Thursday, November 12, 2009

Re: the phrase 'setting my teeth on edge' why does the scratch of a nail on glass causes a teeth sensation?

In the days of old-fashioned blackboards a little impurity in chalk screeching on the board would cause nearly all kids to cringe. Why is the sensation felt in the area of the teeth (particularly upper teeth)?

Re: the phrase 'setting my teeth on edge' why does the scratch of a nail on glass causes a teeth sensation?
It's due to the frequency of the sound. It sets up a resonance from the cochlea and is transmitted through the nerves into the teeth.
Reply:It doesn't, but I mourn the passing of the blackboard. Just to make the gesture would subdue the most unruly class.
Reply:I don't know but cardboard and toilet tissue has this effect on me.
Reply:maybe your teeth relate to the noise as it's similar to grinding your teeth - so your teeth 'feel' the pain of the blackboard?
Reply:It could be a "referred" sensation (e.g. like feeling sensation in a missing limb, as was often reported by soldiers after WWI %26amp; II).


The brain associates the sound to a physical sensation and "expects" to receive nerve impulses from the teeth.





The question then is, whether or not the body responds sympathetically by activating nerves in the teeth. It is often said that when the (unconscious) brain "imagines" pain, it is as real as the pain itself.
Reply:It is the effect of the sound wave at that frequency. Younger people are more sensitive to higher frequencies and so more likely to cringe at squeaky noises than teacher. Your upper jawbone is connected to your skull near the ear, and so picks up the more extreme sound waves.





Believe it or not, the police in Manchester are now experimenting with broadcasting very high pitched noise to disperse gangs of youths - the pitch is too high to affect most adults but apparently excruciating to teenagers. Sounds a bit sinister to me....


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