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DESCRIPTION JP2007300552

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DESCRIPTION JP2007300552
The present invention provides an audio signal transmitting / receiving apparatus capable of
transmitting / receiving an audio signal collected by a microphone and transmitting / receiving
an audio signal such as music with high sound quality. SOLUTION: A voice signal (speech voice
signal) collected by a microphone array 54 is converted to fs = 16 kHz to remove a feedback
component of the voice signal emitted from the speaker array 53, and passes through an echo
cancellation unit 70. Let On the other hand, the audio signal (musical tone signal) input from the
audio input terminal 62A is output without performing the echo cancellation processing with fs =
32 kHz. On the other hand, the speech voice signal and the musical tone signal received from the
other party are input to the echo cancellation unit 56. The sampling frequency of the musical
tone signal is down converted to 16 kHz and input. [Selected figure] Figure 3
Audio signal transmitter and receiver
[0001]
The present invention relates to an audio signal transmitting / receiving apparatus that transmits
/ receives an audio signal to / from a partner apparatus, and in particular, transmits / receives in
parallel a microphone collected signal picked up by a microphone and a line input signal inputted
from an audio input terminal. Audio signal transmitting / receiving apparatus.
[0002]
Conventionally, it has been proposed to transmit and receive voice signals between remote
locations via a network.
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By transmitting and receiving voice signals between remote locations, it is possible to make a
voice call such as a telephone call or a teleconference by voice. For example, Patent Document 1
proposes an apparatus for performing a remote audio conference.
[0003]
The device of Patent Document 1 emits an audio signal input through a network from a speaker
disposed on the top surface, and an opposite device through a network of an audio signal
collected by a microphone disposed on the side. And an echo canceller to remove the component
of the audio signal that is transmitted from the speaker to the microphone. JP-A-8-298696
[0004]
By the way, in transmission and reception of an audio signal between remote locations, there are
cases where it is desired to transmit and receive an audio signal such as music with high sound
quality. For example, when an audio signal such as music is used as the material of the remote
conference, or when it is desired to play BGM while talking with the other party.
[0005]
In such a case, in the above-described conventional apparatus, since an audio signal such as
music is also input through the microphone, the sound quality is deteriorated due to the
influence of the indoor acoustic characteristics, and the optimization is made for the transmission
of conversational speech. When digitized at the specified sampling frequency, a wide audio signal
of a frequency band such as music is degraded. In addition, although an echo cancellation
process is performed on an audio signal collected from a microphone to remove a wraparound
sound (feedback sound) from a speaker, the audio signal is also degraded by this echo
cancellation process.
[0006]
Due to the above reasons, in the conventional device, even if an audio signal such as music is
transmitted, it can not be transmitted with high sound quality.
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[0007]
SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present
invention to provide an audio signal transmitting / receiving apparatus capable of transmitting /
receiving an audio signal collected by a microphone and transmitting / receiving an audio signal
such as music with high sound quality.
[0008]
According to the first aspect of the present invention, a communication control unit for
transmitting an audio signal to a partner apparatus and receiving an audio signal from the
partner apparatus, and releasing a received audio signal, which is an audio signal received from
the partner apparatus, from a speaker A sound pickup unit, a microphone sound pickup unit that
picks up a microphone sound pickup signal, which is a first sound signal to be transmitted to the
partner apparatus, using a microphone, and a second sound signal to be transmitted to the
partner apparatus A signal input unit for inputting a line input signal via an audio input terminal;
a first conversion unit for converting the microphone pickup signal into a digital signal at a first
sampling frequency; and the speaker from the microphone pickup signal And an echo
cancellation unit for removing a feedback component of the received voice signal that has passed
through the microphone; and a second sampling that differs from the first sampling frequency
for the line input signal. Wherein the second conversion unit for converting into a digital signal
by the wave number, further comprising: a.
[0009]
In the present invention, the microphone sound pickup signal is, for example, a speech signal
uttered by the user of the device.
The line input signal is an audio signal used as a material of a conference, a musical tone signal
used as BGM, or the like.
