JP2004040161A - Hands-free mobile phone terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile phone terminal provided with an echo suppressing unit to reduce the amount of processing required for double-talk discrimination processing. <P>SOLUTION: The echo suppressing unit is provided with: first and second microphones 1, 2 for collecting transmission voice; first and second amplifiers 12, 13 corresponding to the first and second microphones respectively; and a loudspeaker 3 for outputting received voice, wherein an amplification factor of the first amplifier 1 is selected differently from an amplification factor of the second amplifier 2. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an echo suppression unit for a mobile phone that enables hands-free communication, a mobile phone terminal device equipped with such an echo suppression unit for a mobile phone, and an echo suppression method in a mobile phone.
[0002]
[Prior art]
2. Description of the Related Art In recent years, there has been proposed a mobile phone terminal device that enables a hands-free call by outputting a reception voice from a speaker of the mobile phone terminal device.
[0003]
However, since the mobile phone terminal device is small, there has been a problem that an echo signal level generated when the mobile phone terminal device goes around from the speaker to the microphone is large.
[0004]
In order to solve this problem, it is necessary that the mobile phone terminal device includes an echo canceller and a voice switch. For this reason, a mobile phone terminal device including an echo canceller and a voice switch using a pair of microphones and a speaker is required. Many have been devised.
[0005]
[Problems to be solved by the invention]
However, the echo canceller and the voice switch are provided when only the near-end speaker's voice exists, when the far-end speaker's voice and echo exist, and when the near-end speaker's voice, far-end speaker's voice and echo exist. There is a problem that a smooth call cannot be realized unless three call states in the case (double talk) are identified and control is performed according to each call state.
[0006]
In order to solve this problem, for example, Japanese Patent Application Laid-Open No. H11-215033 proposes a mobile phone terminal device that detects double talk from a power ratio of a transmission and reception signal.
[0007]
Further, Japanese Patent Application Laid-Open No. 7-303071 proposes a mobile phone terminal device that detects the voice pitch of a transmission / reception signal and compares the correlation between them to detect double talk.
[0008]
However, the method implemented in these portable terminal telephone devices has a drawback that the circuit scale is large because the processing is complicated.
[0009]
To solve this problem, an echo suppression method using two microphones has been proposed.
[0010]
For example, Japanese Patent Laying-Open No. 2000-324233 proposes a mobile phone terminal device that removes echoes by disposing two microphones at the same distance from a speaker and collecting echo signals in the same phase.
[0011]
However, according to this mobile phone terminal device, two microphones must be arranged at the same distance from the speaker and on the same surface, and thus there is a problem that the design of the mobile phone terminal device is significantly restricted. .
[0012]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems in the conventional mobile phone terminal device, and has as its object to provide an echo suppression unit for a mobile phone that reduces the processing amount required for the double talk determination process.
[0013]
[Means for Solving the Problems]
In order to achieve this object, first and second microphones for collecting transmission voice, first and second amplifiers respectively corresponding to the first and second microphones, and receiving voice are output. And a speaker, wherein the amplification factor of the first amplifier and the amplification factor of the second amplifier are different from each other. provide.
[0014]
In this mobile phone echo suppression unit, it is preferable that the distance from the first microphone to the speaker is set to be longer than the distance from the second microphone to the speaker.
[0015]
Further, the present invention provides a first microphone for collecting transmission voice, a second microphone for collecting transmission voice, a speaker for outputting reception voice, and amplifying an output signal of the first microphone. A first amplifier, a second amplifier that amplifies the output signal of the second microphone, a level detector that detects the level of the received signal, and emits a signal indicating the detected level, Based on an output signal from the second amplifier and a signal from the level detector, a call state of a mobile phone terminal device equipped with the present mobile phone echo suppression unit is detected, and a signal corresponding to the detected call state is detected. And a echo canceller that removes an echo component included in a transmission signal output from the first microphone in accordance with a signal from the double talk detector. Anne The amplification factor of the amplification factor of the second amplifier to provide a mobile phone echo suppression unit that is set to mutually different values.
