videos on my ipod... ?

i transferred videos from my phone to my computer then put them on itunes and 'converted' them for my ipod. when i tried to watch them today the picutre quality was fine but the sound was dodgy!! i could just hear what was going on but there was a weird bubbley type noise going on when any noise was made. it sounded how you would expecet people talking underwater to sound. by the way, my music plays fine on there.

any ideas whats up with this?

thanks