Sound problem on newer movies

I have been doing movies for the last couple years.
I ran into a problem that I don’t understand at all.
I recently did Bewitched.I used dvdfab decrypter.Then
burned it using 1click dvd copy.When we watched it we
could tell the sound was weird.One minute the sound was
fine then about 10 minutes later the sound would be lower.
It did it throughout the whole movie.Then i just did Christmas
with the Kranks and the same thing.I finally used Anydvd with
clone dvd2.I am stumped on this.
The media I am using is Taiyo Yuden and I use sony dru 710a
burner.This problem just started and it is only on the newest

could it be your dvd player? have you tried them in another player? one of my dvd players makes a crackling sound, but i know its not the movie. DVD players have sound control like a VCR.