Sound = pressure waves Vary in frequency, amplitude Requires a physical medium Works in the dark, over long distances, out of sight lines
Tympanic membrane Ossicles Malleus ('hammer') Incus ('anvil') Stapes ('stirrup') Middle Ear Muscles Stapedius & tensor tympani
Ossicles amplify Air thinner than cochlear fluid Muscles dampen Acoustic reflex when sound intense or speaker vocalizes
Inner hair cells Transduce pressure waves Outer hair cells “Fine tune” transduction Alter stiffness of basilar/tectorial membranes
Auditory nerve (8th/XIII cranial) Cochlear nuclei Superior olivary nucleus L & R ear inputs mix Inferior colliculus
Frequency ~ pitch Mixture of frequencies ~ timbre (TAHMber) Place code Place on basilar membrane that vibrates most strongly
Interaural (between the ears) time/phase differences Low frequencies Interaural intensity differences High frequencies