Explain how sound is perceived by the ear, including the roles of the eardrum, bones of the middle ear, oval and round windows, and the hair cells of the cochlea.

·      Sound travels as pressure waves in the air which push the membrane of the eardrum, causing it to vibrate. The degree of vibration will vary according to the frequency and amplitude of the sound waves.

·      The eardrum pushes on the bones of the middle ear (the ossicles), which magnify the vibrations (~ 20 times).

·      The ossicles push against the oval window, displacing fluid within the cochlea.

·      Movement of the cochlear fluid affects the position of cilia on sensory hair cells. Cilia on hair cells vary in length and each resonates to a different frequency of sound

·      Activation of the hair cells generates nerve impulses which are transmitted via the auditory nerve to the brain 

·      The kinetic motion of the cochlear fluid is dissipated (dispersed) by the movement of the round window.