Re: pinhole Re: Donald Duck & He

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From: Gene Thompson (gthompso@ccsf.cc.ca.us)
Date: Fri Dec 01 2000 - 13:14:20 PST 

Date: Fri, 1 Dec 2000 13:14:20 -0800 (PST)
From: Gene Thompson <gthompso@ccsf.cc.ca.us>
Subject: Re: pinhole Re: Donald Duck & He
Message-ID: <Pine.HPX.4.21.0012011312080.9314-100000@fog.ccsf.cc.ca.us>

Why would the speed through He be faster? Sound needs a medium to travel
through and the denser the medium the faster the speed of sound. With
equal amounts and equal volume, the He atoms are much smaller than the air
combo of nitrogen molecules, oxygen molecules, carbon dioxide, water
vapor, etc. The He balloon just has less stuff per unit space than what's
in the air balloon. So shouldn't the speed through He be slower???

Ellen Koivisto
George Washington High, SF

On Fri, 1 Dec 2000, rob lee wrote:

> I think there is a different explanation for this question:
>
> ********
> Question 2: Why haven't your students asked why a voice gets "Donald
> Ducky"
> when helium is inhaled?
>
> Same answer as with the helium balloon. Helium's mass is less than the
> mass
> of air we normally inhale. Hence, it is less dense.
>
> When exhaling helium (speech) passes over the vocal cords, the cords
> encounter a less dense gas and vibrate at a higher frequency.
> *********
>
> I should probably leave this to Dr. Paul ("It's more complicated than
> that."), but it seems to me that there is an alternative explanation for
> this phenomenom. The natural frequency of vibration for you vocal cords
> is not changed by the He, rather the medium in your resonant chambers,
> (sinuses, throat, mouth, et. al.) is now helium with a much faster speed
> of sound. Since the frequencies are the same with a faster speed of
> sound, the wavelengths change causing different resonant frequencies to
> be emitted.
>
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