Dense Gas and Pitch
Date: July 2006
This question has to do with a previous question,
"Why does Helium give us high pitched voices." My question is,
if Helium gives us a higher voice because its less dense than
regular air, will inhaling a denser gas make our voices deeper?
Never have done the experiment, but it would be a reasonable
prediction. Of course, the choice of gases is very limited, based
on toxicity, lung irritation etc. In addition, the difference in
molecular weight of air (MW~ 30) and He (MW ~ 4) is a factor of 30/4
~ 7.5. A likely heavy gas candidate would be Xenon (MW = 131). Its
relative molecular weight (~131 / 30 ~ 4.4), so the "effect" may
only be about half as noticeable. And if the "physics" implies that
the relation of "pitch" and MW is the square root of the MW the
effect will be smaller yet. So it may not be so obvious as with He.
It is a matter of the speed of sound, which is a consequence of the
molecular weight of the gases used. The wavelengths of the sounds
making up your voice are determined by the geometry of your vocal
apparatus. The frequency, and hence pitch, of the sound is
determined by the wavelength and the speed: the faster the speed at
a given wavelength, the higher the frequency.
So, according to that simple model, inhaling a denser gas should
give a deeper voice. That is my prediction, which I have never
tested. One of these days, I need to find out for myself if it really is true.
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Update: June 2012