From Quake Wiki
|Saved to config.cfg:||yes|
Sets how far into the future to mix the sound. Every frame, the sound is mixed up to a certain point, under the assumption that the next frame will arrive before the entire mixed buffer of sound is played. So with the default value of 0.1 seconds, if your framerate dips below 10 fps, it will run off the end of the sound buffer and you'll get stuttering sound. To fix this, increase the value (e.g. a value of 0.2 will handle as low as 5 fps before stuttering). However, increasing the mixahead time means the CPU has to do that much more work mixing more sound (thus possibly lowering your framerate, defeating the purpose), so be reasonable.
|List of console variables | List of console commands|