FMOD - FMOD Studio is an audio middleware solution and engine for games.
OpenAL - OpenAL is a cross-platform 3D audio API appropriate for use with gaming applications and many other...
SoLoud - Easy to use, free, portable c/c++ audio engine for games.
Wwise - Game audio engine, designed to give artists more control and save programmers' time.
iVoxx - Leading hosted telephony provider, free calls
OpenAL Soft - OpenAL Soft is an LGPL-licensed, cross-platform, software implementation of the OpenAL 3D audio API.