David Clarke Reviews

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.

With DCs the passive attenuation is on par with other (non ANR) headsets.
The ANR is ADDITIONAL attenuation, with main benefits being increased
clarity of speech and less fatigue. They're really designed for aircraft
type noise levels (which in the big picture of things aren't really that
noisy inside) - they wouldn't be sufficient for such things as daily
chainsaw useage. If you need high frequency protection from relatively high
noise environments then an aviation type headset isn't the right tool for
the job.