Something I found that i don't think has been covered here:

Despite fiddling with the game's settings and trying the 'disable HW Vertex Processing' fix, I was still having ridiculous audio synch problems. It turns out that the game really doesn't like running at 120hz, as is the case with my main monitor. I dropped the refresh rate to 60, and the game works perfectly again.

Just thought I'd post this here in case anyone else is having the same problem and wondering why the regular fix doesn't solve it.

Is it possible to change the refresh rate without changing the monitor settings?

In the game's settings utility, there's a dropdown box to select your refresh rate on the graphics tab. So you don't have to change anything else.

Aw snap, I realized my refresh rate is already set at 60. It was worth a shot I guess.