the
microphone.
[0010]
Further, according to the present invention, four of the plurality of speakers are provided at a
central angle of 90 degrees on the circumference, and the audio signal processing unit is
configured to transmit the phases of audio signals supplied to the respective speakers. It is
characterized by rotating by 90 degrees.
[0011]
In this configuration, the speakers are arranged with their central angles shifted by 90 degrees.
Further, the phase of the audio signal supplied to each speaker is shifted by 90 degrees. Thus, on
the front of each speaker, the sound coming from the speakers on both sides cancel each other,
and only the sound coming from the front speaker can be clearly heard.
[0012]
According to the present invention, since the phase of the sound coming from the speakers on
both sides is shifted at the positions between the speakers, only the low band is not strengthened,
and the volume change for each frequency band is small. Can be heard clearly.
[0013]
An audio conference system according to an embodiment of the present invention will be
described with reference to the drawings.
FIG. 1 is an external view of the audio conference apparatus according to this embodiment,
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wherein FIG. 1 (A) is a plan view and FIG. 1 (B) is a side view. In the figure, the direction of the
microphone 10A and the speaker SP1 is 0 ° with the center position of the audio conference
apparatus 1 viewed from the top as the center of rotation, and the angle increasing
counterclockwise is θ. FIG. 2 is a block diagram showing the configuration of the voice
conference device.
[0014]
The audio conference device 1 is provided with a disk-shaped case 11. The housing 11 has a
circular shape with a diameter of about 30 cm when viewed from the top. The area of the upper
surface and the lower surface of the housing 11 is smaller than the area of the midway portion in
the vertical direction. The housing 11 has a shape viewed from the side, which narrows from the
predetermined position in the height direction toward the upper surface, and narrows toward the
lower surface. That is, the housing 11 has a shape having inclined surfaces on the upper side and
the lower side from the predetermined position. A recess 12 is formed on the upper surface of
the housing 11, and the area of the recess 12 as viewed from the upper surface is smaller than
the area of the upper surface of the housing 11. In addition, the recess 12 has a depth in which
the microphone can be embedded. The central position of the recess 12 coincides with the
central position of the upper surface.
[0015]
The sixteen microphones 10 </ b> A to 10 </ b> P are disposed on the side surface of the recess
12 (inside the upper surface of the housing 11). The respective microphones 10A to 10P are
arranged at equal angular pitches (in this case, at intervals of about 22.5 °) with the center
position of the housing 11 as the center of rotation when viewed from the top. At this time, the
microphones 10A are in the θ = 0 ° direction, and the microphones 10A to 10P are arranged
along the direction in which θ increases by 22.5 ° in order. For example, the microphone 10E
is disposed in the θ = 90 ° direction, the microphone 10I is disposed in the θ = 180 °
direction, and the microphone 10M is disposed in the θ = 270 ° direction. Further, each of the
microphones 10A to 10P has single directivity, and each has strong directivity in the central
direction when viewed from the top. For example, the microphone 10A has directivity in the θ =
180 ° direction, the microphone 10E has directivity in the θ = 270 ° direction, and the
microphone 10I has directivity in the θ = 0 (360) ° direction, The microphone 10M has
directivity in the θ = 90 ° direction. The number of microphones is not limited to this, and may
be appropriately set according to the specification.
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[0016]
The four speakers SP <b> 1 to SP <b> 4 are installed on the inclined surface on the lower side of
the housing 11. The speakers SP1 to SP4 are arranged at equal angular pitches (in this case,
approximately 90 ° in this case) with the center position of the housing 11 as the center of
rotation when viewed from the top. The speaker SP1 is arranged in the same θ = 0 ° direction
as the microphone 10A, the speaker SP2 is arranged in the same θ = 90 ° direction as the
microphone 10E, and the speaker SP3 is arranged in the same θ = 180 ° direction as the
microphone 10I. The speaker SP4 is disposed in the same θ = 270 ° direction as the
microphone 10M. Due to these arrangements, the speaker SP1 emits sound in the direction of θ
= 0 °, the speaker SP2 emits sound in the direction of θ = 90 °, and the speaker SP3 emits
sound in the direction of θ = 180 °, The speaker SP4 emits sound in the direction of θ = 270
°.
