If I recall correctly the maximum Noise Reduction Rating (NRR) for earplugs and earmuffs is around 30db. You can combine the two for a slight increase in hearing protection but you still hit a limit because of bone vibration.
Is there PPE out there to go even further beyond this? Where would it be commonly used?
I doubt that, mate.
The thing is that it needs to be literally perfect polarization flipping to protect you. ANC as we know isn’t perfect; it doesn’t perfectly cancel sound and create absolute silence. You’re still potentially vulnerable to high SPL
Show me electronic ear pro that doesn’t have passive noise reduction.
I’ll wait.
The vast majority are adding ambient low-level noise back in rather than removing loud noises with active noise cancellation.
The electronics are similar if not identical, mind, but there’s a reason active noise cancellation in things like the Bose headphones don’t get an NRR or SNR test done. Because they’re not ear pro
It’s because active noise cancelling is bad at cancelling sudden sounds, so many types of noise people want to protect against (gunshots, metal clanging at a construction site) would be poorly attenuated by current active noise cancellation technology. This is a not really a physics issue, just an active noise cancellation technology issue. Fundamentally active noise cancellation can and does reduce sound pressure, because the speaker basically “pushes against” the incoming pressure waves to flatten them out.