Dense Gas and Pitch Name: Jhon Status: student Grade: 9-12 Location: CO Country: N/A Date: July 2006 Question: 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? Replies: 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. Vince Calder 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. Richard Barrans Click here to return to the General Topics Archives

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