CN113035224B - Equipment for eliminating echo and improving audio quality - Google Patents
Equipment for eliminating echo and improving audio quality Download PDFInfo
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- CN113035224B CN113035224B CN201911251391.3A CN201911251391A CN113035224B CN 113035224 B CN113035224 B CN 113035224B CN 201911251391 A CN201911251391 A CN 201911251391A CN 113035224 B CN113035224 B CN 113035224B
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- 238000001914 filtration Methods 0.000 claims description 8
- 239000003990 capacitor Substances 0.000 claims description 7
- 238000004364 calculation method Methods 0.000 claims description 6
- 238000005070 sampling Methods 0.000 claims description 6
- 238000001228 spectrum Methods 0.000 description 23
- 238000010586 diagram Methods 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 230000005236 sound signal Effects 0.000 description 2
- 238000010183 spectrum analysis Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000002592 echocardiography Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000030279 gene silencing Effects 0.000 description 1
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10L21/00—Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
- G10L21/02—Speech enhancement, e.g. noise reduction or echo cancellation
- G10L21/0208—Noise filtering
- G10L21/0216—Noise filtering characterised by the method used for estimating noise
- G10L21/0232—Processing in the frequency domain
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10L21/00—Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
- G10L21/02—Speech enhancement, e.g. noise reduction or echo cancellation
- G10L21/0208—Noise filtering
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- 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
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10L21/00—Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
- G10L21/02—Speech enhancement, e.g. noise reduction or echo cancellation
- G10L21/0208—Noise filtering
- G10L2021/02082—Noise filtering the noise being echo, reverberation of the speech
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- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Computational Linguistics (AREA)
- Quality & Reliability (AREA)
- Health & Medical Sciences (AREA)
- Audiology, Speech & Language Pathology (AREA)
- Human Computer Interaction (AREA)
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Multimedia (AREA)
- Tone Control, Compression And Expansion, Limiting Amplitude (AREA)
- Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
Abstract
The utility model relates to an eliminate equipment that echo improved audio quality, it includes, audio processor, the digital-to-analog converter DAC who is connected with audio processor, the power amplifier who is connected with DAC, the loudspeaker of the audio frequency of playing outward that is connected with power amplifier, and with audio processor connect the first analog-to-digital converter ADC, first analog-to-digital converter ADC be connected with the microphone, still including lieing in voltage divider and the wave filter of being connected between power amplifier and the loudspeaker, with the second analog-to-digital converter ADC that voltage divider and wave filter are connected, second analog-to-digital converter ADC with audio processor connect.
Description
Technical Field
The present application relates to the field of audio processing technologies, and in particular, to an apparatus for eliminating an echo and improving audio quality.
Background
In the field of artificial intelligent audio entry and real-time call audio, an audio system needs to play and record simultaneously, so that the record can be recorded into the sound played by the current system simultaneously, and the recorded and played sound forms echo. To improve audio quality, the system acquires an echo signal and cancels the echo signal from the recorded signal. I.e. the recorded signal is subjected to echo cancellation processing. Furthermore, it is common in the art to involve a DAC: the digital-to-analog chip is a chip for converting digital signal input into analog signal output; and an ADC: the analog-to-digital chip is a chip for converting an analog signal input into a digital signal output.
In the existing design of an echo eliminating system, an audio processor carries out spectrum analysis on a recording signal and a playback signal, analyzes response intensity and spectrum distribution, and designs a digital filter according to the analysis result, wherein the digital filter allows a speaker to pass through a sound spectrum according to the real-time change of the comparison of the two signals, inhibits background noise, namely the playback spectrum, reduces the energy of the background noise, and achieves the effect of inhibiting echo. When a person speaks, the audio processor analyzes the signal and analyzes the frequency spectrum of the speaker, thereby inhibiting the echo.
However, in the current design of echo cancellation systems, the echo acquisition part is generally completed at the stage of the original audio digital signal of the playback signal, and the audio processor compares, analyzes and processes the frequency spectrum of the original audio digital signal of the playback signal and the recording signal. In fact, the original audio digital signal passes through the DAC and the amplifier, is played by the loudspeaker and then is recorded and sampled by the microphone, and the frequency spectrum of the playback signal actually recorded into the microphone is changed. Then, a digital filter designed according to the spectrum of the original audio digital signal of the playback signal is used to process the audio signal, so that the sound spectrum of the speaker is changed and the sound is distorted.
The difference of the playback signal acquired by the echo cancellation method and the actually recorded echo signal on the frequency spectrum results in low efficiency in echo cancellation processing and loss of effective signals recorded by a microphone.
Technical content
In order to solve the above problems, the present application provides a system for eliminating echo and improving audio quality, which is capable of collecting playback signals that are closest to the actually recorded echo signal spectrum.
