Science Questions

Why does my voice sound different on a tape recorder/microphone?

Sun, 10th Jun 2007

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Question

Cattom (via email) asked:

I'm from Singapore and I love your show.

I have a question. Why does my voice sound different on a tape recorder/microphone?

Answer

Thereís nothing worse than hearing a recording of your voice for the first time!  The reason is that how we think we sound isnít really how we sound.

Inside your ears there is an organ called a cochlea, a special neurological structure that converts the vibrations of sounds in the air into electrical signals that the brain can understand.  It gets stimulated by the pressure waves caused by sounds in the air, but at the same time can pick up the vibration of the bones in your skull.  When you are listening to sounds in the environment, the chief source of those sounds is coming through the air, very little comes through the bone.  When youíre speaking, however, your whole head resonates; it vibrates.  This means that your cochlea gets stimulated by your skull vibrating, as well as the sound coming out of your mouth and going through the air to your ears.

The body does two things; it gets a different version of those vibrations (through the bone and the ear), but it also has a protective mechanism to cut down the amount of sound which is going into the cochlea.  It reduces sensitivity of your ear a little when youíre speaking, so you get a slightly different rendition of what your voice sounds like.

Thatís why, when you hear yourself recorded and played back, you sound totally different, because all you hear back from the tape recorder is sound coming through the air, minus the skull vibration and bone conduction.

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