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i bought an outlet for a laptop, which connects to the cigarette lighter hole. when i plug my laptop into the outlet, even when the laptop isn't on, my speakers and sub make noise. when i move the outlet w/ the plug in it around the car, the noise level varies, particularly near the floor of the car than the seat of the car. what's happening? remember that my computer isn't on, it makes noise as soon as the plug is plugged in into the outlet

 
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What's likely going on is that the widget that's converting the car 12V DC to whatever is used by the laptop (usually a higher voltage) is floating the ground inconsistently causing ground to move up and down and interact with the radio power supply. That causes the noise when I use a voltage converter. To find out for sure, unplug the connector from the back of the laptop and see if the noise goes away. If it does, well, then it's the charging system in the laptop.

The fix is to buy a 12V-12V DC to DC converter. What it does is isolate the 12V car supply from the 12V on the side of the laptop adapter unit, preventing the noise from going back and forth.

Of course, you can always hot-wire a 12VDC to 110AC inverter into the spot just to the left of the lighter socket and use that. That should provide you the ability to use the main house adapter in your car, and will also completely isolate the two devices.

Let us know what you find finally fixes it. You can toss money at the problem, or turn down the radio.

huggy