Strange humming noise coming from radio when the car is off
 

I have just noticed that when my car is off, i still hear a noise from the inside. I think it may be coming from radio. This happens when the car is off, and when i turned the radio off, then shut off the car, it still made that sound. Any theories? I haven't driven it since today because I was away at college for 3 months and my dad has been driving it.

Are you sure it's coming from the radio? Verify this by removing the radio fuse. I had a vehicle that would run the battery down quickly. After removing the fuse for the head unit, the battery draw would stop. Turns out the CD player motor was running all the time.

Do you know which fuse is the radio fuse? I heard it was either 20 or 21, and i tried pulling both and it still makes the sound; also i think it drained my battery because my car started yesterday and it won't start now

Right, 20 and 21, but also 40, a 7.5A fuse.