I need help on my TV SPeakers Problem?

I bought an HCT Flat screen over the summer. (after working in a program) and 3 days later something happend to the speakers when i was playing a game, and it makes a crackling noise when ever i guess a high pitch noise comes up for example: when i throw a grenade on Gears 2. so what is wrong do i need a stereo system or what? because i have speakers but i have cable and i use my hdmi inputs and i dont know how to have my cable go into my stereo system and my hdmi to go into the system as well. right now i just have the speakers and subwoover going into my headphones and it still make crackling noise and if i have to buy a new tv i would but i dont want to waste this brand new one?? any suggestions? plzz