Well it sounds like the best possible protection is the CEP system in a helmet. That way you get a lid plus sealed ear cups plus in-ear plugs. Looking at the CEP link though it looks like the CEP plugs in on the outside of the lid and then presumably the cable goes to the plug in your ear. Doesn't this then mean that the cable goes between the ear cup seal in the lid and your head? Is that not a bit of an issue?
Has anyone found a more or less definitive answer to this question? I searched for "bone conduction" but found no clear cut answer to whether this is a problem in light aircraft. At the airfield the other day I heard someone else mention this as a problem with the Clarity's too.
We're probably not going to find a specialist to answer this on pprune but I wonder if a letter to a well known flying mag or two might get them to research an article on it? As stik has pointed out though that his set keeps breaking, that puts me off somewhat!
I have a US Gentex helmet
Where did you get it? The really long helmet thread linked above has links to US suppliers but none in the UK that I can see. Headset Services in Shoreham is the only supplier that gets much mention and not in a positive way. Anyone know how much a PNR Alpha costs from them? There's no price on their website.