Therefore, in the case of digitizing the microphone sound collection signal, it is sufficient to cover
the frequency band of conversational speech, for example, a sampling frequency of about 16 kHz
is sufficient.
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On the other hand, when digitizing a line input signal, for example, a high sampling frequency of
32 kHz or more is desirable in order to digitize music or the like having a wide frequency band.
Therefore, in the device according to the present invention, the sampling frequency of the line
input signal input from the audio input terminal is set higher than the sampling frequency of the
microphone collected signal which is an audio signal collected by the microphone.
[0010]
Then, since only the microphone sound collection signal includes the feedback signal component
of the emitted sound (received sound signal), the echo cancellation unit cancels the echo
(feedback signal component). That is, echo cancellation processing need not be performed on the
line input signal. This cancels the echo to the partner apparatus and does not degrade the sound
quality of the line input signal.
[0011]
In the invention of claim 2, the communication control unit transmits a first received voice signal
digitized at the first sampling frequency and a second received voice signal digitized at the
second sampling frequency from the partner apparatus. Receiving the echo cancellation unit is
an adaptive echo canceller operating at the first sampling frequency, and further converting the
second reception voice signal into a digital signal of the first sampling frequency to convert the
echo cancellation unit And a sampling frequency converter for supplying
[0012]
In the present invention, two types of audio signals are received from the opposite device.
That is, the first reception voice signal (for example, a speech voice signal in the partner
apparatus) of a normal sampling frequency and the second reception voice signal (for example,
line input signal in the partner apparatus) of a high sampling frequency are received. However,
since the echo cancellation unit operates at the first sampling frequency which is a normal
sampling frequency, the echo cancellation unit down-converts the sampling frequency of the
second received audio signal and inputs it to the echo cancellation unit. As a result, while
transmitting a signal of a high sampling frequency, echo can be canceled by a simple and
inexpensive echo cancellation unit with a low sampling frequency.
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[0013]
In the invention of claim 3, the communication control unit receives a reception voice signal
digitized at the second sampling frequency from the partner apparatus, and the echo cancellation
unit operates at the first sampling frequency. An adaptive echo canceller, further comprising: a
receiving-side sampling frequency converter that converts the received voice signal into a digital
signal of the first sampling frequency and supplies the digital signal to the echo cancellation unit;
and a microphone processed by the echo cancellation unit. And a transmission-side sampling
frequency converter for converting the collected sound signal into the second sampling
frequency.
[0014]
In the present invention, the microphone pickup signal is converted into a second sampling
frequency which is the same sampling frequency as the line input signal, and is input to the
communication control unit.
Thus, the communication control unit can process the microphone sound collection signal and
the line input signal as signals of the same sampling frequency, and the configuration can be
simplified. Also, in the case of the other device having the same configuration, the audio signals
of all the channels are transmitted as digital signals of the second sampling frequency. However,
since the echo cancellation unit operates at the first sampling frequency, it converts the sampling
frequency of the received voice signal into the first sampling frequency and inputs it to the echo
cancellation unit. As a result, while transmitting a signal of a high sampling frequency, echo can
be canceled by a simple and inexpensive echo cancellation unit with a low sampling frequency.
[0015]
According to the present invention, the user's conversational voice and the like are collected by
the microphone, and an audio source such as music is input as a line input signal from the audio
input terminal or the like, and the line input signal is higher than the microphone sound pickup
signal. By digitizing and transmitting at the second sampling frequency which is the sampling
frequency, the line input signal can be made high in sampling frequency and transmitted with
high sound quality by not being subjected to the echo cancellation processing. Can.
[0016]
Further, according to the present invention, when the first received voice signal digitized at the
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first sampling frequency and the second received voice signal digitized at the second sampling
frequency are received from the other device, By down converting the sampling frequency of the
second received audio signal to the first sampling frequency, the echo cancellation unit can be
simplified.
[0017]
An audio signal transmitting and receiving apparatus according to an embodiment of the present
invention will be described with reference to the drawings.
The voice signal transmitting / receiving apparatus 1 is an apparatus connected to a network
such as the Internet or a LAN and used.