[0016]
The echo suppression unit for a mobile phone amplifies a signal sent from an external decoder and transmits the signal to the echo canceller, and the echo canceller according to an amplification rate specified by the double talk detector. And a fourth amplifier for amplifying the transmission signal transmitted from the external encoder and transmitting the amplified transmission signal to the external encoder.
[0017]
In the above-described echo suppression unit for a mobile phone, it is preferable that the distance from the first microphone to the speaker is set to be longer than the distance from the second microphone to the speaker.
[0018]
This mobile phone echo suppression unit extracts a low-pass component in the output from the first microphone, and outputs a low-pass filter to the first amplifier, and a low-pass filter in the output from the second microphone. And a second low-pass filter for extracting the component and outputting the component to the first amplifier.
[0019]
The above-described echo suppression unit for a mobile phone according to the present invention can be mounted on a mobile phone terminal and used.
[0020]
Further, the present invention provides first and second microphones for collecting transmission voice, first and second amplifiers respectively corresponding to the first and second microphones, and a speaker for outputting reception voice. And a step of amplifying an output signal from the first microphone in the first amplifier, wherein the first amplifier in the second amplifier, Amplifying the output signal from the second microphone according to an amplification factor different from the amplification factor when amplifying the output signal from the first microphone in the amplifier; and Determining double talk based on an output signal.
[0021]
The above-described echo suppression method extracts the low-frequency component in the output from the first microphone, outputs the low-frequency component to the first amplifier, and extracts the low-frequency component in the output from the second microphone. And outputting to one amplifier.
[0022]
Further, the present invention is the echo suppressing method in the echo suppressing unit for a mobile phone as described above, wherein a step of calculating a first average signal power of a transmission signal output from the first amplifier; Calculating a second average signal power of the transmission signal output from the amplifier, and determining whether a difference between the first average signal power and the second average signal power is equal to or greater than a threshold value. And when the difference between the first average signal power and the second average signal power is smaller than the threshold, the value of the loss insertion counter of the double talk detector is set to a positive value. And the step of making the value of the loss insertion counter equal to or less than the threshold value, the step of updating the filter coefficient of the echo canceller, and the step of increasing the amplification factor of the fourth amplifier from its initial value. Set to a small value The method comprising, providing an echo suppression method comprising.
[0023]
Further, the present invention is the echo suppressing method in the echo suppressing unit for a mobile phone as described above, wherein a step of calculating a first average signal power of a transmission signal output from the first amplifier; Calculating a second average signal power of the transmission signal output from the amplifier, and determining whether a difference between the first average signal power and the second average signal power is equal to or greater than a threshold value. And, if the difference between the first average signal power and the second average signal power is greater than or equal to the threshold, determine whether the received signal level is greater than or equal to the threshold. And if the received signal level is greater than or equal to a threshold, add a positive value to the value of the loss insertion counter of the double talk detector, stop updating the filter coefficient of the echo canceller, Fourth amplifier increase Providing echo suppression method comprising the steps of: setting the rate to a value smaller than its initial value.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a block diagram of a mobile phone echo suppression unit according to the first embodiment of the present invention. The echo suppression unit for a mobile phone according to the present embodiment is included in a hands-free mobile phone terminal device (not shown).
[0025]
As shown in FIG. 1, the echo suppression unit for a mobile phone according to the present embodiment includes a first microphone 1, a second microphone 2, a speaker 3, and a first analog-digital (A / D) converter. (ADC) 4, a second A / D converter (ADC) 5, a digital-analog (D / A) converter (DAC) 6, a first noise suppressor (NS) 7, a second Noise suppressor (NS) 8, a first low-pass filter (LPF) 9, a second low-pass filter (LPF) 10, a level detector 11, a first amplifier 12, and a second amplifier 13. , A double talk detector 14, an echo canceller 15, a third amplifier 16, and a fourth amplifier 17.
[0026]
The first microphone 1 is connected to the first A / D converter 4, converts the collected sound and ambient noise into an electric signal, and sends the electric signal to the first A / D converter 4.
