low noise when engine is idle or in gear

I just installed an Alpine head unit to my Acura RSX-S 05. When the engine is iddle or in gear, I hear a low noise in the speakers. If I accelerate it sounds like if I had a turbo engine in my car. The moment I turn off the engine, the sound goes away. Is this a bad ground problem? how can I fix it? I would appreciate your input. Thanks in advance. DAniel

let me tell you what I have done to try and track down the problem. I would check to see if you have any multiple grounds. it seems like the ground problem can come from opens in circuits and what not. In my 1991 Infiniti G20 I have a bad A/C Fan switch. I hope to have it swapped out with a brand new one from the dealer on Wednesday. I thought my problem was bad grounding on the headunit. This time it is not the case. I am having the same problem as you. Try taking away your ground and see what happens. good luck.Mark "Hamzter" Cinense

1991 Infiniti G20 w/JDM SR20DE

Eclipse CD8445

MTX Thunder 684

Polk DB6750

Polk DB6500

Optima Red Top in the Trunk

My friend had this problem and it turned out to be the head unit.  It was the ground on the RCA outputs was bad.