The audio signal transmitting / receiving apparatus 1 transmits / receives an audio signal to /
from another audio signal transmitting / receiving apparatus which is a partner apparatus via a
network. The user can use the voice signal transmission / reception function of the voice signal
transmission / reception device 1 to conduct a call, a voice conference, and the like.
[0018]
FIG. 1 is a perspective view showing the appearance of the audio signal transmitting / receiving
apparatus 1. In the following description, in the direction axes of X-X and Y-Y shown in the
figure, the face in the Y direction of the audio signal transmitting / receiving device 1 is the front,
the face in the -Y direction is the back, the face in the X direction Is called the right side surface,
and the surface on the -X direction side is called the left side surface.
[0019]
The audio signal transmitting / receiving apparatus 1 has an external appearance in which a long
substantially rectangular parallelepiped apparatus main body 2 is supported at a predetermined
height from the installation surface by substantially square U-shaped legs 3 externally fitted on
both sides thereof. . The apparatus main body 2 constitutes a housing by the upper surface panel
20, the lower surface grille 21, and the left and right side panels 22.
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[0020]
The top panel 20 and the side panel 22 are made of a resin panel and cover an internal structure
including the speaker array 53 (see FIG. 3) and the microphone array 54 (see FIG. 3). The upper
surface panel 20 is a long member having a U-shaped cross section, and the side surface panel
22 is a flat plate-like member externally fitted to the upper surface panel 20 and the lower
surface grille 21 from the side. Further, the lower surface grille 21 is a wedge-shaped steel plate
having a substantially U-shaped cross section covering the lower surface of the apparatus main
body, and is opened in a punch mesh shape so as not to disturb the sound output from the inside
and the sound collection inside. .
[0021]
A speaker array 53 is provided on the bottom surface side inside the lower surface grille 21, and
a microphone array 54 is provided on the front side and the back side.
[0022]
The speaker array 53 is provided in a line downward on the lower surface of the apparatus body,
and the microphone arrays 54 are provided in a line toward the front and the back on the front
and the back which are both side surfaces of the speaker apparatus in the longitudinal direction. .
The speaker array 53 emits an audio signal received from the other device. Further, the
microphone array 54 picks up the speaker's speech signal. This speech signal corresponds to the
microphone pickup signal of the present invention. This conversational speech signal is
transmitted to the other device. The audio signal transmitting / receiving apparatus 1 emits a
sound by converting the audio signal received from the other party into a beam using the
speaker array 53. Further, the audio signal transmitting / receiving apparatus 1 picks up (beams)
only audio in a specific direction using the microphone array 54. The sound emission beam and
the sound collection beam will be described later.
[0023]
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An operation unit 4 is embedded at the right end of the upper surface of the upper surface panel
20. The operation unit 4 includes an LCD display for displaying a setting state and the like, and a
button switch group such as a ten key used for communication setting and the like.
[0024]
In the right side panel 22, a connector group 6 with an external device is embedded. The
connector group 6 includes a modular jack 61 for connecting to a LAN such as Ethernet
(registered trademark) or a network such as the Internet, an audio input terminal 62A and an
audio output terminal 62B for connecting to an audio device, and a power source. The power
supply terminal 63 is included.
[0025]
By inserting a plug of a LAN cable into the modular jack 61, the audio signal transmitting /
receiving apparatus 1 is connected to the network. By connecting a plurality of audio signal
transmitting / receiving apparatuses 1 to a network and setting them in a mutually
communicable state, it is possible to make a call or an audio conference.
[0026]
Also, an external audio device is connected to the audio input terminal 62A via an audio cable. A
musical tone signal which is a reproduced sound signal such as music reproduced by the audio
device is input to the apparatus without passing through the microphone array 54. That is, the
signal is input to the apparatus in a state different from the sound signal collected by the
microphone array 54 and completely separated from the noise collected by the microphone
array 54. The audio signal input from the audio input terminal 62A corresponds to the line input
signal of the present invention.
[0027]
Here, with reference to FIG. 2, a beam forming process (sound emitting beam) of an audio signal
using the speaker array 53 and a beam forming process (sound collecting beam) of a collected
signal using the microphone array 54 will be described. .
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[0028]
The figure (A) is a figure explaining a sound emission beam.
