Wayne.Roorda@p0.f14.n385.z1.fidonet.org (Wayne Roorda) (12/21/90)
Index Number: 12540
[This is from the Silent Talk Conference]
In the November 1989 issue of DISCOVER Magazine, in the Up Front
section on page 18 there is a column titled "Bad Vibes".
Hearing specialists have long stressed the dangers of rock concerts,
but it's not the moral fiber of America's youth they're worried about.
What concerns them are the fine, upstanding tufts of hair that stick
up from the sensory cells of the inner ear. When exposed to
prolonged, intense sound, these hairs can flop over like stalks of
wheat pummeled by hail. Until recently, however, no one knew exactly
why they collapsed.
Using an electron microscope, Harvard physiologist Charles Liberman
examined the sensory hairs of cats that had sustained mild but
potentially reversible hearing loss, then compared them with the
sensory hairs of cats with permanent hearing loss. "With temporary
loss, you can't see a heck of a lot wrong with the hair cells,"
Liberman says. But in the permanently deaf cats the hairs had keeled
over. The hairs' rootlets - the small, narrow structures connecting
them to the rest of the cell - were broken.
Liberman thinks of the damage to the rootlets much like a stress
fracture. When sounds enters the ear, he explains, the hairs rock
back and forth in response to the resultant vibrations. The rocking
causes the sensory cells to release a neurotransmitter that stimulates
auditory nerves, leading to the sensation of sound in the brain. The
hairs themselves, however, are ridgid; they can bend only at the
flexible rootlet. If the rootlet is overstressed, forced to rock too
hard and too long, it can eventually break. With the collapse of the
sensory hairs, the whole cell becomes useless, as does its associated
nerve, and some hearing is lost forever.
"From a mechanical point of view, it makes intuitive sense that this
pivotal point is the weak link," says Liberman. And, although there's
no proof yet, he has a theory for why that link finally snaps.
"Constant rocking takes energy," he says. Moreover, it causes wear
and tear on the rootlet, and repairs take energy, too. "If the
intense motion goes on for too long," Liberman speculates, "maybe the
cell simply runs out of gas."
I copied this in hopes that we will get some feedback and or
discussion started from the hearing healthcare professionals and
"Silent Reader's" who may be reading this conference and not
posting. And everyone else let's hear from you too. BTW I've
cross-posted this to the ABLED echo too.
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Uucp: ..!{decvax,oliveb}!bunker!hcap!hnews!385!14.0!Wayne.Roorda
Internet: Wayne.Roorda@p0.f14.n385.z1.fidonet.orgAnn.Parsons@f207.n260.z1.fidonet.org (Ann Parsons) (01/09/91)
Index Number: 12714
[This is from the Silent Talk Conference]
Hi Wayne,
Well, this article comes at the most opportune time. I had a little experience
the other day. I was walking down a hallway in one of our local schools. Ahead
of me I heard the ninininininini noise of a walkman turned up so loud that I
could hear the sound through the earphones ten feet away. I ran up behind the
student and found him standing by a wall. I confronted him.
"Do you want to be deaf in twenty years?" I said. "Do you want to have to
learn sign language?"
I hate to say it but I went on for about a minute. I finally ran down and he
said, "Oh, yes, I know." He turned off the walkman.
Does anybody know how damaging these walkmans are? Has there been a study done
about that? I know about the loud rock music from speakers, but what about
earphones and walkmans? I found your article to be most interesting. If you
find anything more, please let me know.
See you on-line.
Ann P.
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Internet: Ann.Parsons@f207.n260.z1.fidonet.org