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?
Nope.
So what you hear as frequency is the variation of pressure- hi-low-hi-low-hi-low, right?
We tend to visualize it as a line going up and down, etc, but that’s just a conceptual aid.
To “cancel” noise, it plays a tone whose high and low pressure is out of phase but otherwise identical. So instead of hi-low-hi-low, it plays low-hi-low-hi noise, and you don’t “hear” it.
Great for tuning out the noise of a jet engine, and the loser who keeps trying to talk to you while you’re stuck in a tin can with a bunch of other sardines for 10+hours.
But that pressure is still there pushing against your eardrum, and no matter how good the pick up and driver is for the ANC, it’s never going to perfectly match noise anyhow.
There’s a reason most ANC ear cans are closed back- the passive noise isolation reduces the amount of work they have to do.
So what you’re telling me is, i should really be wearing hearing protection when i go underwater? All that pressure must be wreaking havoc on my hearing.