The stapes, the smallest bone in the body, is what presses vibration onto the oval window so sound can travel on into the cochlea. The higher the frequency, the closer to the base its resonance point sits, while low tones reach the apex, exactly the tonotopic map covering the 20 Hz to 20 kHz range. The same organ also handles balance: every head turn leaves the endolymph in the semicircular canals lagging a beat behind, deflecting the cupula.
The stapes, the smallest bone in the body, is what presses vibration onto the oval window so sound can travel on into the cochlea. The higher the frequency, the closer to the base its resonance point sits, while low tones reach the apex, exactly the tonotopic map covering the 20 Hz to 20 kHz range. The same organ also handles balance: every head turn leaves the endolymph in the semicircular canals lagging a beat behind, deflecting the cupula.
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