the sense of hearing is accomplished by a process known as auditory transduction the ear converts sound waves in the air into electrical impulses which can be interpreted by the brain as sound enters the ear it passes through the external auditory canal where it meets the tympanic membrane the tympanic membrane then vibrates in response to the sound sounds of a lower pitch or frequency produce a slower rate of vibration and sounds of lower volume or amplitude produce a less dramatic vibration higher frequency sounds produce faster vibrations the tympanic membrane is cone-shaped and articulates with a chain of three bones called the auditory ossicles they consist of the malleus the incus and the stapes the movements of the tympanic membrane vibrate the ossicles passing on the information of frequency and amplitude [Music] the stay Pease moves with a piston-like action which sends vibrations into a structure called the bony labyrinth the labyrinth is filled with a fluid called perilymph if it were completely closed an inflexible system the movement of the state bees would be unable to displace the perryland and therefore unable to send vibrations into the bony structure due to the flexibility of a membrane called the round window the stabies movement can displace the perilymph allowing vibrations to enter the labyrinth the corridor leading to the round window is found within the spiral portion of the bony labyrinth known as the cochlea vibrations produced by the state these are drawn into the spiral system and returned to meet the round window the portion of the spiral passage in which vibrations ascend to the apex of the cochlea is called the scale of vestibular the descending portion of the passage is called the skeleton Pony a third structure called the cochlear duct is situated between the scale of vestibuli and the scala tympani the cochlear duct is filled with a fluid called endolymph and when viewed in cross section the membranes separating the two fluid filled systems are visible they are reissner's membrane and the basilar membrane the membranes are flexible and move in response to the vibrations traveling up the scale of vestibuli the movements of the membranes then send vibrations back down to the skeleton Tony a specialized structure called the organ of Corti is situated on the basilar membrane as the basilar membrane vibrates the organ of Corti is stimulated which sends nerve impulses to the brain via the cochlear nerve the actual nerve impulses are generated by specialized cells within the organ of Corti called hair cells the hair cells are closely covered by a structure called the tectorial membrane as the basilar membrane vibrates the tiny clusters of hairs are bent against the tectorial membrane triggering the hair cells to fire the entire basilar membrane does not vibrate simultaneously instead specific areas along the basilar membrane move variably in response to different frequencies of sound lower frequencies vibrate the basilar membrane closer to the apex of the cochlea whereas higher frequencies produce vibrations closer to the base this arrangement is known as tonotopic organization together this sequence of events is responsible for our acoustic perception of the world around us [Music]