This has been in movies, commercials, and TV shows. and this is something that even a guy named "Mister Issues" will not do, so i ask the Mythbusters.

This has been discussed before,

we ended up on tension, and compression comparitive to tension and extention of the vocal cords.

Muscular design, genetic heritage etc.

Even though it is a well know myth, I doubt that Adam and Jamie will test it, there is no one on the show that will put their stuff on the line for science. It would be to risky to try, someone could become starel. Even if they did it I do not think the F.C.C would allow it to be shown in the U.S.