Industrial Deafness vs Tinnitus (was Re: OT: Power Supplies)

[Alex Satrapa]

On Thursday, September 19, 2002, at 04:53 , Antti.Roppola at brs.gov.au 
wrote:

> Will low level white noise do that? I thought it was the sound
> pressure that damaged the cilia.

Cumulative power can do it too.

> Industrial deafness (tinnutus) gets you a ringing in the ears rather
> than silence.

Industrial deafness != tinnitus.

In industrial deafness (which is commonly found in earthmoving workers 
and rock music fans) is caused by the cilia being broken or calcified 
due to extensive damage.  When you suffer from industrial deafness, you 
have large portions of audio bandwidth perception missing - for example, 
you might not be able to hear sounds between 100Hz-200Hz.  When you play 
a continually rising pitch at a constant volume, some people with ID 
will perceive it as dipping slightly in volume, disappearing, then 
returning and rising in volume again.  Others will simply perceive the 
sound as disappearing entirely.

One theory for a possible cause of Tinnitus is that it's caused by cilia 
becoming entangled or the auditory nerves becoming damaged - thus 
leading to a constant signal to the brain saying "we can hear this 
frequency".  You can still hear those frequencies when they are present, 
but you can hear them when there are no external sources too.

I suffer from a very mild case of Tinnitus - everywhere I go, I have the 
high-pitched whine of a TV or computer monitor in my head.  I'm very 
sensitive to the noise of CRTs and some hard drives as a result (I can 
perceive the noise at levels other people claim are inaudible).  I like 
KMFDM because a lot of their music has a "wall" of sound - practically 
every frequency is used.  This helps to mask the tinnitus in a similar 
way to "therapeutic noise generators" (pink noise sources).

Tinnitus and Industrial Deafness can be caused by the same thing - 
excessively loud noise.  Industrial Deafness can also be caused by 
environmental noise - for example a vacuum cleaner running for 4 hours 
can cause problems.  I expect a loud hard drive or power supply fan that 
is in your presence for 12 hours at a time would be just as bad.

Then there is selective perception - where no physical damage is being 
caused, it's just that your brain has accepted that particular noises 
are a normal part of the environment.  When the noise disappears, you 
will experience a sense of loss because your brain is trying to 
compensate for a noise that doesn't exist.  Doesn't matter whether the 
noise is a fan that has stopped blowing or a baby that's stopped 
crying - your brain wants you to be in panic mode :)

However, I would play it safe.  Don't have the noise around if you can 
avoid it.  Don't mask the noise - eliminate it.

Alex

PS: You might be able to find something of interest about tinnitus here: 
http://www.tinnitus.asn.au/tinnitus.htm - the emphasis being that we 
don't know what causes tinnitus, but we do have lots of theories that 
make sense.
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