• Question: when you suck in helium, why does your voice become squeaky?

    Asked by mcloughlinlwh to Helen, Jenni, Mark, Martin, Stu on 22 Jun 2011. This question was also asked by tompkinshwh.
    • Photo: Jenni Tilley

      Jenni Tilley answered on 20 Jun 2011:

      Because sounds travels faster (higher frequency) in helium than in air and pitch (height of note) is directly related to wave frequency. So when you surround your vocal chords with helium, the sound waves travel faster (higher frequency) resulting in a higher pitch. Other gases slow down the sound waves and your voice sounds lower.

      This is related to why a police car siren sounds higher when the car is coming towards you and lower when it’s moving away from you. As the car moves towards you, the sound waves ‘bunch up’ like a compressed slinky, making the wavelength shorter (and so frequency higher). As it travels away from you, the waves get stretched out like an extended slinky, so the wavelength is longer and the frequency is lower. This idea is called the Doppler Effect, and astronomers use it to measure how far away stars and galaxies are!
      http://en.wikipedia.org/wiki/Doppler_effect

    • Photo: Helen O'Connor

      Helen O'Connor answered on 22 Jun 2011:

      Helium is lighter than air so the speed of sound is much higher in helium and when you inhale helium you increase the speed of the sound of your voice.

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