[0017]
In the audio conference apparatus 1, the sound emission direction and the sound collection
direction of adjacent speakers and microphones (for example, the speaker SP1 and the
microphone 10A) are opposite directions, and the sound emission and sound collection directions
are the same. The microphones (e.g., the speaker SP1 and the microphone 10I) are disposed at
the farthest positions from each other, so the sound coming from the speaker to the microphone
becomes extremely small.
[0018]
The operation unit 13 is installed on an inclined surface on the upper side of the housing 11, and
includes various operation buttons (not shown) and a liquid crystal display panel.
The input / output interface 14 is installed on a slope on the lower side of the housing 11 at a
position where the speakers SP1 to SP4 are not installed, and includes a network connection
terminal (not shown), a digital audio terminal, an analog audio terminal, etc. There is. The voice
conference device 1 can be connected to another device by connecting a network cable or the
like to the input / output interface 14.
[0019]
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In FIG. 2, the audio conference apparatus 1 includes microphones 10A to 10P, speakers SP1 to
SP4, an operation unit 13, an input / output interface 14, a control unit 20, an echo canceller 21,
a speaker signal processing circuit 22, and four D / A converters 23, four sound emission AMPs
(amplifiers) 24, sound collection AMPs (amplifiers) 25A to 25P, A / D converters 26A to 26P, and
a microphone signal processing circuit 27.
[0020]
The control unit 20 performs general control of setting of the voice conference device 1, sound
collection, sound emission and the like, and gives control based on the content of the operation
instruction input by the operation unit 13 to each portion of the voice conference device 1.
[0021]
The microphones 10A to 10P pick up voices from the outside such as the voices of the conferees.
The collected sound AMPs (amplifiers) 25A to 25P amplify the sounds collected by the
microphones 10A to 10P, respectively, and output the amplified sounds to the A / D converters
26A to 26P.
The A / D converters 26A to 26P perform analog-to-digital conversion on the audio signals
amplified by the picked-up AMPs 25A to 25P, respectively, and output the converted signals to
the microphone signal processing circuit 27.
[0022]
The microphone signal processing circuit 27 selects and outputs the signal with the highest
sound pressure level among the audio signals output from the A / D converters 26A to 26P. A
detailed block diagram of the microphone signal processing circuit 27 is shown in FIG. The
microphone signal processing circuit 27 includes adders 271A to 271P, a select / mixing circuit
272, and a maximum signal detection circuit 273. The audio signals A to P are input to the
adders 271A to 271P from the A / D converters 26A to 26P, respectively. Further, adjacent
signals (signals output from microphones corresponding to respective adders) are branched and
input to the adders 271A to 271P. For example, the audio signal A and the audio signal B are
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input to the adder 271A, and the audio signal B and the audio signal C are input to the adder
271B. The adders 271A to 271P add and output the input audio signals. By adding the signals
collected by the adjacent microphones, the signal in the front direction of the microphone is
intensified, and the signal in the other direction is weakened, so that the directivity of the
microphone is improved.
[0023]
The sound pressure levels of the added audio signals are compared in the maximum signal
detection circuit 273. The maximum signal detection circuit 273 compares the sound pressure
levels of the respective sound signals, and as a result, selects the sound signal having the highest
sound pressure level and sets it in the select / mixing circuit 272. The select / mixing circuit 272
selects only the set audio signal and outputs it to the echo canceller 21. Further, the maximum
signal detection circuit 273 may select a plurality of audio signals in order from the audio signal
having the highest sound pressure level and set the selected audio signal in the selection /
mixing circuit 272. In that case, the select / mixing circuit 272 mixes the plurality of audio
signals set and outputs the mixed signal to the echo canceller 21.
[0024]
The signal with the highest sound pressure level or the signal obtained by mixing a plurality of
signals in order from the signal with the highest sound pressure level is output, and other lowlevel signals are not output, so the S / N ratio is improves. In the above configuration, the signals
collected by the adjacent microphones are added and output, but the signals collected by the
respective microphones may be output independently, or two or more adjacent signals may be
added. May be output.
