One of the major challenges in pre-processing lies in cancelling acoustic echo that marks the speakerphone operation. Although speaker-to-microphone coupling occurs in traditional PSTN telephony too, the echo is less annoying due to really low end-to-end latencies (<30 milliseconds round trip delay).
In IP networks, however, the delay tends to be much higher (>100 milliseconds in a typical case), which makes acoustic echo much more noticeable and hence aggravates the problem due to echo. Despite the fact that the cancellation of acoustic echo forms a cornerstone of voice quality assessment by users, much is not understood about the dynamics involving an acoustic echo canceller (AEC).
In this paper, we provide an introduction to various aspects of AEC including its generation and characteristics, primary quality metrics, challenges involved in implementation, the impact of hardware on AEC performance in a phone and some information on testing an AEC.
To read the paper in its entirety, click here.