James Robinson wrote:

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.

ANR can be designed to work on any frequency. I suggest your company might want to
check out the Bose ANR headphones (nonaviation). They seem to block out all
frequencies. Great hearing protectors in a noisy environment.

George Patterson
This marriage is off to a shaky start. The groom just asked the band to
play "Your cheatin' heart", and the bride just requested "Don't come home
a'drinkin' with lovin' on your mind".