So I recently replaced the factory deck with a BT single din, nothing special. And replaced the factory speakers with some kickers. Everything sounds great except for at low speeds you hear a whine through the speakers with increase in RPM. If I push the mute button it stops. this is in an 07 GMT900 w/t rcsb

 

Start by upgrading the 12v constant and ground wires to the headunit. Do not use the factory ground in the harness, run it to metal in the dash somewhere

 

Yep, grounding the head unit case to the crossmember in the dash behind the radio always fixed this for me.