CN106911872B - Method and device for reducing echo cancellation residue - Google Patents
Method and device for reducing echo cancellation residue Download PDFInfo
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- CN106911872B CN106911872B CN201710092405.6A CN201710092405A CN106911872B CN 106911872 B CN106911872 B CN 106911872B CN 201710092405 A CN201710092405 A CN 201710092405A CN 106911872 B CN106911872 B CN 106911872B
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- H04M9/00—Arrangements for interconnection not involving centralised switching
- H04M9/08—Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic
- H04M9/082—Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic using echo cancellers
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Abstract
The invention provides a method and a device for reducing echo cancellation residue.A far-end sound signal passes through a filter and then drives a loudspeaker and an echo canceller, and the type of the filter is determined by the relation characteristic of total harmonic distortion and frequency of the loudspeaker. When the filter is a high-pass filter, the cut-off frequency of the filter is smaller than a first frequency and larger than a second frequency, and the first frequency is larger than the second frequency; when the filter is a low-pass filter, the cut-off frequency of the filter is greater than the first frequency and less than the second frequency, and the first frequency is less than the second frequency. The aim is to have a transition band of the filter amplitude-frequency characteristic between a frequency at which the sound pressure level of the loudspeaker deteriorates significantly with frequency and a frequency at which the total harmonic distortion deteriorates sharply with frequency. The method simply and effectively reduces the influence of the nonlinear distortion of the loudspeaker on the echo cancellation on the premise of not obviously influencing the sound quality, and improves the quality of the transmitted sound.
Description
Technical Field
The present invention relates to the field of echo technology, and in particular, to a method and apparatus for reducing echo cancellation residual.
Background
In an audio system, echo interference is inevitable due to the existence of signal reflection paths. Echoes in audio communications include electrical echoes caused by signal energy reflections caused by impedance mismatches and acoustic echoes; acoustic echo refers to sound played by a speaker at the receiving end that is picked up by a microphone and transmitted back to the speaking end, and includes direct echo and indirect echo. Direct echo is sound that enters the microphone directly after being played by the speaker, and indirect echo is sound that enters the microphone after being reflected once or more times by different paths (such as any object in a house). The echo is delayed by a channel and then transmitted back to the speaking end and heard by the speaker, thereby causing interference to the audio frequency of the speaking end, reducing the definition of the audio frequency and influencing the communication quality of the audio frequency.
With the development of communication technology, more and more multimedia devices are accessed to the internet. More and more networks provide instant voice communication functionality. For full-duplex instant voice communication, echo cancellation is an indispensable function without using headphones. The effect of echo cancellation directly affects the user experience. The parameter ERLE, which measures the echo cancellation effect, indicates the residual after echo cancellation, which directly reflects the echo cancellation effect. Among the many factors that cause residue, nonlinear distortion is the determining factor. Minimizing the adverse effects of nonlinear distortion generated in an echo cancellation system is therefore critical to success or failure of echo cancellation.
Disclosure of Invention
The present invention provides a method for reducing echo cancellation residual, so as to suppress the nonlinear distortion generated by the speaker, and further effectively reduce the final residual echo in the echo cancellation system.
In order to achieve the above object, the present invention provides a method for reducing echo cancellation residual, comprising:
after passing through a filter, the sound signal of the far-end equipment is input to a loudspeaker to drive the loudspeaker, and is simultaneously input to an echo canceller as a reference signal of the echo canceller; and
the echo of the loudspeaker and the sound signal of the near-end equipment are input to the echo canceller after passing through a microphone and then are transmitted to the far-end equipment.
Preferably, in the above method for reducing echo cancellation residual, the type of the filter is determined according to a characteristic of a relationship between total harmonic distortion and frequency of the speaker.
Preferably, in the above method for reducing echo cancellation residual, when the filter is a high-pass filter, a cut-off frequency of the filter is smaller than a first frequency and larger than a second frequency, wherein the first frequency is a frequency at which a sound pressure level of the speaker starts to decrease sharply with decreasing frequency, the second frequency is a frequency at which total harmonic distortion of the speaker starts to increase sharply with decreasing frequency, and the first frequency is larger than the second frequency.
