Do you have a reference for this? I can't find anything that supports it (only the opposite!), and, intuitively, it doesn't make much sense.
My ear drum, and the hair cells behind it, do exactly one thing: respond to changes in air pressure. If the ANC isn't reducing air pressure forces, then why do I hear so little? The only way to hear less is to have less changing forces to disturbed them, is it not?
I assume the good ones designed with lowpass and aliasing filters to block out anything high frequency, but inaudible, that might damage hearing. These are absolutely not air tight, so there's nothing static, and the lack of bone-conduction sounds from walking makes me think it's keeping lower frequency pressure very well under control.
ANC is not actually cancelling out the second sound wave, it's exploiting an attribute of human hearing that two simultaneous out of phase sound waves are perceived as silence AFAIK. It doesn't mean that sound pressure goes away, and hearing damage can come from sound pressure that is too high for the hairs in your ear and damages those hairs as a result (ex: a lot of loud sound) is my hypothesis.
When I asked an audiologist if there has been research about ANC causing hearing damage, he said that it would be hard to get a grant structure that would work with it, since nobody is making money from it, and there hasn't been.
In tinitus, the frequency that people hear is around 4000hz, because that is where the first major bend in the cochlea is. It means that the loud sound that you hear doesn't necessarily have to be a specific frequency to damage hearing in that frequency either.
I think his idea is that some non planar wave within the ear would mean that the wavefronts would not be exactly matched for all reflection paths to and within the cochlea. This would mean the phase would not remain as they travel through the cochlea and could construct at some point around the hair cells.
But, considering the wavelength of 20kHz is 1cm and the ear canal is about 0.7, I can't imagine there's much room for anything but a nice planar wave heading down the canal, let alone within the cochlea.
My ear drum, and the hair cells behind it, do exactly one thing: respond to changes in air pressure. If the ANC isn't reducing air pressure forces, then why do I hear so little? The only way to hear less is to have less changing forces to disturbed them, is it not?
I assume the good ones designed with lowpass and aliasing filters to block out anything high frequency, but inaudible, that might damage hearing. These are absolutely not air tight, so there's nothing static, and the lack of bone-conduction sounds from walking makes me think it's keeping lower frequency pressure very well under control.