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How does the stapes move the oval window?

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Diagram showing auditory mechanisms in insects, including labeled illustrations of a scolophore organ, the mosquito ear with antenna shaft and scolophores, the cicada ear with auditory capsule and tympanic membrane, and the grasshopper ear with sensory body and tympanic membrane. — sound reception Auditory mechanisms in insects. (Left) A scolophore organ. (Top right) The mosquito ear. (Centre right) The ear of the cicada *Magicicada septendecim*. (Bottom right) The ear of the grasshopper.

The stapes, or stirrup, is the final bone in the middle ear's ossicular chain. It transmits sound vibrations to the inner ear by moving its base, known as the footplate, within the oval window.12

The stapes is held in the oval window by the elastic annular ligament, which allows it to vibrate freely. As sound waves strike the tympanic membrane, the resulting vibrations are transferred through the malleus and incus to the stapes. The middle ear acts as a transformer, concentrating these vibrations onto the small area of the stapes footplate, which significantly increases the pressure applied to the cochlear fluids.123

When the stapes moves inward, it pushes against the oval window, causing the round window to bulge outward in a reciprocal fashion. This mechanical action is essential for converting airborne sound into fluid vibrations within the cochlea, enabling the sense of hearing.3