Strange noises

Ive been hearing a loud howling noise when I turn on either me heat or A/C... Its constant and loud... When I turn off the heat or A/C it stops... But starts again when turned on again...
Scenerio: I had my heat on during the winter and was driving through a pot hole ridden street when I fell into a massive pot hole that shook the car... Fortunetly my rims and suspension held but the howlling started and I mean its loud! Whats the noise?

Its probably the blower motor. Take your glove box out and see if its the blower motor.

what do I look for on the blower motor? Will it show any signs of problems just by looking at it...? But I think your right about it being the blower motor because once I gave my glove box a good wack and the noise stopped... But I didnt use the heat for a few days and it started making the noise again....