I have a similar thing that happens in AH (the only game I play 

 ) where I'll be flying along and suddenly the outside wind noise becomes super-amplified for like a half of a second, which can sometimes cause me to jump three feet out of my chair.  It started happening after I changed to my current system.  But the sound doesn't loop and there aren't any other ill-effects that I've seen so far.  It's just weird.
AMD 2700 Athlon XP 2.0GHz
512DDR RAM 
Asus A7N8X nForce chipset
GeF4 Ti4600 128MB 
Onboard nForce sound (with acceleration turned down a notch)