Earplugs are a definite. I wish I listened to my supervisors at work because after working only 5 years in a 100+ decibel environment, I have hearing loss. On the plus side though, I get disability haha.
I use custom from a hearing guy who also rides a 916. I've also tried EarMould (Australian) and reckon the custom from the hearing guy are much better. they are smaller, easier to fit and I could take them back if they weren't a great fit within the first three months and get another set.
Another good noise reducer is a turtleneck tucked into the chin. Great on cold rides but on a hot day ear plugs are better.
there is also an added bonus especially on the track in that you change gear at 1,000 rpm more due to the lesser noise with the ear plugs (assumes you change by the engine noise rather than the tacho which is easy with after market pipes on a Ducati but damn near impossible if you ride a 4C bike.
I'm still looking for one I use regularly. I've tried just about all of them: custom silicone got loose/loud after a few months, ridged silicone hurt after a bit, foam take to long to put in (expanding). I like the noise canceling ones best, but some work loose a little and actually cause an echo louder than without them!
I bought a box of 500 pairs many, many years ago. I can't stand to ride without them anymore. And if I lose them, no worries, I have extras. In fact, I keep extra packs in the tail, coat pocket, etc.
Now, after so many years, I am running low. About time to order some more. I use the orange ones that are tapered off to a point. They work great. I had others that would bother my ears after a couple hours but these don't.
that's what I've been using and seems to give the best db reduction of any I've used. Even when rated the same. However, on the timber jack skidder I find I need
ear plugs and ear muffs. That's why I make my son run it.