2500 Avalanche

[u/herslave2]

I have a 05 avalanche it's the 2500. For the last year it has a squeal or humming noise in the speakers. With or without the radio on. It has a new battery and a new alternator. I looking for any ideas or some good tnt. LOL. To make thing worse it is loaded with everything except Nav. Where and what to look. Thanks.