Preferably, in the above method for reducing echo cancellation residual, when the filter is a high-pass filter, a cutoff frequency of the filter is equal to or lower than a first frequency, where the first frequency is a frequency at which a sound pressure level of the speaker starts to decrease sharply as the frequency decreases, the second frequency is a frequency at which total harmonic distortion of the speaker starts to increase sharply as the frequency decreases, and the first frequency is equal to or lower than the second frequency.
Preferably, in the above method for reducing echo cancellation residual, when the filter is a low-pass filter, a cut-off frequency of the filter is greater than a first frequency and less than a second frequency, wherein the first frequency is a frequency at which a sound pressure level of the speaker starts to decrease sharply as the frequency increases, the second frequency is a frequency at which total harmonic distortion of the speaker starts to increase sharply as the frequency increases, and the first frequency is less than the second frequency.
Preferably, in the above method for reducing echo cancellation residual, when the filter is a low-pass filter, a cutoff frequency of the filter is equal to or higher than a first frequency, where the first frequency is a frequency at which a sound pressure level of the speaker starts to sharply decrease as the frequency increases, the second frequency is a frequency at which total harmonic distortion of the speaker starts to sharply increase as the frequency increases, and the first frequency is equal to or higher than the second frequency.
Preferably, in the method for reducing echo cancellation residual, the echo canceller includes a linear echo canceller.
The invention also provides a device for reducing echo cancellation residue, comprising:
the filter is used for receiving the sound signal of the far-end equipment, filtering the sound signal and inputting the filtered sound signal into a loudspeaker and an echo canceller;
the loudspeaker is used for receiving and playing the sound signal of the remote equipment after the filtering processing of the filter;
an echo canceller for cancelling the echo of the loudspeaker when transmitting an acoustic signal emitted by a microphone of a near-end device.
Preferably, in the above apparatus for reducing echo cancellation residual, the type of the filter is determined according to a characteristic of a relationship between total harmonic distortion and frequency response of the speaker.
Preferably, in the above apparatus for reducing echo cancellation residual, when the filter is a high-pass filter, a cut-off frequency of the filter is smaller than a first frequency at which a sound pressure level of the speaker starts to sharply decrease as the frequency decreases and is larger than a second frequency at which total harmonic distortion of the speaker starts to sharply increase as the frequency decreases, and the first frequency is larger than the second frequency.
Preferably, in the above apparatus for reducing an echo cancellation residual, when the filter is a high-pass filter, a cutoff frequency of the filter is equal to or lower than a first frequency, where the first frequency is a frequency at which a sound pressure level of the speaker starts to sharply decrease as the frequency decreases, the second frequency is a frequency at which a total harmonic distortion of the speaker starts to sharply increase as the frequency decreases, and the first frequency is equal to or lower than the second frequency.
Preferably, in the above apparatus for reducing echo cancellation residual, when the filter is a low-pass filter, a cut-off frequency of the filter is greater than a first frequency at which a sound pressure level of the speaker starts to sharply decrease as the frequency increases and is less than a second frequency at which total harmonic distortion of the speaker starts to sharply increase as the frequency increases, and the first frequency is less than the second frequency.
Preferably, in the above apparatus for reducing echo cancellation residual, when the filter is a low-pass filter, a cutoff frequency of the filter is equal to or higher than a first frequency, where the first frequency is a frequency at which a sound pressure level of the speaker starts to sharply decrease as a frequency increases, the second frequency is a frequency at which total harmonic distortion of the speaker starts to sharply increase as a frequency increases, and the first frequency is equal to or higher than the second frequency.
In the method and apparatus for reducing echo cancellation residual provided by the present invention, a far-end sound signal passes through a filter and then drives a speaker and an echo canceller, and the type of the filter is determined by the relationship between the total harmonic distortion and the frequency of the speaker. When the filter is a high-pass filter, the cut-off frequency of the filter is smaller than a first frequency and larger than a second frequency, and the first frequency is larger than the second frequency; when the filter is a low-pass filter, the cut-off frequency of the filter is greater than the first frequency and less than the second frequency, and the first frequency is less than the second frequency. The method aims to ensure that a transition band of the amplitude-frequency characteristic of the filter is positioned between the frequency of the loudspeaker with the sound pressure level obviously deteriorated along with the frequency and the frequency of the loudspeaker with the total harmonic distortion sharply deteriorated along with the frequency.
