Adware? wtf

This scared the heck out of me the first time it happen–being 4am and completely slient–but all of a sudden my headphones where blasting with an inaudiable noise. I put my headphones on and lowered the volume; it was a movie trailer. Now this wouldn’t have been particularly strange if i were on any webpage (wav file) but i wasn’t. I didn’t think to much of it the first time it happened, but then it happened again for the second day in a row. I was thinking it was some kind of adware, so i ran ad-aware, and i came up with nothing in particular. Any know of anything like this happening. Also, the only new software that i’ve installed lately was Apache, mySQL, and php, so i doubt it’s a progam i’ve installed.