[TenTec] headphone alarmists

[Gary Hoffman]

True enough !

>From my old days as an acoustician, I vaguely remember the OSHA limits for
sound pressure levels on the db A scale.  They ran something like this,
although my recollection of the numbers may be slightly off, by a matter of
a few dBA.

80 dBA - unlimited time of exposure permitted.

85 dBA - up to 8 hours of continuous exposure permitted.

90 dBA - a short time permitted - I forget the exact number.

95 dBA - no exposure permitted without hearing protection.

110 dBA - threshold of pain.  Obvious damage.


Now you can see from this that there is a lot of leeway in the system.
Obviously, a short blast of say 90 dBA sound (lasting for as short a time as
it takes to grab the volume control) is not going to deafen you.  A blast of
110 dBA lasting milliseconds  (as in a gunshot) WILL damage your hearing
immediately.  A range of effects in between is possible.

Also, your ears recover with time, if you don't exceed the level and time of
exposure limits.  That is to say that, while listening to say, an hours
worth of really loud music at 88 dBA  (that's REALLY loud) may cause you to
experience a temporary hearing threshold level shift, it will not cause a
permanent threshold level shift.  That's why when you leave the rock concert
you can't hear worth a darn, but your hearing is Ok the next day.

On the other hand, a real 110 dBA blast will do you right now !

So, be careful, but its hard to do real harm unless you really abuse your
ears.  But - its not impossible.

73 de Gary, AA2IZ


----- Original Message ----- 
From: <hcawthra at sbcglobal.net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Thursday, December 29, 2005 9:23 PM
Subject: [TenTec] headphone alarmists


> Common sense, where has it gone!
>       73  Howard KA6IOB
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