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Klarinet Archive - Posting 000349.txt from 2001/05

From: Bilwright@-----.net (William Wright)
Subj: [kl] ...more about sensitivity & decibels
Date: Sat, 12 May 2001 21:46:31 -0400

Despite the one-liner about my daighetr cleaning her room, I wasn't
jesting that she has hypersensitive hearing, nor about "turning nerves
off". She has been tested by audiologists and counselled on how to
cope, etc.

Therefore last night was astonishing to me, and it also made me
angry:

I haven't chaperoned (or attended) a teen-age dance for 20-30 years
now. I had no idea what occurs nowadays when a "DJ" plays canned music
at these things. The barrage of sound was so fierce that I was unable
to remain inside the building and carry out my chaperone duties.
Mercifully they shifted me to 'outdoors sentry' instead.

I knew that my daughter couldn't handle that much noise, and so I
suggested that I take her home and then I would return to perform my
sentry duty. To my absolute astonishment, she told me, "No problem,
this isn't loud."

If ever there was an example of how a musician might 'feel' tone
through a clarinet's holes (see below about misinterpreting bone
conduction) and yet not feel excruciating pain while doing household
chores, this was certainly it. Somehow my daughter managed to "turn
off" an entire neural pathway.

Why was I angry? Because after a couple of minutes, I 'woke up'
and realized the potential for hearing damage to my daughter and to all
the other children. I was not alone in this. Several other adults
had the same complaint, and the teachers agreed and they forced the DJ
to turn the volume down a bit.
But afterwards, I was *still* unable to remain in the building for
more than 30 seconds or so. At this point, other adults were shrugging
their shoulders and saying "It's OK now, the kids think it's cool."

I happen to have a decibel meter with a few extra functions
(A-scale, C-scale, adjustable sample period, peak vs. weighted average,
etc). So I went home and got it. The gentlest 'song' that I tested
was 102 dbA. The loudest song was 109 dbA. These readings were in
the dance area, not standing directly in front of one of the large
speakers. The lowest reading that I could obtain was 92 dbA if I stood
in the doorway that was the main entrance to the building (cafeteria,
actually).
My meter is not a laboratory instrument, but on one occasion I used
it side-by-side with a professionally calibrated meter in the
$10,000-$20,000 range operated by a certified technician. The readings
were similar enough for estimating dbA levels.

I'm not a physician, but most audiologists say that the risk of
permanent hearing damage begins at 85 dbA of repeated extended
exposures. A web page from NIH (National Institute of Health) talks
about risk of permanent hearing damage after 60 seconds of exposure to
110 dbA or after 15 minutes at 100 dbA.

....and these readings were taken _AFTER_ the DJ turned it down
enough that I and other adults could notice a reduction.

A few months ago, this list discussed orchestra members wearing
earplugs. I should search the archives to see if any of those posts
mention specific decibel readings.

The question of what I'm going to do about this incident isn't
relevant to the Klarinet list's conversation, but it does provide an
excellent real-life example of how much ability the human nervous system
has to turn its perceptions "on" or "off" --- although I don't know
enough physiology to know how sensitive a fingertip is under laboratory
conditions, nor whether a musician may report feeling tone via the
fingers even though the sensation actually arrived through bone
conduction in the head area.

......and also BTW, my ears were still ringing and my hearing was
still noticeably (to my perception) duller than normal when I practiced
10 hours later. It's been 22 hours now, and most of the effect appears
to have disappeared..... I hope..... it's all very subjective.

Cheers,
Bill

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