Re: Helium and the vocal cords [off list]

[Carl Mungan <mungan@USNA.EDU>]

>        You've all see it, most of us have done it. You take a good gulp
> of helium and talk like Mickey Mouse for a half minute or so.
>
>         Naively, I've just said - speed of sound in helium is greater. End
> of story. But now that I think about it, the frequency of the vocal cords
> doesn't change, the frequency of the disturbance shouldn't change,
> therefore this must be a resonance effect in the trachea and mouth.
> The air column then selects the higher harmonics from the vocal cords,
> due the greatest speed of sound in the air cavity.
>
>         Does anybody have any pointers that might discuss this more?

Mark, I believe you've got it right. Here's a page I wrote on the topic:

http://usna.edu/Users/physics/mungan/Scholarship/DonaldDuckTalk.pdf

Cheers, Carl

ps: I tried the Australian site mentioned on the list, but couldn't get
through. Looks like the URL got messed up.

Carl E. Mungan, Asst. Prof. of Physics 410-293-6680 (O) -3729 (F)
     U.S. Naval Academy, Stop 9C, Annapolis, MD 21402-5040
mailto:mungan@usna.edu      http://usna.edu/Users/physics/mungan/