A comment by Pais prompted me to bring this topic to members attention, again.
First let me say that to my knowledge there is no such thing as a quiet helmet. A tight helmet is the best you'll do ( they all loosen with time) but too tight to start with and you will experience a sore head pretty soon.
I am sure that my poor hearing is mostly a result of for years riding without ear plugs. This type of hearing loss is permanent and for me is progressive. I have, for the last several years, always worn earplugs unless to the local shops just 1km away but these precautions are just too late.
The greatest problem for me is that it prevents normal conversation unless one on one with no ambient noise. Otherwise I'm constantly asking people to repeat what they said. People tire from repeating themselves very quickly.
I realized just how bad it had become for me when several years ago I joined a group of off-road power jockeys ( Ulyssians and fast, let me tell you) non of whom I'd met before. On the first night around a blazing fire in the pub ,with lots of noise going on I could not understand a single word spoken (OK Chops .. I was jober as a sudge
) Rather than stand there and nod and grin like the Cheshire Cat, I ate dinner on my own and went to bed early. It really gutted me and made me realize how bad it had become. It's an anti-social problem and it is permanent, you will regret it when it's far too late if you don't use plugs.
Also there is the tinnitus that can at times drive you to the brink...and I rarely hear a bird song anymore.
Always wear your ear plugs!!