Science Questions

Why does my voice sound different in my head?

Sun, 23rd Sep 2012

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Question

Lisa Valleroy-Djang asked:

To whom this may concern:

 

Sorry to continue trolling you with questions, but I was wondering why my voice always sounds so different on a recorded device then how I think I sound. Everyone seems to have that experience where they think "do I really sound like that?" Do we hear are own voices differently that how we sound to others?

 

I hope this makes sense.

 

Science on,

 

Lisa

 

 

 

Answer

Chris -   The reason is quite simple really.  What you have when you have sound coming in to your ears, when I'm listening to someone else speaking to me, I'm just getting sound vibrations in the air coming through the air.  They go into my ear canal, the bit you can stick your fingers in on either side of your head.  They hit your ear drum and the ear drum is a flat sheet of tissue which when the air vibrations hit it, it makes the ear drum vibrate in sympathy with the vibrations in the air.

Those vibrations are then transmitted via a series of 3 tiny bones into what's called the cochlea.  The cochlea is the inner ear and in there is a structure which has a long membrane which is fat at one end and thin at the other.  Because its thickness changes, its stiffness changes along its length and this means that some bits of it resonate at some frequencies and other bits resonate at other frequencies.  And sticking into it are structures called hair cells and these hair cells will be vibrated more or less according to which bits of that structure are vibrating.  And the vibrations transmitted into the hair cells make the hair cells become electrically active and when the cells are electrically active, they fire off impulses into what's called the auditory nerve.  That then sends a signal down into the brain stem and then it gets projected onto the part of the brain that decodes your ability to hear.  

So, when you are listening to sounds coming from outside, thatís what's happening, but when you're actually making sounds yourself, in other words, your vocal cords are opening and closing and creating puffs of air that themselves create resonances inside your throat and your mouth.  Some of those resonances are going to be transmitted into the bones of your head and your skull.  The bones will conduct the sound also to the cochlea, so the cochlea will also get sounds from inside your head.

So when you speak, you hear both the sound coming through the air and you also hear the sound of your bones vibrating.  And that is why, when you speak yourself, you think you sound different to what you sound like when people play something back if having recorded you earlier, because what you're actually hearing is the two sounds superimposed.  When you hear the recording made outside your head, thatís the pure sound of what you really sound like and yup!  Believe you me, itís pretty painful to listen to because itís very much a sort of self-conscious thing.  GinnyÖ

Ginny -   One of the other Ig Nobel Prizes, we spoke to one of the Ig Nobel Prize winners earlier, were actually a pair of Japanese scientists (inventors really) who invented the device they called the speech jammer which actually played your own voice back at you at just a few milliseconds delay, I believe, and itís so disrupting to hear your own voice back with that slight delay that it basically shuts people up if they're talking too much.

 

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When we speak, part of the sound we hear comes from the sound of our voices reaching our ears, but part of it is also internal resonances through our skull, which can stimulate the cochlea directly, and this changes the frequency response slightly.

There is also some resonance in our ear canal. You can get an idea of this if you block your ears and speak, although the effect is exaggerated by the blocking of the ear canal.

This becomes a problem when we fit hearing aids because if someone has good low-frequency hearing, blocking their ear canal with a mould makes their own voice intolerable to them. It's called the occlusion effect. http://en.wikipedia.org/wiki/Occlusion_effect

That's why I'm always disappointed to find out that my voice isn't manly and full of dulcet tones, but rather whiny and nasally and horrible! bizerl, Thu, 19th Jul 2012

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