VOLUME GOES IN AND OUT

Hey guys, while watching a movie, my volume will be normal, and then all of a sudden it either goes silent or so low that I cant hear what anyone is saying, and then maybe 10-15 seconds later it will return to normal… At first I thought that it was just the stream that I was watching, so I switched it and even tried watching other things, and it is still giving me this problem. If anyone could help me out here it would be GREATLY appreciated.
Thank yall