[0027]
The second microphone 2 is connected to the second A / D converter 5, converts the collected sound and ambient noise into electric signals, and sends the electric signals to the second A / D converter 5.
[0028]
The speaker 3 is connected to the D / A converter 6, and converts an electric signal sent from the D / A converter 6 into a sound and outputs the sound.
[0029]
The distance from the first microphone 1 to the speaker 3 is arranged to be longer than the distance from the second microphone 2 to the speaker 3.
[0030]
This is to make the level of the audio signal flowing from the speaker 3 to the first microphone 1 different from the level of the audio signal flowing from the speaker 3 to the second microphone 2.
[0031]
The first A / D converter 4 is connected to the first microphone 1 and the first noise suppressor 7, converts an analog signal sent from the first microphone 1 into a digital signal, and converts this digital signal into a digital signal. 1 to the noise suppressor 7.
[0032]
The second A / D converter 5 is connected to the second microphone 2 and the second noise suppressor 8, converts an analog signal sent from the second microphone 2 into a digital signal, and converts this digital signal to a second signal. 2 to the noise suppressor 7.
[0033]
The D / A converter 6 is connected to the speaker 3, the level detector 11, and the echo canceller 15, converts a digital signal sent from the echo canceller 15 into an analog signal, and sends the analog signal to the speaker 3.
[0034]
The first noise suppressor 7 is connected to the first A / D converter 4, the first low-pass filter 9, and the echo canceller 15, and converts the digital signal sent from the first A / D converter 4. The digital signal from which the noise component contained is removed is sent to the first low-pass filter 9 and the echo canceller 15.
[0035]
The second noise suppressor 8 is connected to the second A / D converter 5 and the second low-pass filter 10, and includes a noise component included in the digital signal sent from the second A / D converter 5. , And the digital signal after the removal is sent to the second low-pass filter 10.
[0036]
The first low-pass filter 9 is connected to the first noise suppressor 7 and the first amplifier 12, extracts a low-frequency component of the digital signal sent from the first noise suppressor 7, and extracts the low-frequency component. Send to the first amplifier 12.
[0037]
According to the experimental results of the inventor, when the distance from the near end speaker to the first microphone 1 and the second microphone 2 is far, the transmission frequency characteristics of the two microphones 1 and 2 in the low frequency region. Are approximately equal. For this reason, the first low-pass filter 9 is provided, and only the low-frequency component of the digital signal is used as a factor for the double talk determination.
[0038]
The second low-pass filter 10 is connected to the second noise suppressor 8 and the second amplifier 13, extracts a low-frequency component of the digital signal sent from the second noise suppressor 8, and extracts the low-frequency component. The signal is sent to the second amplifier 13.
[0039]
The reason for providing the second low-pass filter 10 is the same as the reason for providing the first low-pass filter 9 described above.
[0040]
The level detector 11 is connected to the double talk detector 14 and the echo canceller 15, calculates the received signal power transmitted from the echo canceller 15, and outputs received signal level information indicating the calculated received signal power to the double talk detector 14. Send to
[0041]
The first amplifier 12 is connected to the first low-pass filter 9 and the double-talk detector 14, amplifies the digital signal sent from the first low-pass filter 9, and sends the digital signal to the double-talk detector 14.
[0042]
The second amplifier 13 is connected to the second low-pass filter 10 and the double talk detector 14, amplifies the digital signal sent from the second low-pass filter 10, and sends the digital signal to the double talk detector 14.
[0043]
The amplification factors of the first amplifier 12 and the second amplifier 13 are such that an audio signal output from the speaker 3 is collected by the first microphone 1 and passes through the first noise suppressor 7 and the first low-pass filter 9. And the audio signal level output from the speaker 3 is collected by the second microphone 2 and passed through the second noise suppressor 8 and the second low-pass filter 10. It is set to be equal.
