Since I've seen a few noise posts here lately I just remembered an issue with my car. I actually noticed it the day I got it but am not sure what causes it. I turn on the ignition, radio off, windows shut, AC and all fans are off. I hear an ever so quiet noise that resembles a gas leak sound but also sounds like a set of speakers when you turn them on with no music, you know that ffffff noise. Its all around and I can't pinpoint it to any one places, so perhaps it is the speakers even though the radio is off?