[0025]
An output signal of the microphone signal processing circuit 27 is input to the echo canceller 21.
The output signal of the echo canceller 21 is transmitted to another device via the input / output
interface 14. The input / output interface 14 also outputs voice information (or voice signal)
received from another device to the echo canceller 21. The echo canceller 21 estimates a
wraparound component from the speakers SP1 to SP4 to the microphones 10A to 10P, and
subtracts the estimated wraparound component from the output signal of the microphone signal
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processing circuit 27.
[0026]
A detailed block diagram of the echo canceller 21 is shown in FIG. The echo canceller 21
includes an adaptive filter 211 and an adder 212. The adaptive filter 211 includes a digital filter
such as an FIR filter. The adaptive filter 211 estimates a transfer function of an acoustic transfer
system (sound propagation path from the speaker to the microphone), and calculates filter
coefficients of the FIR filter so as to simulate the estimated transfer function. The adaptive filter
211 generates a simulation signal of a loop-around component from the speaker to the
microphone with the estimated filter coefficient. The simulated signal is subtracted from the
output signal of the microphone signal processing circuit 27 in the adder 212. Therefore, the
output signal of the adder 212 is a signal obtained by removing an interference component from
the signal collected by the microphone.
[0027]
The estimation of the transfer function and the calculation of the filter coefficient are performed
using an adaptive algorithm based on a signal supplied to the speaker using a residual signal
which is a signal output from the adder 212 as a reference signal. The adaptive algorithm is an
algorithm that calculates filter coefficients so that the residual signal is as small as possible.
[0028]
As a result, a signal simulating the wraparound signal of the sound transmission system is
generated in the adaptive filter 211, and only the wraparound signal can be efficiently attenuated
by subtracting the simulation signal from the collected sound signal in the adder 212. Thereby,
the echo canceller 21 can prevent the echo generated by the loop signal. Further, when this voice
conference apparatus is used as a loudspeaker that emits voices picked up by the microphones
10A to 10P through the input / output interface 14 and emitted from the speakers SP1 to SP4,
the echo canceller 21 is generated due to the loop phenomenon of the loop signal. You can also
prevent howling.
[0029]
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An output signal of the echo canceller 21 (a sound signal received from another device) is output
to the speaker signal processing circuit 22. The speaker signal processing circuit 22 branches
and outputs the audio signal input from the echo canceller 21 into four systems. A detailed block
diagram of the speaker signal processing circuit 22 is shown in FIG. The speaker signal
processing circuit 22 includes a phase shift circuit 221 and two signal inverting circuits 222A
and 222B.
[0030]
The audio signal input from the echo canceller 21 is input to the D / A converter 23 as it is, and
is input to the phase shift circuit 221 and the signal inverting circuit 222A. An output signal of
the phase shift circuit 221 is input to the D / A converter 23 and also input to the signal
inverting circuit 222B. The output signals of the signal inverting circuit 222A and the signal
inverting circuit 222B are input to the D / A converter 23.
[0031]
The phase shift circuit 221 is composed of an FIR filter or the like, performs phase shift
operation in the entire frequency band (wide frequency band, for example, several tens Hz to
several kHz), and shifts the phase of the audio signal by 90 degrees. The signal inverting circuit
222A and the signal inverting circuit 222B invert the input signal (that is, shift the phase by 180
degrees).
[0032]
The audio signal whose phase is shifted by 90 degrees by the phase shift circuit 221 is input to
the D / A converter 23. In addition, audio signals whose phases are shifted by 180 degrees by the
signal inverting circuit 222A and the signal inverting circuit 222B are input to different D / A
converters 23, respectively. As a result, audio signals whose phases are shifted by 90 degrees are
input to the four D / A converters 23, respectively. That is, assuming that the audio signal input
as it is from the echo canceller 21 has a phase of 0 degrees, the other audio signals become
audio signals of phases 90 degrees, 180 degrees, and 270 degrees, respectively. The audio
signals of different phases input to the D / A converter 23 are converted into analog audio
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signals, amplified by a plurality of sound emission AMPs 24, and emitted by the speakers SP1 to
SP4.
