Nate, of all the noise reduction units that I've looked at none of them reduce dB as much as the good foam ones, they all should have a rating on them and the highest I've found is 31dB and that was the foam type.
Knowing what dB's your equipment runs at and what level is non harmful will help you decide which unit will work for you.
I suffer from tinnitus from years of playing in bands and shooting, so I lean toward the foam whenever can, especially when running the louder machinces like the jointer, router and planer.
Al
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