(The question has its origin because I asked myself in how far frequencies outside our perception can harm our hearing.)
First of all, the energy of a mechanical wave (in this case, the sound wave, which stimulates periodic movements of a gas) is proportional to both amplitude and frequency. Often, I read that it is written that energy depends only on amplitude, but when I have two waves with the same amplitude, and one has a higher frequency than the other, it apparently carries more energy. It has a shorter wavelength and moves the molecules much faster over the same distance. Since $E = F * s$, a wave with a higher frequency must carry a greater force (and therefore energy) to overcome the inertia of the molecules more quickly.
I'm not entirely familiar with how the ear works, but I do know that it has three sections. Waves enter through the outer ear, continue to vibrate the eardrum with their frequency, the middle ear amplifies this, and then somehow it goes into the inner ear, where there's a fluid-filled cochlea with hair cells. Certain frequencies can only reach specific spots due to the cochlea's geometric structure, allowing differentiation of pitch. Specific hair cells vibrate more strongly for certain frequencies, opening ion channels and sending signals to the brain, or something like that.
However, what I'm wondering now is whether it's really about the geometric structure or the fact that the hairs are of different lengths, thus having different natural frequencies, and frequencies that match their natural frequencies simply stimulate the right hairs through resonance? If that's the case, one can consider it similar to a forced oscillation, for example, when ultrasound reaches the hairs, we're far from the resonance case, so the hairs vibrate at ultrasound frequencies, but the displacement is extremely small, is that the reason they don't transmit signals?
How can I understand this? And if ultrasound stimulates the hairs to tiny vibrations, where does the rest of the ultrasound wave energy go? Do the hairs heat up, or do they simply reflect it (since in non resonance case the energy transfere between an exciter and oscillator isn't really good... try to excite a spring with a weight attached to it with a significantly faster frequency than its natural frequency from above, and you'll see that even when you wiggle it with high amplitude, the oscillator hardly moves from its position but only twitches faintly at your specified frequency, so same frequency but lower amplitude means the energy almost stays in the exciter itself)?
TLTR: Are vibrations in the ear stimulated at frequencies beyond our perception, and what is the reason we don't perceive them even when we increase the amplitude (decibels)? (And I'm referring to vibrations that don't originate through bone conduction, I've also read about this possibility.)