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DESCRIPTION JPH11284550

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DESCRIPTION JPH11284550
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
voice input / output device, and more particularly, an echo casera for removing an acoustic echo
signal which is output from a speaker and which is transmitted to a microphone, and removed by
the echo canceler. The present invention relates to a voice input / output device provided with an
echo suppressor for suppressing a residual signal which has not been completed.
[0002]
2. Description of the Related Art In voice communication systems using speakers and
microphones such as speakerphones and videophones, for example, techniques relating to echo
cancellers used so far for satellite communication etc. have recently been applied relatively
cheaply. It has come. Further, with the spread of mobile phones, the demand for devices
equipped with the above-mentioned echo canceller is also increasing. In particular, in the case of
a mobile phone or the like which is strongly required to be miniaturized, the distance between
the speaker and the microphone is short, and there is also a high possibility that an acoustic echo
signal which has traveled from the speaker to the microphone may adversely affect the call state.
Here, an example of a conventional voice input / output device for removing the influence of an
acoustic echo signal from input voice is shown in FIG. The voice input / output device includes a
microphone 400, a speaker 401, an acoustic echo canceller 402, and a non-linear processor 403.
In the above audio input / output device, an echo signal that has passed from the microphone
400 to the speaker 401 is suppressed by the acoustic echo canceller 402 that is configured by
an adaptive filter or the like. However, when the above-mentioned adaptive filter is not
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sufficiently converged, some residual signal is generated and transmitted to the far-end talker
side as it is. In the voice input / output apparatus, in order to prevent the residual signal not
removed by the acoustic echo canceller 402 from being transmitted to the far-end speaker or the
speech recognition apparatus, the non-linear processor (echo suppressor) 403 suppresses the
residual signal. It is provided at the rear stage of the acoustic echo canceller 402. FIG. 5 shows an
example of the characteristics of the non-linear processor. This is called a center clipper method.
In the center clipper method, the output is attenuated to 0 only when the residual signal of the
acoustic echo canceller 402 is within the range of threshold values ThL to ThH, and in the other
cases, the signal is allowed to pass. This operation prevents transmission of the residual signal to
the far-end speaker.
[0003]
When the residual signal is suppressed using a non-linear processor as described above, not only
the residual signal but also signals necessary for natural conversation such as background noise
are removed, Non-linear processor brings about rapid change of background sound, lack of
speech, etc., during frequent reception / transmission switching during double talk, and
switching from transmission / reception to transmission / reception after silence. There was a
problem of making you feel uncomfortable. In order to solve the problems in the prior art as
described above, the present invention improves the voice input / output device and
simultaneously switches the amount of attenuation of the residual signal based on the acoustic
echo signal and the size of the transmission voice. It is an object of the present invention to
provide a voice input / output device capable of making a natural call with no sound interruption
even in a two-way call state and with little influence of echo.
[0004]
In order to achieve the above object, the invention according to claim 1 generates a pseudo echo
signal with reference to a microphone, a speaker, and a speaker output signal output from the
speaker. An acoustic echo canceler for subtracting the pseudo echo signal from an acoustic echo
signal in which the speaker output signal is looped into the microphone; and an echo suppressor
for suppressing a residual signal of the acoustic echo signal and the pseudo echo signal. The
voice input / output device comprises: residual signal level measuring means for measuring the
level of the residual signal; and speaker output signal level measuring means for measuring the
level of the speaker output signal, the echo suppressor A transmit attenuator for attenuating a
transmit signal input from the microphone and transmitted to the far end speaker, and The
transmission signal attenuation based on the level of the residual signal measured by the residual
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signal level measuring means and the speaker output signal level measuring means and the level
of the speaker output signal. And an attenuator controller for controlling the amount of
attenuation of the receiver and the receiver attenuator, respectively. The invention according to
claim 2 is the voice input / output device according to claim 1, wherein the attenuator controller
controls the transmission signal and the reception signal together with the level of the residual
signal and the level of the speaker output signal. The attenuation amount of the transmission
attenuator and the reception attenuator is controlled based on the magnitude relationship of the
signals, the transmission signal is smaller than the reception signal in the reception state, and the
level of the speaker output signal is When the level of the residual signal is greater than the
predetermined speaker output signal threshold and the level of the residual signal is smaller than
the predetermined residual signal threshold, the attenuation controller attenuates the
transmission attenuator. Is set to the first attenuation amount, and in the case of the reception
state otherwise, the attenuation amount of the transmission attenuator is set to the second
attenuation amount smaller than the first attenuation amount, and It becomes by suppressing the
difference signal The door and the gist thereof. The invention according to claim 3 is
characterized in that, in the voice input / output device according to claim 2, in the transmission
state in which the transmission signal is larger than the reception signal, the attenuation
controller controls the reception attenuator. The gist is that the amount of attenuation is set to
the second amount of attenuation and the speaker output signal is suppressed. The invention
according to claim 4 is the voice input / output device according to claim 2 or 3, wherein in the
intermediate state where the transmission signal and the reception signal are at the same level,
the transmission by the attenuator controller is performed. The gist is that the attenuations of the
speech attenuator and the reception attenuator are set to half the value of the second
attenuation.
