I never wear hearing protection when hunting.
The noise from a rifle has never bothered me a bit and yes I still have excellent hearing, my hearing has been tested.
That being said I would still recommend using hearing protection.
As far as a noise difference between 16" vs. 20" .223
I don't notice any, unless I'm in a covered shooting area or next to someone shooting them, then the 16" is noticably louder.
