Originally Posted by M00chness
It happened to a buddy of mines car but his was alot older (95 I think). It had something to do with his radio. THe speaker wires were picking up sounds from the enginge and it sounded exactly what you were describing but it didnt get louder as you increased the volume. He put heat wrap around the wires behind his dash and the noise was gone.
Maybe if he has an aftermarket radio. Honda wiring for there stock stereo isn't to bad. When I ripped all of mine out I look at how it was installed, All lose ends were capped and the ground was good.
Have you put in a new stereo? Is it getting louder over time, or is it the same tone through the RPM band?