"PulseAudio is a Linux sound server that, through abstraction
layers, promises a myriad of flexible audio features: combining
multiple sound cards into a single, multi-channel device, changing
output devices on the fly for running applications, even
redirecting input and output between machines over the network.
Sadly, though, it is usually used just as a bare-bones drop-in
replacement for older, buggier sound servers like ESD -- because
that is the most common use case, and because the PulseAudio
documentation and tools aren't caught up to the same level as the
underlying library. Full PulseAudio nirvana entails digging into
the project in depth, but you can at least get your feet wet over
the weekend, directing and even multicasting audio between Linux
machines on your local network.
"PulseAudio is the default sound server for most GNOME-based
desktop Linux distributions, so after installation, the GNOME
desktop's PulseAudio configuration should work with most
general-purpose applications that produce audio output.
Unfortunately there are always exceptions, most often among
dedicated multimedia apps that prefer to behave according to their
own configuration rules rather than broader standards. The list can
include video players like MythTV or MPlayer, or audio conferencing
tools like Skype. You should go ahead and install all of the
PulseAudio packages provided by your distribution -- particularly
paprefs, pavucontrol, and pulseaudio-utils."