Echo Cancellation is one of the most critical component that is required in order to be able and have a full-duplex phone communication. Echo Cancellation is not a “nice to have” component and trying to make a phone call without it can become a quality nightmare. In this post, we will summarize the different functionalities that should be addressed when designing and building a robust echo cancellation. For each of these functionalities, we will provide a brief description and a reference to the relevant blog post that contains more details.

Searching the echo path. This is probably the most crucial functionality that needs to be taken care when building an echo cancellation. The main requirement is to allow the algorithm to identify exactly after how many milliseconds the audio that is played to the speakers bounces back as an echo.

Echo invalidation. From time to time, the echo cancellation algorithm needs to invalidate previous decisions after observing a significant change in echo behavior. This has to be done with extra care making sure not to make wrong decisions.

Howling effect. Howling is most probably the most annoying affect that appears when echo gets out of control and becomes louder and louder. Every echo cancellation algorithm has to have the ability to detect and remove howling.

Saturation in audio might cause a significant degradation in the ability of an echo cancellation algorithm to provide optimal results since it artificially clips the natural audio signal.

Audio stream synchronization discuss the importance of synchronization between the two audio streams that are provided as input to the echo cancellation algorithm: the local audio stream captured from the microphone and remote audio stream that is played to the speakers.

Reverberation and specifically a very long one is also a big challenge for an echo cancellation algorithm that should be able to identify and cancel it.

If you are a developer of a communication device or communication software or you suffer from echo in your network/equipment you are invited to contact our experts that will be happy to help you analyze the root cause and recommend on the best solution.