As a semi-relevant tangent, a bit of the neuroscience of hearing…
Your inner ear looks like this:
The three canals are your vestibular system; fluid moving through those, deflecting tiny hairs in the process, allows you to detect head movement and provides a large part of your sense of balance.
The snail-shell bit at the bottom is the sound detector. It’s also full of fluid and tiny hairs, which are connected to nerves that respond to movement of the hairs.
Any sound that hits the tympanic membranes (the “eardrum”) creates a wave in that fluid, which moves down the cochlea deflecting hairs as it goes. High frequency sound creates short rapid waves, low frequency sound creates long slow waves.
The system measures sound in two ways, described as “time” and “place”. Neither system is perfect; they each have a margin of error, so they only tell your brain that the sound is somewhere between frequencies x and y. However, by using two independent methods, you get much greater precision, as you can narrow the range of possibilities to just that area where the two ranges intersect.
|---------| System 1
|---------| System 2
|--| Combined precision
The “time” system works by using the entire membrane. It measures the time delay between pulses, and computes the frequency of the signal from that.
The “place” system makes use of the fact that the hair cells on the cochlear membrane are laid out in a “tonotopic” pattern. All that means is that the hairs at the start of the membrane are a bit stiffer, and the flexibility increases as you move further along. The stiffness of the hair affects the frequency at which it resonates most strongly, which allows the brain to determine frequency by looking at which spot on the membrane is generating the strongest response.
Acquired hearing loss is normally caused by excess sound pressure destroying some of the detector hair cells. It just physically breaks them. The stiffer, tuned-for-high-frequency hairs at the start of the membrane are more brittle and closer to the outside, so they’re the first to go.
This damage leaves the “time” system largely unaffected, but trashes the “place” system, particularly in the higher frequencies. The result is a person who can still detect sound, but has trouble discriminating between similar frequencies, particularly in the higher register.
