Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: Aaron Carr on 04/06/2008 10:47:56
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Aaron Carr asked the Naked Scientists:
Hey guys, probs and obvious question...
Just wondering, say you crashed your car and you were left passed out with
your head on the steering wheel. Would the constant noise from the steering wheel horn affect your hearing, even though you are passed out and not actually hearing it?
Cheers, Aaron from Canberra, Australia.
What do you think?
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I doubt a car horn would be loud enough to cause any permanent hearing loss unless your head and ear was pressed up against the sound generator itself.
You hear sound when an object moves or vibrates,these vibrations are passed on to the air molecules around us and in turn travel to our ears where they hit our eardum which then passes the vibrations on to tiny little hairs inside our ears . As these hairs vibrate they turn the vibration into an electrical signal which travels to our brain.
To loud a sound and the tiny hairs can get damaged and knocked down, if they cant repair themselves there ability to feel sound vibrations is reduced which then reduces our ability to hear.
This process continues even if we our asleep and the only effect of being unconscious would be the inability to turn our heads or cover our ears to limit the level of sound.
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There is an autonomic mechanism to protect the inner ear from loud sound called the "acoustic reflex",
it is analogous to pupil constriction reducing the light entering the eye, [or AGC in an electronic device].
The vocalization-induced stapedius reflex can indeed be used for hearing protection purposes. Just before an impulse noise (door slam, electromagnet lock slapback, gun shot, pound of hammer on nail) one could vocalize (or cough or hum) to protect one's hearing from the sound pressure that the impending sound would create. The reflex is not a perceptual reduction in sound; the reflex is a real reduction in sound level reaching the inner ear — an actual reduction in how far one's delicate hair cells will be bent by that sound. An identical hammer blow when one engaged in no vocalization is more damaging to one's hearing than that same hammer blow if one began vocalizing just a few tens of milliseconds prior to the blow.
http://en.wikipedia.org/wiki/Acoustic_reflex
So the seven dwarfs advice to “whistle while you work” was correct, although the line “it’ll prevent hearing loss” was omitted. [:)]
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yes ofcourse, actually tympanic membrane vibrates with the sound waves and it also occurs even when the person is unconscious just the perception is lost. so in cases like fire explosion and when typmanic membrane is damaged , there will be the same level of damage in the unconscious person too.