This sound emission beam sets a focal point (virtual sound source position) behind the speaker
array 53, and simulates a form in which an audio signal is diffused and propagated from the
virtual sound source position. The sound emission beam processing unit 52 (see FIG. 3) for
supplying an audio signal to each of the speaker units SP1 to SPN that constitute the speaker
array 53 has the delay time DS1 to the audio signal shown in FIG. The signal is delayed by DSN
and supplied to each of the speaker units SP1 to SPN. In this figure, each speaker emits sound
without delay time from the speaker closest to the virtual sound source position (focus point FS),
and emits sound after a delay time corresponding to the distance as it gets farther to the virtual
sound source position. Delay patterns are given. Due to this delay pattern, the sound outputted
from each of the speaker units SP1 to SPN forms a wave front similar to the sound emitted from
the virtual sound source in the figure and spreads, and it is possible to the meeting attendee who
is the user. The voice can be heard as if the other party's speaker is at the position of the virtual
sound source.
[0029]
As shown in FIG. 1, in the audio signal transmitting / receiving apparatus 1, since the speaker
array 53 is provided downward on the lower surface of the apparatus main body, the audio is
emitted downward from each speaker unit. For example, since sound is reflected by the top plate
of the conference table, sound emission beams are formed on the front side and the back side of
the audio signal transmitting and receiving device 1.
[0030]
The audio signal transmitting / receiving apparatus 1 of the embodiment sets virtual sound
source positions to three points of center (C) and left and right (L / R), assigns different audio
signals to each of them, and generates different sound sources for each virtual sound source
position. Output in parallel as there is.
In the voice signal assigned to each virtual sound source position, the center (C) is a
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conversational voice signal collected by the microphone (microphone array) of the other device,
and left and right (L / R) are input from the audio input terminal of the other device. It is a stereo
tone signal.
[0031]
The figure (B) is a figure explaining the sound collection beam formed with the sound signal
collected by the microphone array 54. FIG. The sound collection beam processing unit 55 (see
FIG. 3) delays the audio signals input to the microphone units MR1 to MRN of the microphone
array 54 by delay times DM1 to DMN respectively as shown in FIG. In this figure, the audio
signal collected by each microphone is input to the adding unit without any delay time, and the
sound collected by the microphone farthest to the collection area (focus FM) is closer to the
collection area as it gets closer A delay pattern which is input to the adder after being delayed
according to the distance is given. Due to this delay pattern, each audio signal becomes
equidistant in sound wave propagation from the pickup area (focus point FM), and each
synthesized audio signal emphasizes the audio signal of this pickup area in the same phase, and
The audio signal in the area is offset by phase shift. As described above, by delaying and
synthesizing the voices input to the plurality of microphones so as to be equidistant on sound
wave propagation from a certain sound collecting area, it is possible to pick up only the sound of
the sound collecting area.
[0032]
The voice signal transmitting / receiving apparatus 1 picks up a conversation voice signal which
is a voice produced by the speaker by focusing the sound collection beam on the position of the
speaker. This speech signal is digitized at a sampling frequency of 16 kHz and transmitted to the
other device. Also, a musical tone signal which is a 2-channel stereo audio signal input from the
audio input terminal 62A is digitized at a sampling frequency of 32 kHz and transmitted to the
other device. The transmission of the speech signal and the transmission of the musical tone
signal are simultaneously performed in parallel.
[0033]
On the other hand, the audio signal transmitting and receiving apparatus 1 also receives audio
signals of three systems in parallel from the opposite apparatus. The three speech signals are a
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speech speech signal with a sampling frequency of 16 kHz and a musical tone signal with two
channels of a sampling frequency of 32 kHz. As described above, the speech signal is emitted
with a wavefront that diffuses from the virtual sound source position set at the rear (upper side
in the apparatus of FIG. 1) of the speaker array 53. Also, the musical tone signal is emitted at the
wavefront so as to be diffused from the virtual sound source position set at the left and right rear
of the speaker array 53. As a result, for a user (speaker) who is sitting on the front side or the
back side of the device, the conversational voice can be heard from the front and the stereo
musical tone signals can be heard from the left and right front. You can listen to the audio signal.
