noise through speakers

i've recently hooked up a pioneer inno satellite radio. i hard wired it to my head unit and plugged it in to my lighter plug. when it is running off of the radio's own battery power, i get no noise at all and it sounds great. when i plug it in the lighter plug to use the car's battery, i get a whining noise. it makes no difference if the car is running or not. i've tried using a ground loop isolator, no luck. i've also tried using an inline power noise filter, no luck. it's a constant noise and not like alternator whine. i've also tried grounding it in three different spots. can anybody help me??

what kind of vehicle is it? Hard wired ? Meaning with the fm adaptor? could be a bad ground on the car itself. I have also seen this happen with a bad battery or old battery.

it is a hyundai santa fe. i have it hooked direcly to the head unit from the xm radio using rca cables. i'm using 3 optima yellow top batteries on my car, and they're fine. i dont get the noise when i'm listening to a cd or anything else.

alternator whine... your cig lighter prolly has a bad ground

gotya! Try hardwiring the power to the back of the headunit and see what happens. gotta be a ground issue. Not necessarly (sp) altenator whine being it does it with the vehicle off

i just tried hooking the power and ground off of the same wires that the head unit is hooked to. i used a 3-way connector to do it and i still get the same problem.