Non Life Sciences > Physics, Astronomy & Cosmology

Why does Helium make my voice pitch change ?

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daveshorts:
I think the link Chris wanted was:
http://www.phys.unsw.edu.au/PHYSICS_!/SPEECH_HELIUM/speech.html

I think it basically says that your voice system consists of two parts your vocal chords/folds and your throat. It is a bit like a very short trombone, the vocal chords are like your lips in a trombone and the throat like the tube.

 The vocal chords vibrate produce lots of harmonics f,2f,3f etc. (where f is the lowest frequency you produce)  setting the base frequencies of the voice.
Your throat is a resonator, so it will vibrate better at some frequencies than others, so it will affect the  relative strength of each of the harmonics.
eg if you make your mouth longer when you are humming it will make the lower harmonics stronger and the higer ones weaker sounding deeper. The relative strength of these harmonics are called the timbre.

Because the speed of sound is much faster in helium it is like halving the length of your throat (but less painful). The high harmonics are strengthened and the low ones weakened, so your voice sounds higher, without actually changing the frequency of your vocal chords.

Dave

ps It also has the perculiar effect of giving me an ozzie accent... I am not sure why
 

anthony:
My first post!

When I assisted in the training of ambulance technicians, and during training for myself, I took a few puffs of Entenox, nitrous oxide and oxygen mix, 50/50. The tone of my voice went down. The mixture is more dense than air, so agrees with many of the suggestions proposed so far. You could try the experiment for yourself, though perhaps best to avoid controlled medicines, try argon, the same as you would a helium balloon.

I was going to post a suggestion, but then I realised that Daveshorts gives an explanation I can't find fault with.

chris:
I'm a bit worried about Anthony's suggestion to try breathing argon to see what sort of effect it might have on voice timbre. Argon, being so much heavier than air, is likely to sit at the bottom of the lungs, displacing the light gases (e.g oxygen) upwards.

I suspect this might have a deleterious effect on consciousness...

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

bostjan:
The speed of sound/frequency explaination is incorrect, because the wavelength of the sound changes through various media, whilst the frequency remains the same.  Otherwise, you would only hear very high frequencies when you hold your ear up to a wall to hear what was on the other side, because sound travels faster through a wall than through air.

The timbre certainly does change.  This is why you sound more like a duck than like a mouse.

syhprum:
The 'Helium' sold for inflating balloons is a mixture of Helium and Nitrogen to reduce the cost as the full lifting potential of pure helium is not needed for toy balloons.
If you measure the actual change in pitch you will find it much less than that which deep divers produce on the genuine article

syhprum

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