Why can I pop my eardrums at will?

I can pop my eardrums at will... I have been for a long time I'm almost 15 now.. My mom doesn't believe me because she can't do it. Now ill try to explain it.. It feels like I can just move something inside my ear and it makes my ears pop and it hear the crackling sound and everything. And If I like.. Hold the thing I move in place my ear stays popped the whole time and every sound I make is like amplified several times. My friend claims he can do it too.. Dunno how to prove it. Anyone know what this is?