PulseAudio

In brief, PulseAudio is a proxy for your sound applications.
In Debian, applications such as Flesh, Skype are based on  PulseAudio.
(Just know the name, but not study in depth.)


reference:

1. https://wiki.debian.org/en/PulseAudio#Various_problems_with_Skype_and_Wine
2. http://www.freedesktop.org/wiki/Software/PulseAudio/