Sometimes upgrading sound drivers will help you fix an issue with your sound. There are several ways to upgrade your ALSA sound drivers.
First, some words of caution:
Make sure you only have one override of ALSA drivers installed at a time. Make sure you uninstall the previous override before trying a new one, otherwise it is unclear which version will take precedence.
Aside from the Ubuntu web, there are several guides and blog posts about how to download, compile, and install newer ALSA driver versions yourself. These guides are of varying quality. The solutions suggested below are simpler, so it should not be necessary to follow them.
The latest stable ALSA - simplest
Whenever a stable release of ALSA is released, the linux-backports-modules-alsa-[Ubuntu Release]-[Kernel Flavor] is updated. [Ubuntu-release] means "karmic", "lucid", "maverick" etc, and [Kernel Flavor] normally means "generic" (or "server" for Ubuntu server edition). So just download and install this package, reboot, and test.
Daily snapshot - hottest and latest
As a third option, DKMS packages can be constructed that automatically rebuilds themselves whenever a new kernel is installed. More information to come.