DO NOW: Put your homework packet together and get your reading notes out to be checked. THEN answer: Explain the Young-Helmholtz trichromatic theory of color vision. How is it different from the opponent- process theory?

AP Psychology Ms. Desgrosellier 11.20.2009 Hearing AP Psychology Ms. Desgrosellier 11.20.2009

Objectives: SWBAT define audition, and describe the pressure waves we experience as sound.  SWBAT describe the three regions of the ear, and outline the series of events that triggers the electrical impulses sent to the brain.  SWBAT contrast place and frequency theories, and explain how they help us to understand pitch perception.  SWBAT describe how we pinpoint sounds.  SWBAT contrast the two types of hearing loss, and describe some of their causes.  SWBAT describe how cochlear implants function, and explain why Deaf culture advocates object to these devices.

Hearing Audition: the sense or act of hearing. We hear sounds best when they are in the range of frequency of the human voice. We are fairly sensitive to faint sounds. We can easily detect differences between sounds (like recognizing a friend’s voice).

Stimulus Input: Sound Waves Sound waves create pressure changes that our ears detect. The ears then transform the vibrating air into nerve impulses, which our brain decodes as sounds. The amplitude of the waves determines the loudness.

Stimulus Input: Sound Waves The length of the waves determine the frequency (the number of complete wavelengths that pass a point in a given time). The frequency determines the pitch (a tone’s experienced highness or lowness).

Stimulus Input: Sound Waves Decibels: the measuring unit for sound energy. Prolonged exposure to sounds above 85 decibels can produce hearing loss A normal conversation is at about 60 decibels A passing subway train is about 100-decibels

The Ear Outer ear: visible part of the ear; channels the sound waves through the auditory canal to the eardrum.

The Ear Outer ear (pinna)

The Ear Eardrum: a tight membrane that vibrates with the waves. Middle ear: the chamber between the eardrum and cochlea. Hammer, anvil, and stirrup: a piston in the middle ear made up of containing three tiny bones that concentrate the vibrations of the eardrum on the cochlea’s oval window (membrane).

The Ear stirrup anvil Hammer Outer ear (pinna) Eardrum

The Ear Cochlea: a coiled, bony fluid-filled tube in the inner ear through which sound waves trigger nerve impulses.  looks like a snail! The vibrations on the cochlea’s oval window cause vibrations that move the fluid in the tube.

The Ear Middle ear stirrup anvil Hammer Outer ear (pinna) cochlea Eardrum

The Ear Basilar membrane: lined with hair cells that are bent by the vibrations from sounds and triggers impulses in the adjacent nerve fibers that converge to form the auditory nerve. The neural messages travel via the thalamus to the temporal lobe’s auditory cortex – and we hear!

The Ear Middle ear stirrup anvil Hammer Outer ear (pinna) cochlea Basilar membrane (in the cochlea) Eardrum

The Ear

The Ear

Perceiving Pitch place theory: in hearing, the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated. We perceive pitch based on where on the membrane it receives neural signals. It explains why we hear high-pitched sounds, but not low-pitched ones because they are not so specifically located on the membrane.

Perceiving Pitch Frequency theory: in hearing, the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch. The vibration of the basilar membrane matches the frequency of the sound wave. The brain can then read the pitch from the frequency of the neural impulses.

Perceiving Pitch Problem: individual neurons cannot fire faster than 1000 times per second – how can we perceive sounds about 1000 waves per second? Volley principle: neural cells can alternate firing so that by firing in rapid succession, they can achieve a combined frequency above 1000 times per second.

Locating Sounds Having ears on both sides of our head can help us locate sounds. Sound on the right side of you will reach your right ear faster. While sound travels so fast that the difference is tiny, our brains are able to process the difference. The just noticeable difference between each ear is just .000027 second. We are not as good at locating sounds directly above or below us because the sound strikes our ears at the same time.

Hearing Loss and Deaf Culture Conduction hearing loss: hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea. Can be caused by a punctured ear drum, loss of movement of the bones in the middle ear, or if the ear’s ability to conduct vibrations lessens.

Hearing Loss and Deaf Culture sensorineural hearing loss: hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerves; also called nerve deafness. Can by caused by disease, but more commonly the result of biological changes linked with heredity, aging, and prolonged exposure to too- loud noise or music. Once destroyed, these tissues stay dead, but a hearing aid may amplify sound enough to stimulate neighboring hair cells.

Cochlear Implants A device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea. Can help children learn oral communication and may also help them become less distractible and impulsive. Can also help restore hearing in most adults, but not if they never learned how to process sound.

Cochlear Implants Debate: 90% of deaf children have hearing parents. They want their children to be able to hear. Deaf culture advocates believe that people who can use sign language are not language- impaired at all because they can communicate. They see that being deaf doesn’t make you a disabled person, but a rather a person with a disability (labeling the person vs. labeling the disability).

Sensory Compensation Because the brain is plastic, people with a loss of one sense may have increased other senses.

Sensory Compensation For example, research has shown that: Blind musicians are more likely than sighted ones to develop perfect pitch. With one ear plugged, blind people are also more accurate than sighted people at locating a sound source. Blind individuals can better estimate the size of a carton of eggs than sighted people with their eyes closed. Deaf people’s auditory cortex can become responsive to touch and visual input.