IPhone 3GS sound help

[ConnorDAFC]

Hi,

Whenever i try to listen to music or watch a video, there is a problem which the voice or when they sing is too low and the music audio just drains it out (if that makes sense) and for the video its pretty much the same with the background sounds draining out the person talking. Also to add it only occurs when i listen through headphones or earphones but the headphones are fine because i checked with my old ipod and they worked fine.

Thanks