It could help people who work around noise levels where they need protection but don't realize it.
I imagine hearing loss has got to be a spiraling hole people don't realize they are falling into.
Person has diminished hearing from long term persistent, or short term acute trauma, so hearing is diminished.
Person doesn't realize they have a problem so they turn up volumes and don't realize loud noises are in fact too loud, so they are less diligent about hearing protection.
Meanwhile, damage is still occurring and all the person realizes is that sounds are getting more and more muffled.
Is that an accurate thought?
Obviously tinnitus and immediate hearing loss would be detected, but I would think that long term hearing loss can progress increasingly faster and faster due to the above phenomenon. I've always had extremely sharp hearing. As a child I would get really angry with my parents as the TV would be turn up to what they perceived as normal levels, and to me it was actually painful. I could tell who came home based on the sound of their jingling keys while they were outside, and the house was closed up.
It's still pretty good, but finally in middle age I notice the volume is dialed down a bit. But I wear hearing protection even to cut my lawn, and I've started doubling up if shooting something big, or at an indoor range.