Originally Posted by
trip
ANR does nothing for the high frequency noise like wind and jet engines!
That article is suspect.
Nov. 2010 Plane and Pilot:
Mostly, ANR attenuates frequencies in the lower spectrum, from about 20 Hz to around 300 Hz, with peak reduction at 70-150 Hz. Studies have shown that peak noise levels generated by the propeller, engine and exhaust all combine around the 100 Hz point—precisely the area that ANR attenuates best. Higher-frequency noise is caused mostly by air flowing over the cockpit and fuselage. Most ANR headsets don’t attenuate high frequencies.
The article cites no sources (or even states "studies have shown") in the section where it identifies jet flight deck noise as "higher frequency noise". It uses general terms, like "most ANR headsets". Which ones are included in 'most', which ones aren't? What data is this statement based on?
Boeing did a
study to reduce flight deck noise in the 737NG, the results of which were discussed in May 2004. At the "pilots right ear" @ 35,000 ft and .78 M, the loudest noise was @ the 225 Hz frequency, and the greatest noise was between the 150 - 300 Hz Frequency range. Incidentally, these are around the same frequencies that Plane and Pilot identifies as the ones ANR works best at. Furthermore, the loudest noise in a 737 flight deck in the study was from the "ECS" (Environmental Control System). While the "Turb. Boundary Layer" is the highest contributor to noise @ 600 Hz and above, the overall noise is almost 20 dB than @ the 225 Hz peak. In short, the loud noise is where ANR works best at making loud noise go away.
As
the US Navy has found:
We are unaware of an industry standard to evaluate the protectiveness of Active Noise Cancellation (ANC) and Active Noise Reduction (ANR) products due to their dynamic attenuation properties.
There is simply not an objective way to evaluate ANR headsets right now against each other.
However, the
results of the 45th Navy Occupational Health & Preventive Medicine Conference Audiology Session are clear; the only noise reduction method to achieve the highest level of noise reduction is "Active Noise Reduction".
If you double up (earplugs inside your headset) it'll work better, ANR or not. That's a better option for hearing protection, but often won't work in a non-hot mic environment. The best option is wearing a "custom deep insert ear plug" (goes beyond the second bend in the ear canal) under your headset, and is the option Navy recommends on Aircraft Carriers (except for the LSO, b/c he needs to be able to communicate aurally, as well as hear the changes in thrust of landing aircraft).