Possible Steam runtime incompatibility.
As I can no longer find ~/.local/share/Steam/, I'll assume you guys fixed up your end.
The other half of the issue is fixed upstream in pulse 1.7, adding ppa:ubuntu-audio-dev/pulse-testing to your sources resolves the issue in 15.10.
Closing, problem is solved on 16.04
Nothing extracted yet.
Pulseaudio crashes a lot when launching steam games on ubuntu 15.10 leaving the games without sound