It's common knowledge that helium can change its sound, but how does it change its sound?

When the person speaks, the sound that the vocal cord vibrates gives out itself is not big, rely on the resonance action of oral cavity just magnify. The voices we hear from others are amplified by resonance. Helium, or helium, travels faster than air, so it has a higher resonance frequency than air.

For example, when speaking in normal air, the resonance frequency of the mouth is low, and the medium frequency components in his voice are amplified, while the higher frequency components are not amplified, so the voice is normal. When he inhaled the helium, the resonance frequency of his mouth increased, and while the vocal cords vibrated in the same way as usual, the higher-frequency components of his voice were amplified, and the middle-frequency components were not, so he sounded much higher than usual.

In short, the frequency of the words doesn't change with or without helium. It's just that the helium changes the resonance frequency of the mouth, increasing the high frequencies in the voice and weakening the middle and low frequencies, which the listener perceives as being higher in pitch.

Specific method, direct inhalation can be. However, although helium (high purity helium) is an inert gas with no direct toxic effects on the body, do not inhale more, in case it disrupts normal breathing to carry oxygen.