I have two types of foam plugs, the softer ones don't work as well as the ones that are a harder foan, more coarse, and expand to a pretty tight fit. They are old, found a case of them in the workshop when we moved in here, I like them better. I'm so used to protecting my hearing, from shooting or power tools, one day I lost one my earplugs at work and had to ride home w/o one of them, I thought the noise was almost unbearable.
These are the better ones, they say 30db
These don't seem to work nearly as well for me.. but they say 32db
These claim 33db.
I shoot a very loud rifle, and earplugs alone will leave my ears ringing after one shot,
it takes BOTH earplugs AND jet-jockey hard headphones to make that level of noise bearable,
some motorcycles are probably nearly that loud.
Damaging level is 85db, a loud bike sitting revved still is probably 125db,
at speed with wind and traffic noise, who knows, 135db cumulatively?
If so, 33db just barely does the job.
Point is get very good earplugs. I see some rated 12 db, why even bother?
:ride
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