Re: IS this real science or a special effect?

In article <dldmr3t5o175gdpo69eathnlp0v3tk1dc0@[EMAIL PROTECTED]
>,
 Dave Farrance <DaveFarrance@[EMAIL PROTECTED]
> wrote:

> CharlesRCaplan@[EMAIL PROTECTED]
 wrote:
> 
> > ... The vibrations travel
> >through the air at their normal speed. when you inhale helium and then
> >speak the sound of your voice gets higher because the sound of your
> >vibrating vocal cords travels faster in helium than in air. With
> >sulfur hexafluoride it's the opposite, the sound of your vibrating
> >vocal cords travels slower making the sound deeper. ...
> 
> The speed of sound through the gas might well be different but it won't
> shift the frequency.

The frequency *is* dependent on the speed of sound in the gas. Increased 
density at 1atm pressure corresponds to decreased speed of sound.
 
> I'm not sure, but I presume that the density of the medium actually
> alters the frequency at which the larynx vibrates.  Or it might have
> something to do with the way that the overtones are filtered.

Don't forget that the larynx is just part of a resonant system along 
with the trachea, mouth and sinus cavities; all of which will be 
affected by the speed of sound of the gas that fills them.