All you need to know about acoustic echo cancellation

by Puneet Gupta and Anil Kumar, TechOnline India - March 26, 2009

While the future of telephony is clearly IP based, acoustic echo still undermines speakerphone operation. Ittiam Systems provides an introduction to various aspects of acoustic echo cancellation, 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.

While IP telephony is gaining popularity and is the direction towards the future, it comes with its own set of challenges. For example, there are multiple issues, such as jitter and packet loss management that come into the picture for dealing with 'IP' (or network) part of the ecosystem. Also, there is a whole cluster of pre/post processing challenges that one needs to face to provide an overall quality solution.

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.

Comments

blog comments powered by Disqus