My sub sometimes makes noise when I get close to it or when I touch it. Have been wondering, is this normal? It is not the noise that comes out when you touch or move the cable, sorry don't know how to explain it properly.

No that is not normal. Can you give us some examples of what the noise sounds like.

Have you removed the small grounding screw on the back?

Nope, should I?

Do you know when microphones get closer to some speakers sometimes it makes some strident noises? Something like that I guess. I can't find the appropriate word to explain it. Sorry..

Removing the ground screw is worth a try. Perhaps there is some interference being picked up by the sub from a device in your room or on your person (cell phone for example).

I have to remove the grounding screw. If I don't I get a constant hum.

You were suffering from a ground loop. That would certainly solve it. It is a good idea for the OP to try this. I am still not certain what the OP is experiencing.

Feedback. He's getting feedback. Don't have a clue why.