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AIM: How do we hear?
Opponent Process Theory
Hering proposed that we process four primary colors combined in pairs of red-
green, blue-yellow, and black-white.
Cones
RetinalGanglion
Cells
Color Constancy
Color of an object remains the same under different illuminationsWhen context changes, the color of an object may look different.
R. B
eau Lotto at U
niversity College, L
ondon
Audition
http://www.freemosquitoringtones.org/
AIM: How do we hear?
Hearing Range
• 40 Hz to 60,000 Hz – Dog’s
• 20 Hz and 120,000 Hz – Bat’s
• 20 to 20,000 Hz –Human’s
(Human voice range- 85- 255 Hz)
The Stimulus Input: Sound Waves
Sound waves result from the compression of air molecules.
Acoustical transduction: Conversion of sound waves into neural impulses in the hair cells of
the inner ear.
Sound Characteristics
1. Frequency (pitch)2. Intensity (loudness)3. Quality (timbre)
Frequency (Pitch)
Frequency (pitch):
determined by the wavelength
of sound.
Wavelength: The distance from the peak of one wave to the peak of the
next.
Intensity (Loudness)
Intensity (Loudness):
the amplitude, relates to the
perceived loudness.
Loudness of Sound
70dB
120dB
Richard K
aylin/ Stone/ Getty Im
ages
Quality (Timbre)
Quality (Timbre): Characteristics of sound from a zither and a guitar allows the ear to
distinguish between the two.
http
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Zither
Guitar
http://www.youtube.com/watch?v=p1FlDdNLkD4
http://www.youtube.com/watch?v=C9ZRS0F5t34
Overtones
Overtones: Makes the distinction among musical instruments possible.
The Ear
Dr. Fred H
ossler/ Visuals U
nlimited
The Ear
Outer Ear: Pinna. Collects sounds.
Middle Ear: Chamber between eardrum and cochlea containing three ossicle bones (hammer, anvil, stirrup)
Inner Ear: Innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs.
Cochlea
Cochlea: Coiled, bony, fluid-filled tube in the inner ear that transforms sound
vibrations to auditory signals.
Theories of AuditionPlace Theory
-Herman von Helmholtz -suggests that sound frequencies stimulate the basilar membrane at specific places resulting in perceived pitch.
http
://ww
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k
Theories of Audition
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.
SoundFrequency
Auditory NerveAction Potentials
100 Hz200 Hz
Frequency Theory: Volley Firing
• Alternated neural firing can achieve frequencies above 1000 Hz per second
Localization of Sounds
Because we have two ears, sounds that reach one ear faster than the other ear
cause us to localize the sound.
Localization of Sound
1. Intensity differences2. Time differences
Biaural Cues: Time differences as small as 1/100,000 of a second can
cause us to localize sound.
Hearing Loss
Conduction Hearing Loss: Hearing loss caused by damage to the mechanical system
Sensorineural Hearing Loss (nerve deafness): Hearing loss caused by damage to the cochlea’s receptor cells or nerves
Hearing Deficits
Older people tend to hear low frequencies well but suffer hearing loss when listening for high
frequencies.
Deaf Culture
Cochlear implants are electronic devices that enable the brain to hear sounds.
Cochlear ImplantDeaf Musician
EG
Images/ J.S. W
ilson ©
Wolfgang G
stottner. (2004) Am
erican Scientist, V
ol. 92, Num
ber 5. (p. 437)