I'm an engineer working at the Communications Research Centre Canada in Ottawa,
Canada
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my name is mark T... i'm 9 years old. i'm doing a report for school and would like to know why helium makes your voice sound funny. i'm in grade 3 at north calgary christian academy in calgary alberta. i would like if you could send an answer back to me. my address is ... calgary alberta ...
thank you
mark T...
Hang on to your hat! I will try to make it as simple as I can.
Your voice sounds the way it does because of the size of your head and the size of your vocal chords (or voice box) at the back of your throat. Grown-ups sound different partly because their heads are bigger. Sound takes longer to travel from the vocal chords to the lips in a grown-up.
Air is made up mostly of oxygen and nitrogen gas. Oxygen and nitrogen are heavier than helium. That is why helium balloons float.
Now, when sound travels through air, it is like waves traveling on water and each wave has to push the air back and forth as it moves along. Because helium is such a light gas, sound waves traveling through helium don't have as much to push so they travel faster, in fact four times as fast!
So, if you are breathing helium, sound arrives at your lips four times as fast as it normally would. Actually it is exactly the same as if your head was four times smaller! Helium speech is often called "Donald Duck" speech because it sounds like a duck talking. That is why it sounds funny.
Working for the Canadian Navy, divers go very deep in the water and the pressure is enormous. They breathe air at high pressure too, and ordinary air becomes dangerous to breathe. It can cause "the bends" and "rapture of the deep".
So they breathe a mixture of helium and oxygen instead. But you can't understand what they say, so we developed a little box that electrically "magnifies the head" so to speak, and makes what they say understandable again.
I hope this helps! I am sending this explanation back with a cassette that contains a bit of helium speech before and after descrambling. Maybe you can play it for your class.
Sincerely Yours,