All of a sudden, my pc has become silent.
It's not the speakers, because I tried changing them. It's difficult to see that it could be the (admittedly notorious) software, because I hadn't made any changes before it happened.
That leaves the sound chip on the motherboard. The only puzzle is that I'm not getting any error reported. There's nothing in the system log, and when I try running mplayer or rhythmbox from the command line, they make no complaint: whatever's wrong, they don't detect it.
Does anyone have any ideas? Is it possible to check the hardware using software?