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Bell Work
• Wavelength is to ______________ as
___________ is to brightness
– hue, intensity
– intensity, hue
– frequency, amplitude
– brightness, hue
– amplitude, intensity
Announcements
• Tomorrow-SUMMATIVE :D
• Next Thursday-Guest Speaker
• Monday, November 24-States of
Consciousness (Chapter 7)
Decibel
Intensity
hearing threshold
0
breathing
10
whispering
25
normal conversation
screaming child
jackhammer
chain saw
amplified rock concert
shout into ear at 20 cm
car horn
siren
threshold of pain
gunshot
jet engine
12-gauge shotgun
rocket launching
loudest audible tone
60
90
100
110
90–130
120
120
120
120–140
140
140
165
180
194
Hearing Loss
• Hearing loss and deafness can result from sound exposure, heredity,
ototoxic drugs (chemicals that damage auditory tissues), accidents, and
disease or infection. Conductive hearing loss results from damage to the
outer or middle ear, and sensorineural hearing loss results from damage to
the inner ear.
• Damage associated with conductive hearing loss interferes with the
efficient transfer of sound to the inner ear. Conductive hearing loss is
characterized by a loss in sound intensity. Voices may sound muffled, while
at the same time the individual’s own voice may seem quite loud. It can be
caused by anything that interferes with the vibration of the eardrum or with
the movement of the bones of the middle ear. Even a buildup of earwax can
lead to conductive hearing loss.
• An ear doctor can simply remove a buildup of earwax. It should be pointed
out, however, that you should never try to remove wax from your own ears.
You can too easily push the wax further into the ear canal and even damage
your eardrum. A common cause of conductive hearing loss in children is ear
infections. Other causes of conductive hearing loss are a punctured
eardrum or otosclerosis (a buildup of spongy tissue around the middle ear).
These can be treated through surgery.
Hearing Loss
• Sensorineural hearing loss is generally associated with damage to the hair
cells in the inner ear.
• When hair cells are damaged, their ability to participate in sound
transduction is compromised. If your hair cells are completely destroyed,
you will be unable to hear any sounds, no matter how loud they are. If the
hair cells are damaged, you may still hear sounds, but the sounds will be
distorted. Different hair cells respond to different pitches. Typically, hair
cells that respond to higher pitches are lost first. One reason is that the
basilar membrane vibrates more vigorously in response to higher pitches.
These vibrations can cause the delicate stereocilia of the hair cells to be
sheared off. One consequence of this damage is that it becomes more
difficult to understand the higher-pitched voices of women and children. It
also becomes more difficult to distinguish a person’s speaking voice from
background noise. The effects of noise-induced hearing loss may be
temporary or permanent, depending on the intensity and duration of the
exposure. Although a person’s hearing may recover from temporary, slight
damage to the hair cells, the complete loss of hair cells is irreversible in
humans.
Hearing Loss
• The phrase “too loud, too long, too close”
summarizes the causes of noise-induced
hearing loss. The intensity, duration, and
proximity of sound to the listener determine
whether or not damage occurs and if that
damage is reversible or permanent. Hearing
loss can result from a single loud noise, such
as an explosion, but more commonly results
from repeated exposure to less intense sounds
that are close by.