Hmm, this is nothing I've heard about before and I don't really know how to attack the problem, but we should try to figure out where in the chain it appears.
You don't have too high volume somewhere causing digital distortion?
Is the problem present is you try another sound card (e g USB headphones if you have any)?
If you run
pasuspender -- speaker-test -c 2 -t sine -D plughw:0
Hmm, this is nothing I've heard about before and I don't really know how to attack the problem, but we should try to figure out where in the chain it appears.
You don't have too high volume somewhere causing digital distortion?
Is the problem present is you try another sound card (e g USB headphones if you have any)?
If you run
pasuspender -- speaker-test -c 2 -t sine -D plughw:0
...is the sound still broken?