alsa
Get flash to fully experience Pearltrees
pulseAudio
You may want to follow this guide to gather essential troubleshooting information about your sound card. This information will be useful in posting a question to launchpad and getting help from volunteers who are monitoring the Launchpad forums: The various different pages about sound issues each serve a different purpose or different tastes. OpenSource systems are about freedom OF choice so it's good that people are able to choose which pages they use.
SoundTroubleshootingProcedure - Community Ubuntu Documentation
SoundTroubleshooting - Community Ubuntu Documentation
As of 2012, much of the information on this page is outdated. Please refer to the official sound debugging guide and Ubuntu Audio Development team's pages for more up-to-date information. Note: In some cases, the procedures listed below are not "simple fixes" and can cause problems later if the card needs to be replaced. It may be easier to simply replace or add a new card from the start rather than risk damaging the installation. Cards that work the best with Ubuntu are called "free software compatible."
I couldn't get PulseAudio to work on one of my computers no matter what I do. But removing PulseAudio can be tricky and besides, there is a very easy way to "fix" it (if you're using GStreamer as a backend for music and videos). This is very useful for applications which use GStreamer but do not let you select the sound output module like: Rhythmbox, Totem and so on. Then navigate to /system/gstreamer/0.10/default and change the "audiosink" and "musicaudiosink" to "alsasink" or "osssink", depending on what you want to use. I for one used OSS ("osssink" - notice there are 3 s) because it simply works, even though it's deprecated. The above 2 commands set GStreamer to use OSS for audio and video players.
How To Replace PulseAudio With ALSA Or OSS In A Few Seconds [Ubuntu Linux - GStreamer] ~ Web Upd8
altFIRE
Oh the fun! I removed package pulseaudio from my system this morning and reverted to alsa , thinking this would fix my sound lag problems on Doom 3 and Quake 4 . It did, BUT... sound stopped working in Quake 2 , Quake 3 , Open Arena , Urban Terror etc etc. I was able to fix it eventually, but learned from my mistakes.