You guys are most likely getting alternator whine, especially with aftermarket equipment. A ground loop isolator will fix this.

 

Is there a particular one to buy?

 

Check your ground and try different ground location first. Ground loop isolator will also add distortion to your sound system.

 

Sure check your wiring first. Also, if your stereo/amplifiers are aftermarket you need to run your power wires on different sides of the car. This is a harder install but helps against whine / interference.

Many many people use isolators with great success and no noticeable increase in distortion. I sold car audio for a few years back in the day, I never had people return them. Do a google search and read reviews. Keep in mind you can pick up an isolator for $20 or so from Best Buy or Radio Shack. If you don't like it or it doesn't help it's easy to return.

 

The OP has a stock stereo...there is no need for a ground loop!

 

correct, with me having a stock radio and amp i shouldnt have to add a isolator mine problem is gonna be a bad ground somwhere. gonna look at it this weekend and ill get back on to post what i find.

 

i if bang the dash board above the radio the noise stops. i ordered radio tools to get the radio out pretty sure its gonna be a bad/loose ground in there somewhere. ill let you guys know what i find when i get the radio out.