On Wed, 14 Jun 2006 09:32:23 +0200, Thomas Borchert
wrote:

RK,

The question is, does ANR do any better at attenuating the
ear-damaging frequencies than ordinary noise attenuating headsets?


I suggest you read the ANR tutorial at Lightspeed's website.

I did read that article, as suggested by Marc J. Zeitlin in a previous
message in this thread, thank you both. While an interesting article,
it doesn't really tell me too much that I didn't already know, or
suspect, and it doesn't constitute the scientific evidence that I'm
looking for.

I did a search in Google Scholar for papers on the subject and hit a
paper that appeared in "Journal of Occupational Health" reporting a
study on an ANR (or ANC) for industrial workers. That article
presented evidence that workers showed less TTS (Temporary Threshold
Shift), as measured with an audiometer, when using ANC hearing
protection. TTS is apparently that "dullness" in your ears that you
feel after a bare-eared flight. While the study doesn't cover aviation
headsets, it does suggest that ANR might be more effective at
preventing hearing loss than conventional noise-attenuating headsets,
which in turn are better than nothing at all. The article reports
p0.045 using the Wilcoxon sign rank test. Now that's the kind of
statistical evidence that I can get my teeth into. Give me some reason
to accept or reject h0. Does anyone know of scientific papers or
journal articles on Aviation ANRs? Preferably a paper that I can
download as a PDF for free instead of having to pay a fortune to buy a
copy from one of those scientific paper publishers.

Of course I've always been concerned about hearing loss as I already
have a hearing loss in one ear (mumps when I was 5) that kept me from
pursuing a commercial license (though recent rule changes could change
that). Consequently, I've always been interested in keeping what I
already have and was rather excited when I first heard that Bose was
introducing an ANR headset--until I found out that I couldn't afford
it. I do fly a somewhat quieter airplane, a Cherokee, so it's not as
bad as with some airplanes. I once used a sound level meter and found
that the noise in the Cherokee was only a few db higher than my car (a
Vega at the time) though with the logarithmic db scale, only a few
points still means an awful lot of noise.

I may be ready for a new headset since I've been noticing that my
current headset, a cheap DC knock off, has lately been exhibiting
audio dropouts. I suspect a broken wire in the plug. Now if I could
only come up with the cash. After the disastrous annual inspection
this year and the recent slide in the stock market, I'm not prepared
for a headset. Maybe if I bought a lottery ticket every day...

RK Henry