Teacherjh wrote:


There is some question of the value of ENR (Electronic Noise Reduction)
in avoiding future hearing loss. Our company investigated supplying ENR
headsets in a high noise area, but decided not to, since there was no
demonstrated value. In short, ENR only works on lower frequencies, and
those frequencies typically don't affect hearing as much as higher
frequencies.


... and smoking hasn't been proven to cause cancer.

If you put them on, and it seems quieter (vs a non ENR set) then it's probable
that there is less noise entering the ear. This probably leads to less damage
(if we accept the premise that noise at that level causes damage).

Perhaps. The general consensus is that A weighted noise is what causes
hearing damage. That weighting scale drops off below about 1000 hz,
meaning that people don't readily hear low frequency noise. People tend
to feel low frequency noise more than hear it. The ENR systems
typically only work in those low frequency ranges, which is why it is
felt they have limited value in avoiding hearing loss, except in
extremely noisy, low frequency environments.

To put it in perspective, note that a two-bladed prop rotating at 2,000
RPM, will generate a noise frequency that is about four times the
maximum rate that the ENR systems work at.

I find ENR works on the higher frequencies too. I put on my DCs passively and
can still talk to people around me. I flip on the ENR and it's like I've gone
deaf.

It actually doesn't work at higher frequencies. If you read the
specifications for those systems, you will find that they typically
don't attenuate noise above about 500 or at max 1,000 Hz, which are both
low frequencies. The reason is that there is a risk of compounding
noise, instead of attenuating it, as the frequencies increase. What you
are finding with the ENR system is that it reduces the low frequency
noise and allows other sounds to come through more clearly.