Prune Towers, we tried ear plugs(specially moulded to that individual) and they worked quite well, however, they were a problem around the helipad when working outside the running helo what's more: we kept 'misplacing' the bloody things because of their size!!!
We now use Active Noise Reduction headsets(ANR) set inside the headphones. Headset Services @ Shoreham designed them for us.
We looked into the research that DERA had compiled over many ears(sic).
Basically there isn't anything available on the commercial helo market at the mo' that will reduce/cancel low frequency sound[MGB, certain engine frequencies, etc]. The best models on the market only cater for high frequency noise such as the turbine whines etc and it is these that apparently cause damage to the inner ear and not so much the low freq.
Be very wary of an 'off the shelf' model because they may have been designed to capture a very narrow spectrun of high freq noise found in anything from motorbikes to model a/c!!! These are not tailored to the helo market per se.
Usual saying: you gets what yer pay for....
