What happens when you inhale helium and then play a trumpet?

Question

We all know the silly effect that inhaling helium has on speaking and singing, where some wacky speed-of-sound physics makes our voices sound unnaturally and ridiculously high-pitched. A student asked me today what would happen if the same thing was tried blowing into a trumpet. What would the result be?

I was not comfortable instructing kids to try it out, as I'm sure deliberately inhaling helium must violate some sort of school safety rule. But it could make an interesting special effect and I'm intensely curious. Has anyone actually tried it?

Answer 1

OK, I'll do your Googling for you :-)

(There's one for trumpet too, but I thought a Helium Tuba might be even more fun.)

In the video, a tuba player uses a modified mouthpiece to inject helium into his mouth while playing. On a sustained note, the pitch rises by nearly an octave while the helium is being injected; once the helium is no longer being injected, the pitch slowly falls back to the expected pitch over the course of a few seconds. Melodies become quite difficult to play since the resonances of the instrument are constantly changing, and the player even has some difficulty with scales.

Answer 2

In addition to Laurence's answer: it's worth to note that the reason why the pitch of a wind instrument changes is different from why the voice sounds differently with helium.

In a wind instrument the source of sound is a vibrating air column, and the frequency is proportional to the speed of sound, see https://en.wikipedia.org/wiki/Acoustic_resonance#Resonance_of_a_tube_of_air . As the speed of sound in Helium is almost 3 times larger than in air, in pure helium the pitch would be almost an octave and a fifth higher than in air.

On the contrary, in human voice the source of the sound are vibrating vocal folds, and their vibration frequency doesn't depend on the gas medium. However the wavelength in helium does change, and it affects how various frequencies interact with your throat and mouth resulting in a different timbre. See this question for more detailed explanations: https://physics.stackexchange.com/questions/122353/why-does-our-voice-sound-different-on-inhaling-helium

Finally, while helium itself is harmless, there are indeed safety considerations when breathing it, especially from a pressurized container, including risk of asphyxiation, mechanical damage and others, see e.g. https://www.healthline.com/health/inhaling-helium . Insides of balloons are often coated with talcum powder which (in large amounts/regular exposure) can cause lung issues.