

Sonic Boom: How digital technology is transforming our relationship with sound - sizzle
http://www.theatlantic.com/features/archive/2014/05/sonic-boom/361483/

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Anechoic
_This is, not coincidentally, just under the 85 decibels or so that can, over
long periods of exposure, compromise the delicate infrastructure of the human
ear._

There is a presumption that is commonly made in many circles (including this
article) that because NIOSH noise exposure limit is 85 dBA over eight hours,
that it's levels at 85 dBA or over that cause hearing damage. Hearing damage
can actually start at 75 dBA for a small segment of the population and at 80
dBA for most people over the long-term (about 10 years) [0],[1].

The 85 dBA NIOSH number (and the 90-dBA OSHA number) represent a compromise
between an "acceptable" (my words) amount of hearing loss and the costs for
businesses to implement effective noise control measures to reduce noise. The
acceptable amount of hearing loss is based around workers' ability to
understand human speech, and it assumes that hearing loss above 4 kHz "must be
accepted as part of the jon." Those limits also assume that workers' are only
exposed to high noise levels during their work periods - if Sam works 40 hours
at 84 dBA per day and then attends a rock concert on the weekend, he exceeds
his allowable noise dose.

I don't mean to write this to be nitpick, I just want to underscore that if
you really care about your hearing, you really need to avoid levels above 80
dBA as much as possible over the long-term. However avoiding high noise levels
is very difficult to do so (especially if you live in a large city) and for
many of us it's way to late.

For those of you in the Boston area, the Greater Boston Chapter of the
Acoustical Society of America holds monthly meetings where presenters discuss
and demonstrate many of the issues discussed in this article - everyone is
welcome (especially students) and the meetings are usually held at Acentech's
Cambridge office so you can meet some of the folks in this article. The GBC-
ASA website is at [http://www.gbcasa.org](http://www.gbcasa.org).
Unfortunately it's undergoing a takeover from national ASA so there is nothing
there at the moment, but I expect content to appear again shortly. There is
also the @GBC_ASA twitter account for announcements.

[0] Fundamentals of Acoustics, Kinsler et al, Chapter 13

[1] Keep in mind these are A-weighted decibels, linear decibel levels will be
different