The application provides a eliminate equipment that echo improved audio quality, it includes, audio processor, the digital-to-analog converter DAC who is connected with audio processor, the power amplifier who is connected with DAC, the loudspeaker of the audio frequency of playing outward that is connected with power amplifier, and with audio processor connect the first analog-to-digital converter ADC, first analog-to-digital converter ADC be connected with the microphone, still including lieing in voltage divider and the wave filter of being connected between power amplifier and the loudspeaker, with the second analog-to-digital converter ADC that voltage divider and wave filter are connected, the second analog-to-digital converter ADC with audio processor connect.
The voltage divider is located before the filter to divide the level of the obtained signal.
The playback signal obtained at the output end of the power amplifier is divided by the voltage divider, so that the level is reduced to be in accordance with the level standard range of the second analog-to-digital converter ADC.
The voltage divider at least comprises two divider resistors which are respectively a first divider resistor (R) 2 ) And a second voltage dividing resistor (R) 4 ) According to
Calculating to obtain a first divider resistance (R) 2 ) A second voltage dividing resistor (R) 4 ) Suitable two resistance values; VO + is the level value of the playback signal; VADC is a proper level value of the analog-to-digital converter ADC; r 2 Is the resistance value of the first divider resistor, R 4 Is the resistance value of the second divider resistor.
The VO + is usually 5V in voltage amplitude; according to the sampling voltage range of the analog-to-digital converter ADC, the voltage amplitude VADC is reduced to 1V; calculating to obtain R 2 、R 4 Suitable resistance values of 6.8K omega and 1.8K omega, respectively, may be selected.
The filter comprises an RC low-pass filter and/or an RC high-pass filter.
The RC low-pass filter is formed by designing a third resistor (R) 3 ) And a first capacitance (C) 6 ) A component for performing low pass filtering; the RC high-pass filter designs a third resistor (R) 3 ) And a second capacitance (C) 5 ) And (c) means for performing high-pass filtering.
The frequency response range of the microphone does not exceed 20 Hz-10 KHz.
According to the formula of cut-off frequency calculation
To obtain R 3 And C 6 And a 6.8K omega resistor and a 2.2nF proper capacitor are respectively taken to filter signals with the frequency higher than the cut-off frequency of 9.6 kHz.
According to the formula of cut-off frequency calculation
And obtaining a proper resistance value and a proper capacitance value, and filtering out signals with the cut-off frequency lower than 21.1 Hz.
The device collects playback signals from the front end of the loudspeaker, and the signal frequency spectrum after the compression and filtering processing is most similar to the echo signal frequency spectrum actually recorded into the microphone, so that the efficiency of eliminating echoes by the audio silencing processor is improved, and the sound frequency spectrum of a speaker is prevented from changing and the sound is prevented from being distorted.
Drawings
Fig. 1 is a block diagram of an audio device for playing and receiving sound, which is related to the prior art.
Fig. 2 is a block diagram of an apparatus for canceling echo and improving audio quality according to the present application.
Fig. 3 is a circuit diagram of a specific embodiment of the present application.
Detailed Description
As shown in fig. 1, in the current design of eliminating echo, an audio processor performs spectrum analysis on a recording signal and a playback signal, analyzes response intensity and spectrum distribution, and designs a digital filter, which passes the sound spectrum of a speaker according to the real-time change of the comparison between the two signals, suppresses background noise, i.e., the playback spectrum, reduces the energy thereof, and achieves the effect of suppressing echo. When someone speaks, the audio processor analyzes the signal and analyzes the speaker spectrum, thereby suppressing the echo.
In the new echo cancellation device according to the present application, as shown in fig. 2, the playback signal collected at the front end of the speaker has a frequency spectrum consistent with the sound spectrum of the speaker, the level of the signal is reduced to a level standard range conforming to the ADC chip by voltage division, and then a filter is designed to filter out signals other than the microphone frequency response according to the microphone frequency response. The collected playback signal is basically consistent with the actually recorded echo signal frequency spectrum, and the digital filter designed according to the collected signal can eliminate the echo signal in the recording signal more effectively, thereby avoiding the sound spectrum and sound distortion of the speaker caused by the digital filter due to the frequency spectrum difference. The device for eliminating the echo and improving the audio quality comprises an audio processor, a digital-to-analog converter (DAC) connected with the audio processor, a power amplifier connected with the DAC, a loudspeaker connected with the power amplifier and used for playing audio, a first analog-to-digital converter (ADC) connected with the audio processor, a voltage divider and a filter which are located between the power amplifier and the loudspeaker, and a second analog-to-digital converter (ADC) connected with the voltage divider and the filter, wherein the second analog-to-digital converter (ADC) is connected with the audio processor. The voltage divider is located before the filter to divide the level of the obtained signal. The playback signal obtained at the output end of the power amplifier is divided by the voltage divider, so that the level is reduced to be in accordance with the level standard range of the second analog-to-digital converter ADC.
