Your inner ear is a Fourier transform made of meat. The cochlea is a coiled ramp, stiff at one end and floppy at the other, so a high note shakes loose one spot near the base and a low note a spot near the tip. Pitch becomes PLACE — which is why a cochlear implant just stimulates the right position. Slide the frequency and watch the resonance travel.
The basilar membrane is tonotopic: its stiffness and width vary from base to apex, so each place resonates at a characteristic frequency — the Greenwood function f(x)=A(10^(αx)−k) maps position to frequency (von Békésy’s traveling wave, Nobel 1961). A pure tone peaks at ONE place; a chord at several; the nerve reads pitch as WHICH fibres fire. A fail-loud self-check throws unless the mapping is monotonic (base = higher frequency than apex). Cochlear implants exploit exactly this. ◆ real auditory neuroscience, node-verified.
The Greenwood place-frequency map with a peaked traveling-wave envelope (idealised, passive); the real cochlea is actively amplified and phase-locks at low frequencies too — the pitch-to-place mapping is the exact backbone.