sorry for the lack of wisdom, but could somebody tell me what port noise sounds like? Because I just put my system in my car and unless i have the volume turned down to zero, my sub is constantly playing kinda loudly. Could this be how the amp settings are set?

your telling me that when your radio is all the way down your sub still has a noise?

if you turn your radio off all togather, does it still sound?

what about with the car off but the radio on, but at zero?

what kinda amp, stereo and do you have any EQ's cross overs or LOC's inline to your sub?

port noise is a chuffing type sound...port noise is just air rushing in and out.

you are probably getting feedback

check your wiring, most likely your rca cables. Unplug them, turn on the stereo and if theres no sound at all then you found it. Replace them or ground them.