Amanda, Daniel, Scott, Hannah, Grant

1. Hearing a.k.a. audition Amanda, Daniel, Scott, Hannah, Grant

2. Basics of Sound • Sounds come in the form of waves • Wave’s frequency (measured in Hertz) determines pitch – how high or low a sound seems to us • Humans can hear between 20 and 20,000 Hz • Volume (how loud a sound is) is measured in decibels • Average office workplace is about50 dB • Normal conversation is about 60-70 dB • 90-95 dB is the level at which sustained exposure will result in hearing damage or loss • Loud rock concert – about 115 dB (that’s why you’re a little deaf after them)

3. Parts of the Ear(3 Main Sections) 1. Outer Ear • Auricle-visible part of ear, collects sound • Ear canal – simple tube that leads to… 2. Middle Ear • Eardrum(aka tympanic membrane) • Ossicles – stirrup, hammer, anvil; 3 tiny bones that receive vibrations from eardrum and transmit them to fluid of inner ear • Oval window – site where ossicles transfer vibrations to cochlea

4. 3) Inner Ear cont. • Cochlea – fluid filled, coiled structure that amplifies sound waves and converts from vibrations to neural impulses • Basilar membrane – membrane in cochlea that contains hair cells • Tectorial membrane – membrane covering Organ of Corti • Organ of Corti – located on basilar membrane, contains hair cells • Semicircular canals – 3 connected canals filled with fluid that detect movements

5. How We Hear 1) Sound waves enter auditory canal 2) Strike ear drum, cause it to vibrate 3) Vibrations travel through ossicles to oval window to cochlea where they are amplified and 4) Movement in fluid of the cochlea changes hair cells in basilar membrane 5) Hair cells connected to neurons send electrical impulses up the auditory nerve to the brain (transduction) 5) Brain interprets impulses as sounds, but also must locate where the sounds are coming from; spatial awareness comes from the auditory system as well as other sensory receptors

6. How We Hear cont. Place theory • Different frequencies cause different parts of basilar membrane to vibrate • Allows us to perceive pitch Frequency theory • Theory that all nerve impulses match exactly frequency of the sound waves • Pitch differentiation/analysis is carried out by brain centers

7. Hearing in the Brain • Electrical impulses from brain are taken to the temporal lobe • Neurons from 2 ears meet in brain stem, passing auditory info to both sides of brain • Signals arrive in auditory cortex for higher order processing • Brain recognizes distinctive patterns • Determines location of sound

8. Hearing Disorders Causes of hearing loss • Prolonged exposure to loud noises • Aging • Head trauma • Heredity • Diseases like meningitis Sensorineural deafness – deficit in impulses sent from cochlea to brain Central deafness – hearing loss from damage to auditory pathways; CNS is damaged, not ear Conduction deafness – inability to hear from damage to middle/inner ear

9. Treatments Cochlear Implant • Device containing microphone which picks up sound • Sends to auditory area of brain through electrical impulses • Implanted in inner ear • Treats severe sensorineural deafness Hearing Aids • Used to treat less severe hearing loss • Amplify sound

10. Deaf Culture In order to be considered part of deaf culture, one must: • Be deaf • Use sign language as the main means of communication There are different types of sign languages that deaf communities use