Linux Sound Architecture

Advanced Linux Sound Architecture (ALSA)

Part of Linux Kernel  is a software framework that supported API for sound card device driver.

Example of rerouted sound

•   application->pulseaudio->ALSA->hardware

alsamixer:

A graphical mixer program for ALSA that used to adjust
adjust the volume and configuration.

reference:

1. http://www.alsa-project.org/main/index.php/Main_Page
2. http://en.wikipedia.org/wiki/PulseAudio
3. http://en.wikipedia.org/wiki/Advanced_Linux_Sound_Architecture