problems with sub

[prockc7]

my sub just recently began to act up. it had quit working one night while i was out, when i got it to work again the next day, it had a continuous noise coming out of it, nothing even remotely close to the music being played through the stereo. when the car is started, it seems the frequency comeing out of the sub is in tune with the engine's rpm's. i have checked all the wiring conections and they seem fine. if anyone knows what this could be, i would be very pleased.

if it makes any difference, i have a pioneer premier 3004spl sub with a fosgate 501bd and and 1 farad capacitor.