[y-c-o-m-b]

I've been able to do it since I was a young child. One method is by activating the tensor tympani muscles and tensing the front of my neck from my jaw (while making a frowning type facial expression - aka make yourself look like a cardassian) - that's the best way I can describe it. There's another way that involves tensing the base of my skull. I can also move my ears, so I wonder if being able to move that muscle plays into this.