eli5: Why are sped up voices so high?

Question

When watching videos/listening to audio that is sped up the voices are always higher than normal. Why is that?

In: 2

Answer 1

Sound is vibrations in air (or other materials). To our brains, more rapid vibrations are interpreted as a higher pitch. The lowest pitch we can hear corresponds to about 20 vibration cycles per second, while the highest pitch corresponds to about 20,000 cycles per second.

If you speed up a sound recording, you speed up all of the vibrations, making them higher pitched.