[0034]
Here, the sound signal emitted from the speaker array 53 is reflected, refracted, and the like and
collected around the microphone array 54. If this wraparound signal (feedback signal) is sent to
the other device as it is, the other device will receive an echo, which is a signal component that is
delayed and returned by the own device. Therefore, the voice signal transmitting / receiving
apparatus removes the feedback signal component (the signal component emitted from the
speaker array 53 and getting into the microphone array 54) from the voice signal collected by
the microphone array 54 (FIG. 3). See). In this echo cancellation unit 70, three echo cancelers
71C, 71L, 71R are provided in series in accordance with the three systems of audio signals
received from the other device. However, since each echo canceller 71C, 71L, 71R operates at
the sampling frequency (16 kHz) of the audio signal picked up by the microphone array 54, the
reference signal input to the echo canceller 71L, 71R (2 received from the other device The tone
signal of the channel) is down-converted from 32 kHz to 16 kHz and then input. This eliminates
the need to have an echo canceller operating at a high speed of 32 kHz.
[0035]
On the other hand, however, echo cancellation processing is not performed on the tone signal
input from the audio input terminal 62A. This is because the audio signal emitted from the
speaker array 53 does not enter the audio input terminal 62A. As a result, the musical tone signal
has a high sampling frequency and high sound quality as compared with the conversational
speech signal, and the sound quality is not deteriorated due to the echo cancellation.
[0036]
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FIG. 3 is a block diagram of the audio signal transmitting / receiving apparatus 1. A modular jack
61 provided on the right side is connected to the network interface 50. The network interface 50
is a control unit that controls communication with a partner apparatus via a network. A signal
processing unit 51 is connected to the network interface 50. The signal processing unit 51 has a
function of decoding an audio signal from a packet received from the other device, packetizing
the audio signal input to the device, and transmitting the packetized signal to the network.
[0037]
As described above, the audio signal transmitting / receiving apparatus 1 receives audio signals
of three channels from the opposite apparatus. The three-channel audio signal is, as described
above, composed of a one-channel speech signal at a sampling frequency of 16 kHz and a twochannel musical tone signal at a sampling frequency of 32 kHz. The signal processing unit 51
decodes these audio signals, converts them into a bit stream, and inputs the bit stream to the
sound emission beam processing unit 52. The sound emission beam processing unit 52 controls
the timings of the sound signals of the three channels so as to be sound emission beams having
focal points at predetermined different positions.
[0038]
Note that, in addition to the sound emission beam control for forming the wavefront diffused
from the virtual focal position as described in FIG. 2, the sound emission beam processing unit
52 forms a spot beam converging on the focal point in front of the speaker array 53. Beam
control may be performed. In addition, without performing beam control, the plurality of speaker
units of the speaker array 53 may be divided into three groups, and each group may be made to
take charge of sound emission of the conversational speech signal and the musical tone signal of
two channels.
[0039]
In this way, the speech signal and the tone signal received from the partner apparatus are
emitted from the speaker array 53 and heard by the user 100. At the same time, it also wraps
around each microphone unit of the microphone array 54 and is collected as a feedback signal.
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[0040]
The sound collection beam processing unit 55 forms a sound collection beam focused on the
position of the user 100 by the delay process shown in FIG. 2B, and collects the speech of the
user 100. The collected sound signal is input to the echo cancellation unit 70 via the low pass
filter 56 as a speech signal.
[0041]
The low pass filter removes frequency components exceeding 8000 Hz from the tone signal so
that aliasing does not occur.
[0042]
The echo cancellation unit 70 is configured by connecting three echo cancelers 71C, 71L, 71R in
series in order to remove the signal component of each channel that has looped into the
microphone array 54, and the echo cancelers 71C, 71L, At 71R, the feedback signal components
of the speech signal from the other party, the tone signal of the L channel, and the tone signal of
the R channel are removed.
