After the recent system upgrade of my Debian x64 home desktop I’ve noticed Skype started to make creepy buzzzzzzz sound or no sound at all. The issue is caused by the new version of pulseaudio, 4.0. The workaround is to set environment variable PULSE_LATENCY_MSEC=30:
$ PULSE_LATENCY_MSEC=30 skype &>/dev/null &
Here is a thread devoted to this issue.