ok i just bout a pioneer 434 dvd player today and quality is great it even plays burned vcds and svcds great!!

but heres my problem i went to the video store and rented some dvds and while i watched em at certain times the sound would get louder for a sec then go back to normal this happen about 10-20 times in the movie i was watchin, i tried anotha movie and the same thing happened and i know for sure the second movie wasnt even slightly scratched or dirty. i'm using the regualar composite (rca) audio connection on my dvd player going straight to my tv and i'm using a 3ft monster cable specially designed for audio use(costs like 40 bucks)..can any one help me with my problem??.....is it something in the dvd setting??? help