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In many films/television series/videogames, a character who has been reduced to minuscule size either by magic or advanced technology suddenly starts to speak with a very high-pitched, squeaky voice- has there ever been a reason stated for this?

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    It's probably just done to follow a trope most of the time. Practically speaking, pitch (frequency) has an associated wavelength in a given medium; a tuned apparatus for creating a sound in air will produce a certain frequency for a given length - longer for lower pitches, shorter for higher pitches. If an apparatus is shrunk down in size, it would make sense that it will generate sound at a higher pitch.
    – Anthony X
    Mar 6 at 22:38
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    Shorter and thinner vocal cords are associated with higher pitched voices in real life--this is a main reason children mostly have higher voices than adults, and women mostly have higher voices than men (see this article). We can also control the pitch of our voices to some degree, but that's done by using muscles that contract or stretch the vocal cords.
    – Hypnosifl
    Mar 6 at 23:25
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    Why all the votes to close? I thought it was a fair question.
    – Nu'Daq
    Mar 7 at 0:00
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    @DavidW- yeah but I wasn't talking about real world creatures now was I?
    – Nu'Daq
    Mar 7 at 2:57
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4 Answers 4

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In the real world smaller versions of things tend to make higher sounds than big things.

Think of :

  • a double bass vs a violin
  • a big drum vs a small drum
  • a big drill vs a small drill
  • the bong of a big bell vs the ting of a small bell.

The actual mechanical reasons why this happens may vary from object to object, but the common experience is that small things make higher sounds than large versions of the same thing.

It's really only logical to think that a person shrunk by magic or SF-handwavium would find their voice getting higher.

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    Technically the production of the sound is a function of the strings, not the body. The the body (soundboard) is sized to preferentially amplify the correct range of notes, but it doesn't produce them.
    – DavidW
    Mar 7 at 2:53
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    A better analogy would be with the strings of a piano or harp.
    – DavidW
    Mar 7 at 2:54
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    @Kevin I didn't say anything about drums or bells. What do drums or bells have to do with my comment? Strings are a decent analogy for vocal cords, and a piano (or harp) makes the relationship between length and pitch very clear.
    – DavidW
    Mar 7 at 4:15
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    @DavidW: The answer to which your comment is attached references both of those objects. If your comment is not a response to this answer, then it should perhaps be posted as a separate answer.
    – Kevin
    Mar 7 at 4:31
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    @Kevin Is there a stack overflow rule or guideline stating that a comment must address the entirety of an answer?
    – nasch
    Mar 7 at 17:13
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There's a bit of artistic license I'd say due to Pete's answer that we expect small things to sound higher pitched than big things.

But actually, the character has smaller vocal chords now, so they would likely vibrate at a higher frequency and therefore make a higher pitched sound.

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Providing the physics background to the other answers:

Sound is transmitted as a wave. The frequency of the sound generally corresponds to what we know as pitch. The frequency f is inversely related to the wave length λ via the speed of sound c, as in f = c/λ or λ = c/f. In other words, the higher the frequency (pitch) of a wave, the shorter your wave, or the longer the wave the lower your frequency.

Any noise is just swinging air molecules that reach your ear. Music instruments will vibrate (i.e. a swinging string or drumhead, a vibrating triangle, a "vibrating" air column in a flute). The lowest possible note will have the longest wave length and corresponds to the string length, air cavity etc.

As the other answers have pointed out, smaller people have smaller vocal chords, which are, grossly simplified, like a guitar or violin string. Thus they can not create as low notes as humans with regularly sized vocal chords.

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    +1 However, a technical niggle: "The frequency of the sound is what we know as pitch." This is technically false in quite a similar way that saying "frequency of light and color are the same thing" is false: frequency is a physical property, but pitch is a perceptual property, and the relationship between the two is complex. Psychoacoustics is weird and amazing. :) Also sound waves are longitudinal waves, not transverse waves, so "swinging" is not quite apt.
    – Lexible
    Mar 8 at 22:29
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just physics.

long vocal cord means long wavelength means low frequency, short vocal cord means short wavelength means high frequency.

Its is the same reason for that small speakers like in the smartphone are not able to produce good bass.

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  • Well, it's also the mass, and the length of the vocal cavity, but both of those scale as the length of the vocal cords.
    – DavidW
    Mar 8 at 18:09
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    Can you give an example when mass changes oscillation frequency? Consider the experiment in school where you have a pendulum. Its frequency is only dependent of its length, but not of its mass.
    – codymanix
    Mar 8 at 18:29
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    It's not oscillation frequency, IIRC, it's about resonant frequencies.
    – DavidW
    Mar 8 at 18:48
  • @DavidW Right, although resonant frequencies affect the timbre rather than the fundamental frequency itself in vocal acoustics.
    – user45266
    Mar 10 at 3:21

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