Each echo canceller is an adaptive echo canceller having an adaptive filter 72 and a post
processor 73. The adaptive filter 72 itself generates a filter coefficient that removes the reference
signal component from the residual signal based on the reference signal input from the signal
processing unit 51 and the residual signal input from the post processor 73. It is a thing. The
adaptive echo canceller is described in detail in, for example, Japanese Patent Application LaidOpen No. 2005-318518, which is a prior application of the present applicant.
[0043]
The audio signals emitted from the speaker array 53 are input from the signal processing unit 51
as reference signals to the echo cancellers 71C, 71C and 71R, but as described above, each echo
canceller has a sampling frequency of 16 kHz. The echo cancellers 71L and R for removing the
feedback signal component of the tone signal are processed by the low pass filters 57L and R and
the sampling rate converters 58L and R for the 32 kHz tone signal output from the signal
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processing unit 51. Signal is input. The low pass filters 57L and 57L remove frequency
components exceeding 8000 Hz from the tone signal so that aliasing does not occur. Then, the
sampling rate converters 58L and R down convert the signal of sampling frequency 32 kHz to
the signal of sampling frequency 16 kHz.
[0044]
The speech signal from which the echo component has been removed by the echo cancellation
unit 70 is input to the signal processing unit 51.
[0045]
On the other hand, an external audio device 30 is connected to the audio input terminal 62A.
The two-channel stereo audio signal reproduced by the audio device 30 is input from the audio
input terminal 62A as a musical tone signal. The tone signal is converted into a digital signal by
the A / D converter 60. The sampling frequency at the time of this A / D conversion is 32 kHz.
This musical tone signal is also input to the signal processing unit 51 in the same manner as the
conversational speech signal.
[0046]
The signal processing unit 51 edits these input signals into packets corresponding to the
sampling frequency, and sends them to the other device via the network interface 50 and sends
them to the network.
[0047]
Although the sampling frequency of the speech signal is 16 kHz and the sampling frequency of
the musical tone signal is 32 kHz in the above embodiment, the sampling frequency is not limited
to this.
It is sufficient if the sampling frequency of the musical tone signal is higher than the sampling
frequency of the speech signal and high sound quality.
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[0048]
An audio signal transmitting and receiving apparatus according to another embodiment of the
present invention will be described with reference to FIGS. 4 and 5.
[0049]
The audio signal transmitting and receiving apparatus shown in FIG. 4 is an example of a
configuration in which a conversational audio signal digitized at a sampling frequency of 16 kHz
is upconverted to a sampling frequency of 32 kHz and then input to the signal processing unit
51.
By doing this, the signal processing unit 51 can process the musical tone signals and the
conversational speech signals of two channels as signals of the same sampling frequency (32
KHz) by the same CODEC.
[0050]
In the block diagram of FIG. 4, the parts having the same configuration as the block diagram
shown in FIG. The echo cancellation unit 70 includes three echo cancellers 71C, 71L and 71R as
in the embodiment of FIG. 3, and operates at a sampling frequency of 16 kHz. As described with
reference to FIG. 3, the echo canceller 71C removes the feedback component of the speech signal
received from the other party. The echo canceller 71L removes the feedback component of the
left channel of the musical tone signal received from the other device. The echo canceller 71R
removes the feedback component of the right channel of the musical tone signal received from
the other device. The speech sound signal from which the feedback components of the received
three-channel sound signal have been removed is input to the sampling rate converter 74. The
sampling rate converter 74 up-converts this speech signal into a sampling frequency of 32 kHz
and inputs it to the signal processing unit 51.
[0051]
The signal processing unit 51 packetizes the conversational speech signal and the two-channel
musical tone signal input from the A / D converter 60 as the same sampling frequency 32 kHz
and inputs the packetized signal to the network interface 50.
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[0052]
On the other hand, the network interface 50 receives audio signals of three channels from the
other device, and the audio signals of the three channels are also the same sampling frequency of
32 kHz.
