CSpeex

Project Description
CSpeex is a C# port of the JSpeex project. It is an implementation of the Speex speech codec (Open Source/Free Software patent-free audio compression format designed for speech). It provides both the decoder and the encoder in pure C#.

You can find the version for both desktop applications and Silveright (including a demo for audio capturing).

View a live demo at: http://www.aldentorres.com/silverlight/proof-of-concept-for-silverlight-and-speex-microphone-capture/