[0005]
In the voice input / output device according to the first aspect of the invention, transmission is
performed by the attenuator controller based on the level of the speaker output signal that is the
source of the acoustic echo signal and the level of the residual signal not removed by the acoustic
echo canceller. Since the attenuation amounts of the speech attenuator and the reception
attenuator are set, it is possible to provide the user with a natural speech environment in which
echo is less affected. Furthermore, according to the voice input / output device of the second
aspect, in the receiving state, the level of the speaker output signal is larger than the
predetermined speaker output signal threshold, and the level of the residual signal is If it is
smaller than the predetermined residual signal threshold, in other words, there is received
speech but there is no transmitted speech, and if there is no need to transmit a signal to the farend talker side, attenuation of the transmission attenuator The amount is set to, for example,
about -14 dB, and the residual signal is sufficiently suppressed. In addition, in the case of the
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above-mentioned reception state, in the other cases, the attenuation amount of the abovementioned transmission attenuation is set to, for example, about -6 dB. For example, even when
double talk or echo canceler has not converged, The residual signal is suppressed while
maintaining. Furthermore, according to the voice input / output device of the third aspect, in the
transmission state, the attenuation controller of the reception attenuator is set to, for example,
about -6 dB by the attenuator controller, and excessive volume emission from the speaker Can be
prevented. Furthermore, according to the voice input / output device of the fourth aspect, in the
intermediate state, the attenuation amount of the transmission attenuator and the reception
attenuator is set to, for example, -3 dB by the attenuator controller, and the transmission voice
and the reception Background noise is eliminated when there is no voice, preventing an
unnatural call condition.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to the accompanying drawings for understanding of the present
invention. Note that this embodiment is a specific example of the present invention, and is not of
the nature to limit the technical scope of the present invention. First, FIG. 1 shows a schematic
configuration of a voice input / output device according to the present embodiment. The voice
input / output device according to one embodiment of the present invention is used by being
connected to, for example, a mobile telephone etc., and the microphone output signal S output
from the microphone M, the speaker S, and the speaker S is An acoustic echo canceller 10 for
generating a pseudo echo signal 104 by reference and subtracting the pseudo echo signal 104
from an acoustic echo signal generated by the speaker output signal going into the microphone
M; and the acoustic echo signal and the pseudo echo signal 104 And the echo suppressor 20 for
suppressing the residual signal 105, as in the prior art. The speech input / output device differs
from the prior art in that the residual level monitor 108 (residual signal level measuring means)
for measuring the level of the residual signal 105 and the level of the speaker output signal 50
are measured. A speech signal attenuator 212 comprising a speaker signal level monitor 106
(speaker output signal level measuring means) for attenuating a speech signal input from the
microphone M and transmitted to the far end speaker by the echo suppressor 20. A receiver
attenuator 213 for attenuating a receiver signal received at the near end speaker side, the level
of the residual signal 105 measured by the residual level monitor 108 and the speaker signal
level monitor 106, and the speaker output Attenuator controller 21 for controlling the
attenuation amount of the transmission attenuator 212 and the reception attenuator 213 based
on the level of the signal 50 It is that it includes the door.
[0007]
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In addition, the attenuator controller 211 controls the transmission attenuator 212 and the
reception attenuator 213 based on the magnitude relationship between the transmission signal
and the reception signal, as well as the level of the residual signal 105 and the level of the
speaker output signal 50. The amount of attenuation Gtx and Grx of the speaker is controlled,
and the transmission signal is in a reception state smaller than the reception signal, and the level
of the speaker output signal 50 measured by the speaker output signal level monitor 106 is
predetermined. The attenuator controller 211 when the level of the residual signal 105
measured by the residual level monitor 108 is smaller than a predetermined speaker signal
threshold value. Sets the attenuation amount Gtx of the transmission attenuation unit 212 to, for
example, -14 dB (first attenuation amount), and other fields in the reception state. The, by the
attenuator controller 211 sets the attenuation amount Gtx of the transmitting attenuator 212, for
example, -6 dB (second attenuation), an audio output device for suppressing the residual signal
105.
