Speex

Speex is an open format, open source audio compression format created specifically for voice recordings.
The objective of this project is to tear down barriers between voice-related applications by creating a free alternative to costly proprietary solutions.
It is used in VoIP (Voice over Internet Protocol), in audio books, for internet and data archiving (for example in voicemail).

The project has become part of the Xiph.org foundation.

Speex∞
Xiph.Org Foundation∞