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What is the role of the round window in hearing?

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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 round window is a membrane-covered opening between the middle ear and the cochlea that plays a critical role in the physiology of hearing.12

Because the fluids within the inner ear are virtually incompressible, the movement of the oval window by the stapes would be ineffective if there were no way for the fluid to displace. The round window acts as a pressure-relief valve, moving in a reciprocal fashion to the oval window. When the stapes footplate pushes inward at the oval window, the round window bulges outward into the middle ear, and vice versa. This reciprocal movement allows the perilymph within the cochlea to vibrate, which in turn displaces the basilar membrane and stimulates the hair cells necessary for hearing. Without this mechanism, sound waves would be unable to effectively travel through the cochlear fluids.34