Why does our voice sound deeper when we slow-mo but sound more high-pitched when we fast forward?

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Why does our voice sound deeper when we slow-mo but sound more high-pitched when we fast forward?

In: Physics

Sound is a vibration. When you slow the speed of a recording, you slow the speed of the vibrations in it, which lowers the pitch. When you speed it up, you speed up those vibrations so it sounds higher pitched.

Think about it this way: Al has a really deep voice, and when he says “Wow.” his vocal cords vibrate 1000 times and it takes one second. Barb has a high-pitched voice, and when she says “Wow” her cords vibrate 2000 times over the course of a second. Now if you record them both, and speed the playback of Al’s Wow to double speed, then his voice vibrates 1000 times in a half second, which is the same rate of vibration as Barbara’s voice. So it should have about the same pitch.

Because that’s how sound works.

Sound is a wave that travels through a medium i.e a substance, object. It travels by pushing the atoms back and forth. Your ear has a drum that moves forward and backward when air around it moves back and forth then this motion is transferred to a couple of bones and special sensors and then your brain which registers it as hearing. Sound waves, as every wave, has some differentiating properties. Like how far, harsh they push the atoms. This is the amplitude of the sound wave. We hear it as the loudness of it. The another property is how often they do it so. This is the frequency of a wave. We hear this as the pitch.

If something vibrates air slowly, then you hear a low-pitched i.e. deep sound. If something vibrates the air fast then you hear a high-pitched sound.

By slowing down a recording you increase the amount of time that the recorded sound to be created which decreases the frequency of the actual sound. You hear this new sound wave as a deeper sound.

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