The music will be cancelled by the adaptive filter along with the signal coming from the far end. For example, if music that is playing in the near end space, it may be added to the far end input signal. The adaptive filter in the AEC block will remove any signal that is part of the far end in. This is absolutely necessary for clear, full duplex conversation over communication channel. The person at the far end hears only the local talker and not the echoes and reverberation from the far end in the near end space. For example, in the case of a hands-free system or speakerphone, adaptation pauses when a person speaks directly into the microphone. This allows sounds in to be added to the far end out. The filter pauses adaptation when it detects sounds in the acoustic path unrelated to the far end in. The signal is then (optionally) passed through a noise reduction function to produce the output, which is a known as the “Far End Out.” This signal is sent to a Residual Echo Cancellation block (RES) that further recovers the input signal. The AEC block also calculates a residual signal containing nonlinear acoustic artifacts. The output of the filter is then subtracted from the acoustic path signal to produce a “clean” signal output with the linear portion of acoustic echoes largely removed. The algorithm continuously adapts this filter to model the acoustic path. The AEC block is based on an adaptive FIR filter. The acoustic path consists of an amplifier/loudspeaker, an acoustic environment, and a microphone returning the signal to the DSP.
As shown in the diagram below, the sound coming from the remote person speaking, known as the Far End In, is sent in parallel to a DSP path and to an acoustic path. The Acoustic Echo Cancellation (AEC) block is designed to remove echoes, reverberation, and unwanted added sounds from a signal that passes through an acoustic space. Click here to return to the ADI Algorithms page
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