In current Debian Sid / Wheezy, Skype sound output through pulseaudio is crackling and audio input is outright atrocious, i.e. crackling in the extreme. All other sound applications work just fine.
At the same time, sound in Debian Squeeze is ok and to my surprise, it also works well in current Ubuntu. So there must be some specific reason why Skype misbehaves on Sid / Wheezy.
My ~/.asoundrc goes:
So Skype uses pulseaudio, however, the result is very disappointing...
I have just followed the guidance for the first fix on this page and the sound now sounds great.
In file/etc/pulse/default.pa its necessary to substitute the line;
load-module module-udev-detect tsched=0