[0033]
FIG. 6 is a diagram showing an example in the case where sound is emitted by the speakers SP1
to SP4. In the same figure (A), the region 100A shows a region of θ = 45 ° between the speaker
SP1 and the speaker SP2, the region 100B shows a region of θ = 135 ° between the speaker
SP2 and the speaker SP3 and a region 100C indicates a region of θ = 225 ° between the
speaker SP3 and the speaker SP4, and a region 100D indicates a region of θ = 315 ° between
the speaker SP4 and the speaker SP1. Further, in FIG. 7B, an area 100E indicates an area at a
position immediately above the center position of the housing 11 (microphones 10A to 10P)
viewed from the top.
[0034]
The audio signal of phase 0 degree is input to the speaker SP1, the audio signal of phase 90
degree is input to the speaker SP2, the audio signal of phase 180 degree is input to the speaker
SP3, and the audio signal is input to the speaker SP4. , An audio signal with a phase of 270
degrees is input.
[0035]
In the area 100A, the sound emitted from the speaker SP1 and the sound emitted from the
speaker SP2 come.
Since the sound emitted from the speaker SP1 and the sound emitted from the speaker SP2 are
90 degrees out of phase at the speaker sound emission point, only the low band is not intensified
at the position of the area 100A, and it is clear I can hear it. Similarly, also in the area 100B, the
sound emitted from the speaker SP2 and the sound emitted from the speaker SP3 are 90 ° out
of phase at the speaker emission point, so that only the low band is not strengthened. You can
listen clearly. Similarly, in the area 100C, the sound emitted from the speaker SP3 and the sound
emitted from the speaker SP4 are 90 ° out of phase at the speaker sound emission point, so
only the low band is not strengthened. In the region 100D, the sound emitted from the speaker
SP4 and the sound emitted from the speaker SP1 are 90 degrees out of phase at the speaker
sound emission point, so the low frequency range can be obtained. It is not only intensified, but
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can be heard clearly.
[0036]
In the area 100E, the sound emitted from the speaker SP1, the sound emitted from the speaker
SP2, the sound emitted from the speaker SP3, and the sound emitted from the speaker SP4 come.
The sound emitted from each speaker is not intensified because the phases are shifted by 90
degrees at the speaker sound emission point. Further, since the sound emitted from the speaker
SP1 and the sound emitted from the speaker SP3 are 180 degrees out of phase with each other,
they cancel each other out and the volume decreases. Similarly, since the sound emitted from the
speaker SP2 and the sound emitted from the speaker SP4 are 180 degrees out of phase with
each other, they cancel each other out and the volume decreases.
[0037]
In the audio conference apparatus 1 according to the present embodiment, as described above,
although the sound that wraps around from the speaker to the microphone is structurally
extremely small, the phase of the sound emitted from each speaker is shifted by 90 degrees. The
S / N ratio is improved.
[0038]
Further, on the front of each speaker (for example, the front of the speaker SP1), the voices
coming from both sides (for example, the speakers SP2 and SP4) cancel each other, and only the
voice coming from the front can be heard clearly.
[0039]
Furthermore, at the position between the speakers (for example, between the speaker SP1 and
the speaker SP2), the phase of the sound coming from both speakers is 90 degrees out of phase,
so only the low band is not strengthened, and the volume change for each frequency band Can be
clearly heard.
[0040]
It is a figure which shows the external appearance of a voice conference apparatus.
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It is a block diagram which shows the structure of a voice conference apparatus.
FIG. 6 is a block diagram showing a detailed configuration of a microphone signal processing
circuit 27.
It is a block diagram which shows the detailed structure of an echo canceller. FIG. 2 is a block
diagram showing a detailed configuration of a speaker signal processing circuit 22. It is a figure
which shows the example when sound is emitted by speaker SP1-SP4.
Explanation of sign
[0041]
10A to 10P-Microphone 11-Case SP1 to SP4-Speaker
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