Download Module 19 Hearing Module Preview In the sense of hearing, sound

Module 19
Hearing
Module Preview
In the sense of hearing, sound waves are transmitted to
the fluid-filled cochlea, where they are converted to
neural messages and sent to the brain. Together, the
place and frequency theories explain how we hear both
high-pitched and low-pitched sounds. The mechanical
system that enables us to hear is fairly sensitive and
easily subjected to damage, causing hearing loss.
Module Guide
The Stimulus Input: Sound Waves and The Ear
Exercise: Auditory Demonstrations on CD
Lecture: Recognizing Our Own Voice
PsychSim 5: The Auditory System
19-1. Describe the auditory process, including the stimulus
input and the structure and function of the ear.
Audition, or hearing, is highly adaptive. The pressure
waves we experience as sound vary in amplitude and
frequency and correspondingly in perceived loudness and
pitch. Decibels are the measuring unit for sound
energy.
The visible outer ear channels the sound waves through
the auditory canal to the eardrum, a tight membrane
that vibrates with the waves. Transmitted via the bones
of the middle ear (the hammer, anvil, and stirrup) to
the fluid-filled cochlea in the inner ear, these
vibrations cause the oval window to vibrate, causing
ripples in the basilar membrane, which bends the hair
cells that line its surface. This movement triggers
neural messages to be sent (via the thalamus) to the
temporal lobe’s auditory cortex. Damage to the hair
cells accounts for most hearing loss.
Exercise: Locating Sounds
19-2. Contrast place and frequency theories, and describe
how we pinpoint sounds.
Place theory presumes that we hear different pitches
because different sound waves trigger activity at
different places along the cochlea’s basilar membrane.
Thus, the brain can determine a sound’s pitch by
recognizing the place on the membrane from which it
receives neural signals.
Frequency theory states 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
volley principle explains hearing sounds with
frequencies above 1000 waves per second.
Place theory best explains how we sense high-pitched
sounds, and frequency theory best explains how we sense
low-pitched sounds. Some combination of the two
theories explains sounds in between.
Sound waves strike one ear sooner and more intensely
than the other ear. We localize sounds by detecting the
minute differences in the intensity and timing of the
sounds received by each ear.
Hearing Loss and Deaf Culture
Lectures: Hearing Loss; A Quiet World—Living With Hearing Loss
19-3. Contrast the two types of hearing loss.
Problems with the mechanical system that conducts sound
waves to the cochlea cause conduction hearing loss. If
the eardrum is punctured or if the tiny bones of the
middle ear lose their ability to vibrate, the ear’s
ability to conduct vibrations diminishes. Damage to the
cochlea’s hair cell receptors or their associated
nerves can cause the more common sensorineural hearing
loss. Once destroyed, these tissues remain dead.
Disease, biological changes linked with aging, or
prolonged exposure to ear-splitting noise or music may
cause sensorineural hearing loss.
19-4. Describe how cochlear implants function, and explain
why Deaf culture advocates object to these devices.
Those who live with hearing loss face social
challenges. Cochlear implants are wired into various
sites on the auditory nerve, allowing them to transmit
electrical impulses to the brain. They help children to
become proficient in oral communication. The latest
cochlear implants also can help restore hearing for
most adults. Deaf culture advocates object to using the
implants on children who were deaf before developing
language. They note that deafness is not a disability
because sign is a complete language. Some also argue
that sensory compensation, which enhances other senses,
gives deaf people advantages that the hearing do not
have.