Morning all,

Our organisation has a small aerial survey team who fly at circa 4000ft taking aerial images of the land and sea. They are using twin engine light aircraft.

I need some support on the use of ANR headsets. The organisation make a large investment in ANR headsets for crew a couple of years ago. I have measured the individual noise exposure in each aircraft. The trouble is I cannot find or get information on the noise reduction factor of these ANR headsets. They appear to be ANR only (that is, without any passive hearing protection). There is no data on this in the specs or user manual, and the manufacture said they would respond to us weeks ago with this information but we are no further forward. The only bit of info I can find is that the ANR system is capabale af >125dB at 100Hz, which is not particularly useful. 

The headsets are LightSpeed Zulu 3 headsets (https://www.lightspeedaviation.com/product/zulu-3-anr-headset/)

Hoping someone has encountered a similar situation before and can shed some light.

Thanks

Grant