BCT thru metal plate

Here is a quote about an installation I read about on Slashdot when I was googling bone-conductive technology (Here is the full thread).I was actually trying to find out which bones of the body sound could be conducted through, but I haven't been able to figure that out:

"I saw an exhibit with this kind of technology about 10 years ago in a science museum. In their variation, you put your forehead on a postage-stamp sized metal plate, and then you suddenly heard a voice. I remember thinking that it was pretty cool. Definitely a good idea to put it in a cellphone headset. I do wonder a bit about ensuring sufficient contact with the jaw. In the exhibit I saw, you bent over to put your head on the plate, and thanks to the heaviness of the human head, there was a decent amount of pressure against the plate. No idea exactly how much you need to make sure it gets transferred to the bone, but I could see that being a bit of an issue.

If you combined that with the sub-vocalization technology that can detect what you say as you speak silently, we might be able to rid society of noisy cellphone users. Now that's tech I can appreciate."

sub vocalization technology? that sounds cool...