[0044]
The double talk detector 14 is connected to the level detector 11, the first amplifier 12, the second amplifier 13, the echo canceller 15, and the fourth amplifier 17, and receives the received signal level sent from the level detector 11. Based on the information, the digital signal sent from the first amplifier 12, and the digital signal sent from the second amplifier 13, a call state is detected, and the operation of the echo canceller 15 is performed according to the detected call state. The amplification factor of the fourth amplifier 17 is changed.
[0045]
The double talk detector 14 includes a loss insertion counter (not shown) for setting an amplification factor of a fourth amplifier 17 described later.
[0046]
The echo canceller 15 is connected to the D / A converter 6, the first noise suppressor 7, the level detector 11, the double talk detector 14, the third amplifier 16 and the fourth amplifier 17, and the third amplifier A pseudo echo signal is created based on the reception signal transmitted from the first noise suppressor 16, the echo component included in the transmission signal transmitted from the first noise suppressor 7 is removed, and the transmission signal after the removal is converted to a fourth signal. And an echo path is estimated based on the transmission signal sent to the fourth amplifier 17.
[0047]
The third amplifier 16 is connected to the echo canceller 15 and a decoder (not shown), amplifies a signal sent from the decoder (not shown), and sends the amplified signal to the echo canceller 15.
[0048]
The fourth amplifier 17 is connected to the double talk detector 14, the echo canceller 15, and an encoder (not shown). The amplified transmission signal is sent to an encoder (not shown).
[0049]
FIG. 2 is a flowchart showing the operation of the mobile phone echo suppression unit according to the present embodiment. Hereinafter, the operation of the mobile phone echo suppression unit according to the present embodiment will be described with reference to FIG.
[0050]
When the mobile phone terminal device equipped with the mobile phone echo suppression unit according to the present embodiment is in a talking state, the double talk detector 14 sets the value of the loss insertion counter n to 0, and the fourth amplifier 17 The amplification factor is initialized, that is, an amplification factor initial value A of the fourth amplifier 17 is set (step A1).
[0051]
The amplification factor initial value A of the fourth amplifier 17 is a constant that can be arbitrarily set by the maker of the mobile phone echo suppression unit according to the present embodiment.
[0052]
Next, the double talk detector 14 acquires the transmission signal for 160 samples from the first amplifier 12 (step A2).
[0053]
Next, a first average signal power P1 is calculated by calculating a root-mean-square of the transmission signal for 160 samples (step A3).
[0054]
Similarly, the double talk detector 14 obtains the transmission signal for 160 samples from the second amplifier 13 (step A4), and calculates the mean square of the transmission signal for 160 samples to obtain the second average signal. The power P2 is calculated (step A5).
[0055]
As described above, the average power of the transmission signal for 160 samples is calculated because the signal power due to the time difference generated when the sound generated from the same signal source is collected by the first microphone 1 and the second microphone 2 This is to reduce the difference.
[0056]
Next, the double talk detector 14 receives the received signal level L from the level detector 11 (Step A6).
[0057]
Next, the double talk detector 14 determines whether or not the absolute value of the difference between the first average signal power P1 and the second average signal power P2 is equal to or greater than a threshold value Pth (Step A7).
[0058]
If the collected signal is an echo component of a sound generated from the speaker 3, the absolute value of the difference between the first average signal power P1 and the second average signal power P2 is smaller than the threshold value Pth. (NO in Step A7), +1 is added to the value of the loss insertion counter n to suppress the echo component (Step A8).
[0059]
Next, it is confirmed whether or not the value of the loss insertion counter n is equal to or less than a threshold value nth (step A9).
[0060]
If the value of the loss insertion counter n is larger than the threshold value nth (NO in step A9), the value of the loss insertion counter n is set to nth (step A10).
[0061]
This is to prevent the amplification factor of the fourth amplifier 17 from becoming -∞.
[0062]
Next, the double talk detector 14 starts updating the filter coefficient of the echo canceller 15 (step A11).
[0063]
Further, the double talk detector 14 sets the amplification factor of the fourth amplifier 17 to (−6 × n + initial value A) [dB] (Step A12).
[0064]
Thereafter, the process returns to step A2, and the steps after step A2 are repeated.
