Reverberation, in audio processing, is an on-going echo after a sound is produced. To illustrate this phenomena let’s think of a simple scenario in which you call a friend that is using laptop without headsets. In this case your voice will be played by the speakers of the laptop and from the speakers your voice will be picked up by the microphone of the laptop. This is the first & direct route of echo but it is not the only route and there are many other indirect routes: from the speakers your voice will bounce between the furniture and walls and afterwards it will bounce to the microphone. As you can see, your voice will travel in different routes one direct route and many indirect routes. The outcome is that the microphone will pick up your voice not as sharp as the original but it will be smeared. The longer your voice is being smeared the bigger the reverberation is.

The duration of the reverberation depends on the environment. For example, if the environment does not contain material that can absorb and decay the sound but instead it has material, like metal, that will cause the sound to keep bouncing from one side to the other, the reverberation can be very long.

It is clear that echo in general and specifically long reverberation reduces the quality of the phone call and usually makes it intolerable. In real life, echo and reverberation are usually not a common issue due to two reasons:

1. Usage of headsets that physically block the echo from being generated.
2. Usage of echo cancellation software that remove the echo from the audio signal that is captured by the microphone.

Nevertheless, there are cases in which a basic echo cancellation software will fail and echo will be heard. This usually happens in extreme scenarios like the ones having long reverberation. In these cases, you should use a robust echo cancellation software that is equipped with robust algorithm that can detect and remove echo with long reverberation from the call.

For more information about the challenges of echo cancellation you are invited to read our blog post on echo cancellation – art or science.