In the circuit shown in fig. 3, the audio signal VO + is collected at the front end of the speaker at the rear end of the power amplifier, and the voltage amplitude is about 5V, and is reduced to about 1V according to the voltage sampling range of the ADC, and is passed through the divider resistor R 2 And R 4 VO + was divided, as shown in the following graph
Calculating to obtain R 2 、R 4 The resistances of 6.8K omega and 1.8K omega are respectively selected to be appropriate. And because the frequency response range of the common microphone can not exceed 20 Hz-10 KHz, the resistance R is designed to pass 3 And a capacitor C 6 The RC low-pass filter is used for low-pass filtering and the cutoff frequency calculation formula is used
To obtain R 3 And C 6 A 6.8K Ω resistor and a 2.2nF capacitor were used, respectively, to filter out signals above the cut-off frequency by about 9.6 kHz. And because the ADC chip samples the variable voltage, and the direct current is 0Hz on the frequency spectrum, the sampling is meaningless. Finally, a DC blocking capacitor C is required 5 (generally, a capacitor larger than 1uF is selected) to remove the DC level, and then the ADC is used for sampling.
In fact, C5 and R3 form an RC high-pass filter, and the calculation formula of the cut-off frequency can be also used
It follows that signals below the cut-off frequency of about 21.1Hz can be filtered out.
Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.
Claims (1)
1. The equipment for eliminating echo and improving audio quality comprises an audio processor, a digital-to-analog converter (DAC) connected with the audio processor, a power amplifier connected with the DAC, a loudspeaker connected with the power amplifier and used for playing audio, and a first analog-to-digital converter (ADC) connected with the audio processor, wherein the first ADC is connected with a microphone;
the voltage divider is positioned in front of the filter to divide the level of the obtained signal;
the playback signal obtained at the output end of the power amplifier is subjected to voltage division through the voltage divider, so that the level is reduced to a level standard range meeting the second analog-to-digital converter (ADC);
the voltage divider at least comprises two divider resistors which are respectively a first divider resistor (R) 2 ) And a second voltage dividing resistor (R) 4 ) According to
Calculating to obtain a first divider resistance (R) 2 ) A second voltage dividing resistor (R) 4 ) Two resistance values of (a); wherein, V O+ Is the level value of the playback signal; v ADC Is the level value of the analog-to-digital converter ADC; r 2 Is the resistance value of the first divider resistor, R 4 Is the resistance value of the second divider resistor;
V O+ the voltage amplitude is 5V; according to the sampling voltage range of the analog-to-digital converter ADC, the voltage amplitude V should be adjusted ADC Reducing to 1V; calculating to obtain R 2 、R 4 Respectively selecting resistance values of 6.8K omega and 1.8K omega;
the filter comprises an RC low-pass filter and/or an RC high-pass filter;
the RC low-pass filter is formed by designing a third resistor (R) 3 ) And a first capacitance (C) 6 ) A component for low-pass filtering; the RC high-pass filter designs a third resistor (R) 3 ) And a second capacitance (C) 5 ) Forming for high pass filtering;
the frequency response range of the microphone is not beyond 20 Hz-10 KHz; finally, a second capacitor (C) is needed 5 ) Removing the direct current level, and then entering a second analog-to-digital converter (ADC) for sampling;
according to the formula of cut-off frequency calculation
To obtain R 3 And C 6 Respectively taking a 6.8K omega resistor and a 2.2nF capacitor, and filtering signals with the cutoff frequency higher than 9.6 kHz;
according to the formula of cut-off frequency calculation
The obtained resistance value and capacitance value filter out signals with the cut-off frequency of 21.1 Hz.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911251391.3A CN113035224B (en) | 2019-12-09 | 2019-12-09 | Equipment for eliminating echo and improving audio quality |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911251391.3A CN113035224B (en) | 2019-12-09 | 2019-12-09 | Equipment for eliminating echo and improving audio quality |
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| CN113035224A CN113035224A (en) | 2021-06-25 |
| CN113035224B true CN113035224B (en) | 2022-08-26 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US6785382B2 (en) * | 2001-02-12 | 2004-08-31 | Signalworks, Inc. | System and method for controlling a filter to enhance speakerphone performance |
| CN2645177Y (en) * | 2003-08-27 | 2004-09-29 | 联想(北京)有限公司 | Sound box with microphone |
| CN105825862A (en) * | 2015-01-05 | 2016-08-03 | 沈阳新松机器人自动化股份有限公司 | Robot man-machine dialogue echo cancellation system |
| JP6821126B2 (en) * | 2017-05-19 | 2021-01-27 | 株式会社Ｊｖｃケンウッド | Noise removal device, noise removal method and noise removal program |
| CN110223707A (en) * | 2019-07-10 | 2019-09-10 | 青岛海信电器股份有限公司 | Display device |
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