[0065]
When the near-end speaker's voice is present, the sensitivity difference between the first microphone 1 and the second microphone 2 is small, and the gain of the first amplifier 13 is larger than the gain of the second amplifier 14. Then, the absolute value of the difference between the first average signal power P1 and the second average signal power P2 is equal to or larger than the threshold value Pth (YES in step A7).
[0066]
Therefore, in order to determine double talk, it is checked whether or not the received signal level L obtained from the level detector 11 is equal to or more than the threshold Lth (step A13).
[0067]
When there is no reception signal, the reception signal level L becomes less than the threshold value Lth (NO in step A13).
[0068]
For this reason, the double talk detector 14 determines that it is a single talk, and adds -1 to the value of the loss insertion counter n (step A14).
[0069]
Next, the double talk detector 14 checks whether or not the value of the loss insertion counter n is equal to or greater than 0 (Step A15).
[0070]
When the value of the loss insertion counter n is 0 or more (YES in step A15), the update of the filter coefficient of the echo canceller 15 is started (step A11), and the amplification factor of the fourth amplifier 17 is set to (−6 ×). n + initial value A) [dB] (Step A12), and the process returns to Step A2.
[0071]
When the value of the loss insertion counter n is less than 0 (NO in step A15), 0 is substituted for the value of the loss insertion counter n (step A16).
[0072]
Thereafter, updating of the filter coefficient of the echo canceller 15 is started (step A11), and the amplification factor of the fourth amplifier 17 is set to (−6 × n + initial value A) [dB] (step A12), and step A2 is performed. Return to
[0073]
In the case of double talk, the reception signal level L becomes equal to or higher than the threshold Lth in step A13 (YES in step A13).
[0074]
Therefore, in order to prevent howling, +1 is substituted for the value of the loss insertion counter n (step A17), updating of the filter coefficient of the echo canceller 15 is stopped (step A18), and the fourth amplifier 17 The amplification factor is set to (−6 × n + initial value A) [dB] (step A12), and the process returns to step A2.
[0075]
According to the echo suppressing unit for a mobile phone according to the present embodiment having the above operation, the following effects can be obtained.
[0076]
The first effect is that the processing amount required for the double talk determination processing can be reduced.
[0077]
This is because it is possible to determine whether the voice collected using the sensitivity difference between the two microphones 1 and 2 is an echo or a near-end speaker's voice without performing the frequency conversion process. It is.
[0078]
A second effect is that the accuracy of double talk determination can be improved.
[0079]
This is because it is possible to determine whether the voice collected using the sensitivity difference between the two microphones 1 and 2 is an echo or a near-end speaker voice.
[0080]
In the echo suppression unit for a mobile phone according to the present embodiment, various modifications are possible as follows.
[0081]
In the operation of step A2 in the flowchart of the mobile phone echo suppression unit according to the present embodiment shown in FIG. 2, the double talk detector 14 has obtained a signal of 160 samples from the first amplifier 12; The number of samples that the talk detector 14 should acquire from the first amplifier 12 is not limited to 160. It is possible to select any number of samples.
[0082]
Similarly, in the operation of step A4, the double talk detector 14 has obtained a signal of 160 samples from the second amplifier 13, but the double talk detector 14 has obtained the number of samples to be obtained from the second amplifier 13. Is not limited to 160. It is possible to select any number of samples.
[0083]
In the operation of step A12, the double talk detector 14 sets the gain of the fourth amplifier 17 to (−6 × n + initial value A) [dB]. The subtraction coefficient in this case is not limited to -6. Any negative coefficient value other than -6 can be selected.
[0084]
Further, in the operation of step A17, the set value of the loss insertion counter n is set to +1; however, the set value of the loss insertion counter n is not limited to +1. Any positive number other than +1 can be selected.
[0085]
FIG. 3 is a flowchart of the mobile phone echo suppression unit according to the second embodiment of the present invention.
[0086]
The mobile phone echo suppression unit according to the second embodiment has the same configuration as the mobile phone echo suppression unit according to the first embodiment shown in FIG. 1, but in terms of the operation described below. This is different from the echo suppression unit for mobile phones according to the first embodiment.