Drawings
Fig. 1 is a diagram illustrating the result of the apparatus for reducing echo cancellation residual according to the embodiment of the present invention.
Detailed Description
The following describes in more detail embodiments of the present invention with reference to the schematic drawings. Advantages and features of the present invention will become apparent from the following description and claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
An embodiment of the present invention provides an apparatus for reducing echo cancellation residual, as shown in fig. 1, where fig. 1 is an apparatus for reducing echo cancellation residual. Specifically, the apparatus comprises: a filter, a speaker, an echo canceller, and a microphone. The filter is configured to receive a sound signal of a far-end device, filter the sound signal received by the filter, and input the sound signal to the speaker and the echo canceller, the speaker is configured to receive and play the sound signal of the far-end device filtered by the filter, the microphone of the near-end device is configured to receive an echo of the sound signal of the far-end device filtered by the filter and a sound signal of the near-end device played by the speaker, and send the received echo and sound signal to the echo canceller, and the echo canceller cancels the echo mixed in the sound signal of the near-end device and sends the echo to the far-end device.
The present embodiment further provides a method for reducing echo by using the above apparatus for reducing echo cancellation residual, specifically, the method includes: after passing through a filter, the sound signal of the far-end equipment is input to a loudspeaker to drive the loudspeaker, and is simultaneously input to an echo canceller as a reference signal of the echo canceller; the echo of the loudspeaker and the sound signal of the near-end equipment are input to the echo canceller after passing through a microphone and then are transmitted to the far-end equipment.
The device for reducing echo cancellation residue can be used for a remote wireless visual system, and in the embodiment, a wireless visual doorbell system is taken as an example and is used for a building security system. The device of the indoor part of the wireless visual doorbell system is used as a near-end device, and the device of the gate part of the building is used as a far-end device. The near-end device is the device for reducing the echo cancellation residual in the embodiment of the invention. The specific method comprises the following steps: and after receiving the sound signal of the far-end equipment, the filter filters the sound signal, and after performing first conditioning on the filtered sound signal, the filter sends the sound signal to the loudspeaker. The first conditioning includes amplifying, modulating, etc. the filtered sound signal so that the first conditioned sound signal is adapted to drive the speaker.
Meanwhile, the sound signal filtered by the filter is input to the echo canceller as a reference signal of the echo canceller so as to eliminate adverse effects caused by nonlinear distortion of the loudspeaker. Similarly, the second conditioning is performed before the second conditioning is input to the echo canceller, where the second conditioning includes processing such as amplifying and modulating the filtered sound signal, so that the second conditioned sound signal is adapted to drive the echo canceller.
And the echo of the loudspeaker and the sound signal of the near end enter an indoor microphone to form a mixed sound signal, and the mixed sound signal is subjected to third conditioning and then input to the echo canceller to cancel the echo of the loudspeaker. And transmitting the sound signal after the echo of the loudspeaker is cancelled to a remote device of a building gate. The third conditioning includes amplifying, modulating, etc. the mixed sound signal to adapt it to drive the echo canceller.
It should be noted that, in the present embodiment, the echo canceller includes, but is not limited to, a linear echo canceller.
Further, the type of the filter is determined according to the frequency dependence characteristic of the total harmonic distortion of the loudspeaker. In the frequency range of 0 to 20000Hz, if there is a frequency from which the total harmonic distortion starts to increase sharply with decreasing frequency, the filter should be a high pass filter. If there is a frequency from which the total harmonic distortion increases sharply with increasing frequency, the filter should be a low pass filter. If both of these conditions exist, the filter should be a band pass filter.
Specifically, when the filter is a high-pass filter, the cut-off frequency of the filter is obtained by the following formula:
f2＜fcut-off＜f1(formula 1)
Wherein f isCut-offRepresenting the cut-off frequency, f, of said filter1Representing a first frequency, f2Representing a second frequency.
