Sound overlapping problems in WOW, Please help

I have triplehead2go and im running 2 instance. One on each monitor and i use the 3rd to surf while im playing(thottbot). The issue is when i use sound on instance it seems to overlap and it comes out all gargly if thats a word. I try disabling sound on one instance and put sound on the other insance but it still overlaps. Not sure what to do any help would be much appreciated.

I have all sound off on all comps cept for my main .. not sure if that's what you said you tried

turn off background sounds.

it can also help to turn off hardware acceleration

Thanks for the replys ill try what you guys said.