The Principle of Echo Cancellation and Noise Suppression

- Oct 25, 2018-

In instant messaging applications, real-time voice communication between two parties or multiple parties is required. In high-demand occasions, external speakers are usually used for playback, which will inevitably produce an echo, that is, after one party speaks, through the other party's speaker. The sound is played, and then it is collected by the other party's microphone and sent back to him. If you do not deal with the echo, it will affect the call quality and user experience, and more serious will also form a shock, resulting in howling. So how do you implement echo cancellation technology?

Echo cancellation is to remove the sound played by the local speaker from the sound data collected by microphone after microphone collects the sound, so that the sound recorded by microphone is only the voice of the local user.

The traditional echo cancellation is based on hardware. The DSP processing chip is integrated on the hardware circuit. For example, our commonly used fixed telephones and mobile phones have special echo cancellation processing circuits. The use of software to implement echo cancellation has always been technically difficult.

Echo cancellation has become the standard way to provide full-duplex voice in instant messaging. Acoustic echo cancellation is a method of preventing remote sounds from returning by eliminating or removing audio signals from the far end picked up in the local microphone. This audio removal is done by digital signal processing. Echo cancellation technology is one of the typical applications of digital signal processing.

The basic principle of echo cancellation is based on the correlation between the loudspeaker signal and the multipath echo generated by it. The speech model of the far-end signal is established, which is used to estimate the echo and continuously modify the coefficients of the filter to make the estimated value more Approaching the real echo. Then, the echo estimate is subtracted from the input signal of the microphone to achieve the purpose of eliminating the echo.



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