How to fix or reset sound in Ubuntu Linux

I usually play multimedia files which need sounds. But sometime a crashed multimedia application can cause the audio device not released properly. The effects vary, from repeating annoying sounds to no sound at all. If this happens, I usually restart the PC as restarting Alsa is not working.

Actually, to fix this, we should know that Linux (including Ubuntu) open device resource as files. This includes sound card device. So to know which processes or applications accessing the device, just use lsof command.

sudo lsof |grep pcm

All you need to do is, kill the process (sudo kill -9 and restart the Alsa

sudo /etc/init.d/alsa-utils restart

And if you use pulseaudio as in the latest Ubuntu, you must restart pulseaudio as a user (do not use sudo)

pulseaudio restart

This should works.

Source: http://manubuntu.blogspot.com/2009/03/reset-sound.html