Originally Posted by
chevvron
On my one Chinook ride, we had the rear door open thoughout and it wasn't too bad, mind you everybody was wearing headsets which would have muffled the noise a bit.
A few years ago (about 2016 I think) I was out in my back garden 'slugging' (unfortunately we've never been blessed with a resident hedgehog) at 4.25am and on H3, about half a mile north of me and about 2 miles east of Bagshot Mast a pair of wokkas ambled along westbound at about 1000ft and I was amazed how little noise they made in the otherwise dead calm of the dawn; somebody on here said it was a new design of rotor blade.
Given the time of day, the sound could have been reflected upwards by a layer of cold air at ground level. The converse is also true in that I can hear traffic from many miles away on a cold and frosty morning. Once the sun gets to work, the sound disappears.