In particular, the first frequency f1The second frequency f is the frequency at which the sound pressure level of the loudspeaker starts to drop sharply with a drop in frequency2At a frequency at which the total harmonic distortion of the loudspeaker begins to rise sharply as the frequency decreases, at which time f2＜f1。
However, when f2≥f1The cut-off frequency of the filter is obtained by the following formula:
fcut-off≤f1. (formula 2)
The method aims to ensure that a transition band of the amplitude-frequency characteristic of the filter is positioned between the frequency of the loudspeaker with the sound pressure level obviously deteriorated along with the frequency and the frequency of the loudspeaker with the total harmonic distortion sharply deteriorated along with the frequency, simply and effectively reduces the influence of the nonlinear distortion of the loudspeaker on the echo cancellation on the premise of not obviously influencing the sound quality, and improves the quality of the transmitted sound.
When the filter is a low-pass filter, the cut-off frequency of the filter is obtained by the following formula:
f2＞fcut-off＞f1(formula 3)
Wherein f isCut-offRepresenting the cut-off frequency, f, of said filter1Representing a first frequency, f2Representing a second frequency.
In particular, the first frequency f1The second frequency f is the frequency at which the sound pressure level of the loudspeaker starts to drop sharply with increasing frequency2At a frequency at which the total harmonic distortion of the loudspeaker begins to rise sharply with a rise in frequency, when f2＞f1。
At that time, when f2≤f1The cut-off frequency of the filter is obtained by the following formula:
fcut-off≥f1. (formula 4)
The method aims to ensure that a transition band of the amplitude-frequency characteristic of the filter is positioned between the frequency of the loudspeaker with the sound pressure level obviously deteriorated along with the frequency and the frequency of the loudspeaker with the total harmonic distortion sharply deteriorated along with the frequency, simply and effectively reduces the influence of the nonlinear distortion of the loudspeaker on the echo cancellation on the premise of not obviously influencing the sound quality, and improves the quality of the transmitted sound.
In summary, in the method and apparatus for reducing echo cancellation residual according to the embodiments of the present invention, the far-end sound signal passes through a filter and then drives the speaker and the echo canceller, and the type of the filter is determined by a characteristic of a relationship between total harmonic distortion and frequency of the speaker. When the filter is a high-pass filter, the cut-off frequency of the filter is smaller than a first frequency and larger than a second frequency, and the first frequency is larger than the second frequency; when the filter is a low-pass filter, the cut-off frequency of the filter is greater than the first frequency and less than the second frequency, and the first frequency is less than the second frequency. The aim is to have a transition band of the filter amplitude-frequency characteristic between a frequency at which the sound pressure level of the loudspeaker deteriorates significantly with frequency and a frequency at which the total harmonic distortion deteriorates sharply with frequency. The method simply and effectively reduces the influence of the nonlinear distortion of the loudspeaker on the echo cancellation on the premise of not obviously influencing the sound quality, and improves the quality of the transmitted sound.
The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any way. It will be understood by those skilled in the art that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (11)
1. A method for reducing echo cancellation residual, comprising:
after passing through a filter, the sound signal of the far-end equipment is input to a loudspeaker to drive the loudspeaker, and is simultaneously input to an echo canceller as a reference signal of the echo canceller; and
echo of the loudspeaker and sound signals of the near-end equipment pass through a microphone and then are input into the echo canceller, and then are transmitted to the far-end equipment;
wherein the type of the filter is determined according to the relation characteristic of the total harmonic distortion and the frequency of the loudspeaker.
2. The method of claim 1, wherein when the filter is a high pass filter, a cut-off frequency of the filter is less than a first frequency and greater than a second frequency, wherein the first frequency is a frequency at which a sound pressure level of the speaker starts to decrease sharply as the frequency decreases, the second frequency is a frequency at which a total harmonic distortion of the speaker starts to increase sharply as the frequency decreases, and the first frequency is greater than the second frequency.