[0008]
Next, details of the voice input / output device will be described.
In the voice input / output device, the reception signal 40 from the far-end speaker received by
the near-end speaker is input to the echo suppressor 20. In the echo suppressor 20, the
instantaneous level of the reception signal 40 is averaged by the level detector 202 for a fixed
time to calculate the reception signal level b2 (204). On the other hand, a transmission signal
(microphone input signal) 30 input from the microphone M and transmitted to the far end
speaker side is input to the echo suppressor 20 through the acoustic echo canceller 10. In the
echo suppressor 20, the instantaneous level of the transmission signal 30 is averaged for a fixed
time by the level detector 201, and the transmission signal level b0 (203) is calculated. Then, the
transmission signal level b0 (203) and the reception signal level b2 (204) calculated by the two
level detectors 201 and 202 are output to the transmission / reception determination unit 205,
respectively. In the transmission / reception determination unit 205, the transmission state
(mainly a state in which the reception signal is attenuated) and the reception state (mainly
transmission) according to the magnitudes of the transmission signal level b0 (203) and the
reception signal level b2 (204). A state in which the speech signal is attenuated is determined,
and the corresponding determination signal L1 (206) is output to the attenuator controller 211.
In the transmission state, the determination signal L1 is 0, and in the reception state, the
determination signal L1 is 1. Further, based on the transmitted signal level b0 (203) from the
level detector 201, the transmitted voiced detector 207 determines whether the transmitted
signal is in the voiced state or in the unvoiced state, and the corresponding determination is
made. The signal Nt (208) is output to the attenuator controller 211. When the transmission
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signal is in the voiced state, the determination signal Nt is 1, and in the unvoiced state, the
determination signal Nt is 0. Similarly, based on the received signal level b2 (204) from the level
detector 202, the received voiced detector 209 determines whether the received signal 40 is
voiced or unvoiced, and the discrimination signal corresponding thereto is determined. N r (210)
is output to attenuator controller 211. When the reception signal is in the voiced state, the
determination signal Nr is 1, and in the unvoiced state, the determination signal Nt is 0.
[0009]
Further, the acoustic echo canceller 10 generates a pseudo echo signal 104 by the adaptive filter
103 using the reception signal (speaker output signal) 50 attenuated by the reception attenuator
213 as a reference signal. Then, by subtracting the pseudo echo signal 104 from the
transmission signal 30 input from the microphone M, the acoustic echo signal that has entered
the speaker S from the microphone M is suppressed. An echo suppressor 20 suppresses the
disappearing residual signal of the acoustic echo canceller 10, that is, the residual signal 105 of
the acoustic echo signal and the pseudo echo signal 104. Also, the magnitude of the speaker
output signal 50 is measured by the speaker signal level monitor 106, and a speaker output
signal detection flag Tm (101) is generated. If the speaker output signal detection flag Tm is
larger than a predetermined speaker output signal threshold value, Tm = 1 is set, and if smaller,
Tm = 0. The residual signal 105 of the acoustic echo canceller 10 is measured by the residual
level monitor 108 to generate a residual detection flag Rm (102). If the residual detection flag
Rm is smaller than the threshold value, Rm = 1 is set, and if smaller, Rm = 0. In the voice input /
output device according to the present embodiment, based on the speaker output signal flag Tm
(101) and the residual detection flag determination signal Rm (102), in addition to the
determination signals L1, Nt and Nr, The attenuator controller 211 of the echo suppressor 211
controls the attenuation amount Gtx of the transmission attenuator 212 and the attenuation
amount Grx of the reception attenuator 213. An example of the attenuation amounts Gtx and Grx
of the transmission attenuator 212 and the reception attenuator 213 set by the attenuator
controller 211 based on the discrimination signals L1, Nt and NR and the flags Tm and Rm is
shown in FIG. An example of the operation is shown in FIG.
