@ ikir
The 16 bit sound has some problem I haven't looked into yet. You can switch to 8 bit sound: Bring down the console ('^' key) and enter
ahi_bits 8
snd_restart
This should "fix" the sound problems for now...
[edit]
There are two other variables: ahi_speed (either 11 or 22) can be used to set 11 KHz or 22 KHz, and ahi_channles (1 or 2) to set mono or stereo.