Yes it happens to me I think about 2-3 times in over 20 hours of gameplay so not very consistent. But like another poster said for some people it happens a lot for some maybe never.
It usually happens to me when I play user tracks. The music stays on but all ambience audio disappears.
Anyways its a bug. I'm surprised Rockstar didn't patch it yet considering how fast they patched Vice City. Maybe all their legal troubles have diverted their attention to their customers.
Yeah, R*'s been too busy, either with this or a diff game they have in the makings.
Anywho, one fix that many people do is change their eax.dll file. It works for some soundcards, mainly the soundblaster live lineup. Get a new eax.dll file hea: http://www.dll-files.com/dllindex/dll-files.shtml?eax
Now this fix diddn't work for me as I have a SB audigy gamer. For me I had to turn my hardware acceleration down to basic (making my soundcard an even more bigger waste of cash, lol..) so that the damn game would run without buzzing probs. Might also help with your dying sound.
Btw, r* released a patch finally, so go download it if ya want. Since my sound works fine I diddn't patch. It affects the ability to mod San Andreas, so until I get confirmation that www.mtasa.com works on patch v1.1 I won't update. If it does then I will.