The round window is the most basal end of the scala tympani, and allows release of hydraulic pressure of perilymph that is caused by vibration of the stapes within the oval window. The eustachian tube connects the middle ear with the nasopharynx of the throat. Because the eustachian tube is shorter and has a more horizontal orientation in young children, it is less likely to open. Therefore, fluid collect more often within the middle ear space of young children. See our link on Serous Otitis Media for more detail on this.
Mechanical energy is transformed into the traveling wave pattern of the basilar membrane .
The vibrational patterns that are initiated by vibration of the stapes footplate set up a traveling wave pattern within the cochlea. This wavelike pattern causes a shearing of the cilia of the outer and inner hair cells. This shearing causes hair cell depolariztion resulting in all or none neural impulses that the brain interprets as sound. The horizontal, anterior, and posterior semi-circular canals are also part of our vestibular labyrinth, and inform our brains about rotational movement in space. The VIII nerve, also known as the auditory nerve, transmits information from the cochlear and vestibular labyrinth to our brains.