Very poor sound quality in Team Fortress 2

[Riddley]

I've followed the tutorial on audio conversion, but in-game the music always sounds very bad with a lot of crackling/pops/noise/distortion (this is both on my own server and others). I downloaded the sample wave files, and the same problems occur.
In goldwave, the files sound perfectly fine.

Is there any reason for this type of distortion? Any way to fix it?

[Renegade]

Generally there is a limit to how much quality you can expect over the voice comm system, but if you think the playback is clearly under-par (i.e. you hear better output from other users), double-check your voice cvars have appropriate values (to view them in console, enter "cvarlist voice").