acoustic echo cancellation (mobile communications) (AEC)

Acoustic Echo Cancellation(AEC) is a method of compensating for echoes, reverberation and disturbing noises in acoustic signals. In the AEC process, interferences that occur in a room are removed from audio signals.

For acoustic echo cancellation, electronic circuits are available with which echoes, reverberation and other acoustic impairments in the audio signal are compensated and do not reach the receiver. Without echo cancellation, an unnatural sound would be produced and the interference would significantly impair speech intelligibility.

Conceptually, AEC circuits consist of a signal path through which a person's speech signal is transmitted to the loudspeaker. The loudspeaker signal, which reflects off the walls of the room, is picked up by a microphone and transmitted via the second signal path. Both signal paths - the one to the loudspeaker and the one from the microphone - are interconnected by an Adaptive FIR Filter, whose algorithm continuously adapts the filter to the acoustic conditions. The Adaptive FIR Filter is the core component of the AEC circuit. The interfering signal detected by the FIR is subtracted from the audio signal to compensate for the interference.

The implementations for acoustic echo cancellation are optimized for speech. The bandwidth standard is narrowband with a bandwidth of 4 kHz and a sampling rate of 8 kHz, wideband with 8 kHz bandwidth and 16 kHz sampling rate, and ultra-wideband with 16 kHz bandwidth and 32 kHz sampling rate. AEC technology is used in voice communications and hands-free devices.