[0010]
Next, with reference to FIGS. 2 and 3, the detailed operation of the voice input / output device
will be described. The state A is a transmission state, and the transmission signal 30 is present. At
this time, the attenuation controller 211 sets the attenuation of the transmission attenuator 212
to 0 dB, and the attenuation of the reception attenuator 213 to -6 dB. As a result, the speaker
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volume of the incoming call is slightly reduced, but it is not at a level that would disturb the
conversation. The state B is a transmission state, but the transmission signal 30 is in a silent
state. At this time, the attenuation controller 211 sets the attenuation of the transmission
attenuator 212 to −3 dB and the attenuation of the reception attenuator 213 to −3 dB, and
both are in balance. In the transition from state A to state B, the change of each attenuator is
gradual. The state C is a receiving state, but the receiving sound 40 is a silent state. The settings
of the attenuators 212 and 213 at this time are the same as in the above-mentioned state B. The
intermediate state in the present invention corresponds to the above-mentioned state B or state
C. State D is a receiving state, but the speaker output signal 50 is smaller than a predetermined
speaker output signal threshold and the residual signal 105 is larger than a predetermined
residual signal threshold. This state D often occurs at the beginning of the reception, at the time
of double talk in which both transmission voice and reception voice are present. At this time, the
attenuation controller 211 sets the attenuation of the transmission attenuator 212 to -6 dB, and
the attenuation of the reception attenuator 213 to 0 dB. In this state D, since the speaker output
signal 50 is small, the echo signal contained in the residual signal 105 is minute. The state E is a
receiving state, in which the speaker output signal 50 is larger than the predetermined speaker
output signal threshold and the residual signal 105 is larger than the predetermined residual
signal threshold. This state E occurs, for example, when the operation of the echo canceller 10
starts. At this time, the attenuation controller 211 sets the attenuation of the transmission
attenuator 212 to -6 dB, and the attenuation of the reception attenuator 213 to 0 dB. State F is a
receiving state where the speaker output signal 50 is smaller than the predetermined speaker
output signal threshold and the residual signal 105 is smaller than the predetermined residual
signal threshold. This state F occurs when both the transmission voice and the reception voice
are small. At this time, the attenuation controller 211 sets the attenuation of the transmission
attenuator 212 to -6 dB, and the attenuation of the reception attenuator 213 to 0 dB. In this state
F, the residual signal 105 is hardly transmitted to the far end talker side.
The state G is a receiving state, and the speaker output signal 50 is larger than a predetermined
speaker output signal threshold, and the residual signal 105 is smaller than a predetermined
residual signal threshold. In this state G, there is no transmission voice and only reception voice
is present, and the adaptive filter 103 used in the echo canceller 10 converges to a
predetermined level, and the residual signal 105 of the echo canceller 10 becomes a
predetermined level. It is the case when it becomes small. At this time, the attenuation controller
211 sets the attenuation of the transmission attenuator 212 to -14 dB, the attenuation of the
reception attenuator 213 to 0 dB, and the residual signal 105 from the acoustic echo canceler 10
is sufficiently suppressed. . As described above, in the voice input / output device according to
the present embodiment, the attenuation amount of the transmission attenuator and the
reception attenuator is set based on the sizes of the speaker output signal and the residual signal
to suppress the echo signal. Thus, it is possible to provide a conversation environment in which
no sound is cut off and the influence of echo is small even in the simultaneous two-way call state.
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[0011]
In the above embodiment, the voice input / output device according to the present invention is
used for pre-processing of the telephone, but the present invention is not limited to this. Further,
the attenuation amounts of the transmission attenuator and the reception attenuator in each
state are not limited to the above example. Such a voice input / output device is also an example
of the voice input / output device in the present invention.
[0012]
As described above, in the voice input / output device according to claim 1, the level of the
speaker output signal which is the source of the acoustic echo signal and the level of the residual
signal not removed by the acoustic echo canceller Since the attenuation controller sets
attenuations of the transmission attenuator and the reception attenuator based on the
attenuation controller, it is possible to provide the user with a natural speech environment in
which echo is less affected. Furthermore, according to the voice input / output device of the
second aspect, in the receiving state, the level of the speaker output signal is larger than the
predetermined speaker output signal threshold, and the level of the residual signal is If it is
smaller than the predetermined residual signal threshold, in other words, there is received
speech but there is no transmitted speech, and if there is no need to transmit a signal to the far
end talker, attenuation of the transmission attenuator The amount is set to, for example, about 14 dB, and the residual signal is sufficiently suppressed. In addition, in the case of the abovementioned reception state, in the other cases, the attenuation amount of the above-mentioned
transmission attenuation is set to, for example, about -6 dB. For example, even when double talk
or echo canceler has not converged, The residual signal is suppressed while maintaining.
Furthermore, according to the voice input / output device of the third aspect, in the transmission
state, the attenuation controller of the reception attenuator is set to, for example, about -6 dB by
the attenuator controller, and excessive volume emission from the speaker Can be prevented.
Furthermore, according to the voice input / output device of the fourth aspect, in the
intermediate state, the attenuation amount of the transmission attenuator and the reception
attenuator is set to, for example, -3 dB by the attenuator controller, and the transmission voice
and the reception Background noise is eliminated when there is no voice, preventing an
unnatural call condition.
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