[Marxism] RE: Noise and worker's hearts

Les Schaffer schaffer at optonline.net
Sun Nov 27 14:17:40 MST 2005


it appears our "intelligent designer's" work is unfinished.

the ear is an amazingly sensitive organ, it enables us to hear sounds 
over many many orders of magnitude in loudness. vibrations of surfaces 
on the order of atomic dimensions can be detected by the ear. i used to 
think the eye was tops, now i know the ear is as amazing.

being ourselves fluid on the inside surrounded by an ocean of air, 
hearing organs evolved mechanisms for coupling the sound presure waves 
in air effectively to the fluid in the inner ear, via three of the 
smallest bones in our body. it is this exquisite impedance matching 
device that gives us such sensitivity. without the impedance matching, 
sound waves in air would mostly reflect back from a fluid-filled inner ear.

within the inner ear sit of order 20,000 hair cells, which respond to 
induced wave motions in the fluid and convert them to electrical signals 
destined for the brain. and it is here that hearing loss takes place. 
prolonged exposure to loud noise can damage these hair cells, usually 
permanently. someone correct me if i am wrong, but this exposure need 
not be accompanied by physical pain, as in  damage to the eardrum.

as Rossing points out in "The Science of Sound", we developed eyelids 
for good reasons, amongst them we developed always in a sunlit 
environment. Rossing points out that only in the industrial age did 
humans (errr, a class of them) need to co-exist with loud machinery. 
hence the comment on our dear intelligent designer, and his forgetting 
to install earlids. there is also a muscular based response that can 
limit the sensitivity of the ear by about 20 dB, but it is not fast 
enough for gunshots and other short period bursts.

tractors: the latest reference i could find was a 1989 study of 
teenagers on farm. i will keep looking. i drove tractor in the summers 
for several years, but always used ear muffs.

rock concerts: my understanding is that the occasional concert induces 
only temporary damage. musicians constantly on tour, however, can 
experience permanent hearing loss. think levels times length of exposure.

les schaffer

p.s. inner ear via hair cells and fluid is also responsible for 
maintaining sense of balance.




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