The signal processing unit 51 decodes this signal and outputs it as a 32 kHz stream signal, but as
described above, each of the echo cancelers 71C, 71L, 71R of the echo cancellation unit 70
operates at a sampling frequency of 16 kHz respectively Therefore, in addition to the low pass
filters 57L and 57R and the sampling rate converters 58L and R shown in FIG. 3, the C channel
low pass filter 57C and the sampling rate converter 58C are provided. The low pass filters 57C, L,
and R remove frequency components exceeding 8000 Hz from the audio signal having a
sampling frequency of 32 kHz so that no aliasing occurs. Then, the sampling rate converters 58C,
L, and R down convert the audio signal with the sampling frequency of 32 kHz into a signal with
the sampling frequency of 16 kHz.
[0053]
Next, a third embodiment will be described with reference to the block diagram of FIG. The audio
signal transmitting / receiving apparatus of this embodiment mixes the audio signals of three
channels received from the other party into one channel of audio signal and then outputs from
the speaker array 53 to the microphone array 54 from the speaker array 53. The feedback path
of is one, and the echo canceller provided in the echo cancellation unit 70 is one system.
[0054]
In the block diagram of FIG. 5, the parts having the same configuration as the block diagram
shown in FIG.
[0055]
The audio signals of three channels (speech audio signals and musical tone signals of two
channels) received from the partner apparatus are converted into stream signals by the signal
processing unit 51 and output to the mixer 75.
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The mixer 75 adds and synthesizes the audio signals of these three channels and converts it into
an audio signal of one channel. In this example, the audio signals of all three channels are 32
kHz. However, when the sampling frequencies of the respective channels are different, the
sampling frequencies are converted to match and then synthesized.
[0056]
The audio signal converted into one channel by the mixer 75 is input to the sound emission beam
processing unit 52 and the low pass filter 57. The sound emission beam processing unit 52
amplifies and delays the sound signal of one channel to emit a beam, and inputs the sound signal
to the speaker array 53.
[0057]
The echo cancellation unit 70 that removes the feedback component from the speaker array 53
to the microphone array 54 from the audio signal collected by the microphone array 54 includes
one echo canceller 71 corresponding to the audio signal of one channel. . Since the echo
canceller 71 operates at a sampling frequency of 16 kHz, the audio signal output from the mixer
75 is processed by the low pass filter 57 and the sampling rate converter 58 and then input to
the echo canceller 71. . The low pass filter 57 removes frequency components exceeding 8000
Hz from the mixed audio signal so that no aliasing occurs. Then, the sampling rate converter 58
down-converts the audio signal of sampling frequency 32 kHz into a signal of sampling
frequency 16 kHz.
[0058]
As described above, according to this configuration, since audio signals of three channels are
mixed with an audio signal of one channel and emitted, only one echo canceller is required.
[0059]
In each of the above embodiments, the number of channels of the tone signal is not limited to
two.
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There may be more channels or monaural.
[0060]
Further, in the above embodiment, the sound emitting unit is configured by the speaker array 53,
and the sound collecting unit is configured by the microphone array 54, but this configuration is
not essential. That is, instead of the speaker array 53, audio signals of one or more channels
received from the other device may be output from separate speakers, or may be output from a
single speaker system after mixing. Good. Also, instead of the microphone array 54, a single
microphone unit may be used to pick up the speaker's speech.
[0061]
In addition, when the operating frequency of the echo cancellation unit 70 is different from the
digitized sampling frequency of the audio signal collected by the microphone array 54 and the
operating frequency of the signal processing unit 51, the input side and the output of the echo
cancellation unit 70 A sampling rate converter may be inserted on the side.
[0062]
The external appearance perspective view of the audio signal transmitting and receiving
apparatus according to the embodiment of the present invention. Same as the sound emitting
beam and the sound collecting beam formed by the audio signal transmitting and receiving
apparatus. Block diagram of the processing unit of the audio signal transmitting / receiving
apparatus of the third embodiment The block diagram of the processing unit of the audio signal
transmitting / receiving apparatus of the third embodiment of the present invention
Explanation of sign
[0063]
DESCRIPTION OF SYMBOLS 1 ... Audio signal transmission / reception apparatus 61 ... Modular
jack 62A ... Audio input terminal 53 ... Speaker array 54 ... Microphone array 57 (57C, 57L, 57R)
... Sampling rate converter 70 ... Echo cancellation part 71C, 71L, 71R ... Echo canceler
15-04-2019
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