Hi, docmus,
As a 64 yrs old male, wearing two hearing aids, I do value what little hearing I have left. Mine was due mostly to ear infections.
I do know that being subjected to prolonged loud sounds can eventually cause hearing loss, told to me by my ENT Specialist, and also from others working around loud equipment for years, now almost deaf.
I don't ride bikes, but have done much research on the web, looking for something that might work for you.
So far, here is a link:
Ear Plug - Earplugs - Hearing Protection - webBikeWorld
The link only shows some more types of ear "plugs". What you really need is a type of ear covering, such as a "gun shooters" ear muff, muffling the sound where it is barely audible. I have a pair of those, but they couldn't be used under a helment.
Hopefully, you can find some type of ear insert, that will not be too uncomfortable; even when worn all day long. There are many, many different types. I do wish you the best, and good luck.