[0087]
In the mobile phone echo suppression unit according to the first embodiment, the amplification factor of the fourth amplifier 17 in the operation of step A12 is set to (−6 × n + initial value A) [dB]. In contrast, in the mobile phone echo suppression unit according to the present embodiment, the amplification factor of the fourth amplifier 17 in the operation of step A12 is set to (A−n ² ) [dB].
[0088]
This makes it possible to set the change amount of the amplification factor of the fourth amplifier 17 in a quadratic curve.
[0089]
In the mobile phone echo suppression unit according to the first embodiment, the set value of the loss insertion counter n in the operation of step A17 is +1. On the other hand, in the echo suppression unit for a mobile phone according to the present embodiment, the set value of the loss insertion counter n in the operation of Step A17 is set to 2.45.
[0090]
As a result, the amplification factor of the fourth amplifier 17 can be attenuated by 6 [dB] during double talk (n ² ≒ 6 in (A−n ² ) [dB] in step A12).
[0091]
Any value can be selected as the set value of the loss insertion counter n. Thus, the attenuation of the amplification factor of the fourth amplifier 17 can be adjusted according to the set value of the loss insertion counter n.
[0092]
【The invention's effect】
As described above, according to the present invention, it is determined whether the sound collected using the sensitivity difference between the two microphones is an echo or a near-end speaker's voice without performing the frequency conversion process. Can be determined.
[0093]
As a result, the processing amount required for the double talk determination processing can be reduced, and the accuracy of the double talk determination can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram of a mobile phone echo suppression unit according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing the operation of the mobile phone echo suppression unit according to the first embodiment of the present invention.
FIG. 3 is a flowchart illustrating an operation of an echo suppression unit for a mobile phone according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st microphone 2 2nd microphone 3 Speaker 4 1st analog-digital (A / D) converter 5 2nd analog-digital (A / D) converter 6 Digital-analog (D / A) conversion Unit 7 First Noise Suppressor (NS)
8 Second noise suppressor (NS)
9 First low-pass filter (LPF)
10. Second low-pass filter (LPF)
11 Level Detector 12 First Amplifier 13 Second Amplifier 14 Double Talk Detector 15 Echo Canceller 16 Third Amplifier 17 Fourth Amplifier

Claims (11)

First and second microphones for collecting transmission voice;
First and second amplifiers respectively corresponding to the first and second microphones,
A speaker for outputting a received voice;
An echo suppression unit for a mobile phone comprising:
An echo suppression unit for a mobile phone, wherein an amplification factor of the first amplifier and an amplification factor of the second amplifier are set to values different from each other. The echo suppression unit for a mobile phone according to claim 1, wherein a distance from the first microphone to the speaker is set to be longer than a distance from the second microphone to the speaker. . A first microphone that collects the transmitted voice,
A second microphone that collects the transmitted voice,
A speaker for outputting a received voice;
A first amplifier for amplifying an output signal of the first microphone,
A second amplifier for amplifying the output signal of the second microphone,
A level detector that detects a level of the reception signal and emits a signal indicating the detected level;
Based on an output signal from the first and second amplifiers and a signal from the level detector, a call state of a mobile phone terminal device equipped with the mobile phone echo suppression unit is detected, and the detected call is detected. A double talk detector that emits a signal according to the state,
An echo canceller that removes an echo component included in a transmission signal output from the first microphone in accordance with a signal from the double talk detector,
With
An echo suppression unit for a mobile phone, wherein an amplification factor of the first amplifier and an amplification factor of the second amplifier are set to values different from each other. A third amplifier that amplifies the signal sent from the external decoder and sends it to the echo canceller,
A fourth amplifier that amplifies the transmission signal transmitted from the echo canceller according to the amplification factor instructed by the double talk detector, and transmits the amplified transmission signal to an external encoder.