3. The method of claim 1, wherein when the filter is a high pass filter, a cutoff frequency of the filter is equal to or less than a first frequency, wherein the first frequency is a frequency at which a sound pressure level of the speaker begins to sharply decrease as the frequency decreases, wherein a second frequency is a frequency at which a total harmonic distortion of the speaker begins to sharply increase as the frequency decreases, and wherein the first frequency is equal to or less than the second frequency.
4. The method of claim 1, wherein when the filter is a low pass filter, a cut-off frequency of the filter is greater than a first frequency and less than a second frequency, wherein the first frequency is a frequency at which a sound pressure level of the speaker starts to decrease sharply as the frequency increases, the second frequency is a frequency at which total harmonic distortion of the speaker starts to increase sharply as the frequency increases, and the first frequency is less than the second frequency.
5. The method of claim 1, wherein when the filter is a low pass filter, a cut-off frequency of the filter is equal to or greater than a first frequency, wherein the first frequency is a frequency at which a sound pressure level of the speaker starts to decrease sharply as the frequency increases, wherein a second frequency is a frequency at which total harmonic distortion of the speaker starts to increase sharply as the frequency increases, and wherein the first frequency is equal to or greater than the second frequency.
6. The method of reducing echo cancellation residual according to claim 1, wherein said echo canceller comprises a linear echo canceller.
7. An apparatus for reducing echo cancellation residual, comprising:
the filter is used for receiving the sound signal of the far-end equipment, filtering the sound signal and inputting the filtered sound signal into a loudspeaker and an echo canceller;
the loudspeaker is used for receiving and playing the sound signal of the remote equipment after the filtering processing of the filter;
an echo canceller for cancelling an echo of the speaker when transmitting a sound signal emitted from a microphone of a near-end device;
wherein the type of the filter is determined according to the relation characteristic of the total harmonic distortion and the frequency of the loudspeaker.
8. The apparatus for reducing echo cancellation residual according to claim 7, wherein when said filter is a high pass filter, a cutoff frequency of said filter is less than a first frequency and greater than a second frequency, wherein said first frequency is a frequency at which a sound pressure level of said speaker starts to decrease sharply as the frequency decreases, said second frequency is a frequency at which total harmonic distortion of said speaker starts to increase sharply as the frequency decreases, and said first frequency is greater than said second frequency.
9. The apparatus for reducing echo cancellation residual according to claim 7, wherein when said filter is a high pass filter, a cutoff frequency of said filter is equal to or less than a first frequency, wherein said first frequency is a frequency at which a sound pressure level of said speaker starts to sharply decrease as the frequency decreases, wherein a second frequency is a frequency at which a total harmonic distortion of said speaker starts to sharply increase as the frequency decreases, and wherein said first frequency is equal to or less than said second frequency.
10. The apparatus for reducing echo cancellation residual according to claim 7, wherein when said filter is a low pass filter, a cutoff frequency of said filter is greater than a first frequency at which a sound pressure level of said speaker starts to sharply decrease as a frequency increases and less than a second frequency at which a total harmonic distortion of said speaker starts to sharply increase as a frequency increases, and said first frequency is less than said second frequency.
11. The apparatus for reducing echo cancellation residual according to claim 7, wherein when said filter is a low pass filter, a cutoff frequency of said filter is equal to or higher than a first frequency, wherein said first frequency is a frequency at which a sound pressure level of said speaker starts to sharply decrease as a frequency rises, a second frequency is a frequency at which total harmonic distortion of said speaker starts to sharply increase as a frequency rises, and said first frequency is equal to or higher than said second frequency.
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| CN110310654A (en) * | 2019-07-26 | 2019-10-08 | 歌尔科技有限公司 | Echo cancel method and device, electronic equipment, readable storage medium storing program for executing |
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| DE60317368T2 (en) * | 2003-01-08 | 2008-08-28 | Nxp B.V. | NONLINEAR ACOUSTIC ECHO COMPENSATOR |
| EP2575375B1 (en) * | 2011-09-28 | 2015-03-18 | Nxp B.V. | Control of a loudspeaker output |
| EP3080975B1 (en) * | 2013-12-12 | 2017-07-12 | Koninklijke Philips N.V. | Echo cancellation |
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