The echo suppression unit for a mobile phone according to claim 3, further comprising: 5. The mobile phone echo according to claim 3, wherein a distance from the first microphone to the speaker is set to be longer than a distance from the second microphone to the speaker. 6. Suppression unit. Extracting a low-frequency component in the output from the first microphone, a first low-pass filter to output to the first amplifier,
A second low-pass filter that extracts a low-frequency component in an output from the second microphone and outputs the low-frequency component to the first amplifier,
The echo suppression unit for a mobile phone according to any one of claims 3 to 5, further comprising: A mobile phone terminal device equipped with the echo suppression unit for a mobile phone according to any one of claims 1 to 6. First and second microphones for collecting transmission voice;
First and second amplifiers respectively corresponding to the first and second microphones,
A speaker for outputting a received voice;
An echo suppression method in a mobile phone echo suppression unit comprising:
Amplifying the output signal from the first microphone in the first amplifier;
A step of amplifying the output signal from the second microphone according to an amplification factor different from an amplification factor when amplifying the output signal from the first microphone in the first amplifier. ,
A step of determining double talk based on output signals from the first and second amplifiers,
An echo suppression method comprising: Extracting a low-frequency component in the output from the first microphone, and outputting the low-frequency component to the first amplifier;
Extracting a low-frequency component in the output from the second microphone, and outputting the low-frequency component to the first amplifier;
The echo suppression method according to claim 8, further comprising: A first microphone that collects the transmitted voice,
A second microphone that collects the transmitted voice,
A speaker for outputting a received voice;
A first amplifier for amplifying an output signal of the first microphone,
A second amplifier for amplifying the output signal of the second microphone,
Based on the output signals from the first and second amplifiers, a double state that detects a call state of a mobile phone terminal device equipped with the present mobile phone echo suppression unit and issues a signal corresponding to the detected call state. A talk detector,
An echo canceller that removes an echo component included in a transmission signal output from the first microphone in accordance with a signal from the double talk detector,
A fourth amplifier that amplifies the transmission signal transmitted from the echo canceller according to the amplification factor instructed by the double talk detector, and transmits the amplified transmission signal to an external encoder.
An echo suppression method in a mobile phone echo suppression unit comprising:
Calculating a first average signal power of the transmission signal output from the first amplifier;
Calculating a second average signal power of the transmission signal output from the second amplifier;
A step of determining whether the difference between the first average signal power and the second average signal power is equal to or greater than a threshold,
When the difference between the first average signal power and the second average signal power is smaller than the threshold, adding a positive value to the value of the loss insertion counter of the double talk detector,
The value of the loss insertion counter is less than the threshold,
Updating the filter coefficients of the echo canceller,
Setting the amplification factor of the fourth amplifier to a value smaller than its initial value;
An echo suppression method comprising: A first microphone that collects the transmitted voice,
A second microphone that collects the transmitted voice,
A speaker for outputting a received voice;
A first amplifier for amplifying an output signal of the first microphone,
A second amplifier for amplifying the output signal of the second microphone,
Based on the output signals from the first and second amplifiers, a double state that detects a call state of a mobile phone terminal device equipped with the present mobile phone echo suppression unit and issues a signal corresponding to the detected call state. A talk detector,
An echo canceller that removes an echo component included in a transmission signal output from the first microphone in accordance with a signal from the double talk detector,
A fourth amplifier that amplifies the transmission signal transmitted from the echo canceller according to the amplification factor instructed by the double talk detector, and transmits the amplified transmission signal to an external encoder.
An echo suppression method in a mobile phone echo suppression unit comprising:
Calculating a first average signal power of the transmission signal output from the first amplifier;
Calculating a second average signal power of the transmission signal output from the second amplifier;
A step of determining whether the difference between the first average signal power and the second average signal power is equal to or greater than a threshold,
When the difference between the first average signal power and the second average signal power is equal to or greater than the threshold, determining whether the received signal level is equal to or greater than a threshold.
If the received signal level is equal to or higher than a threshold, a positive value is added to the value of the loss insertion counter of the double talk detector, updating of the filter coefficient of the echo canceller is stopped, and the fourth amplifier Setting the amplification factor to a value smaller than its initial value;
An echo suppression method comprising:

Images