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Psyc 102

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Intensity. Frequency (x2=) Pitch (=1 octave) Phase (of 2 waves) Stereo direction ... Intensity difference (sound shadow): Best for high frequencies ... – PowerPoint PPT presentation

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Title: Psyc 102


1
Psyc 102
  • HEARING

2
If a tree crashes to the ground in an uninhabited
forest, does it make a sound?
  • Physics Yes, mechanical waves
  • Psychology No, no resulting sensation in a brain

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Stimulus Sensation (physics)
(psychology)
  • Amplitude Loudness
  • Intensity
  • Frequency (x2) Pitch (1 octave)
  • Phase (of 2 waves) Stereo direction

6
Hearing threshold
  • Faintest sound you can just hear
  • Low threshold high (good) sensitivity
  • Threshold is lowest at 1--5 KHz

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  • Audiogram (Hearing curve)

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Evolution of Hearing from the Lateral Line System
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The frog as a resonator
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Next
  • Anatomy -- more details
  • Deafness
  • Sound localization
  • Selective listening

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Cochlear hair cells
  • Inner hair cells
  • 25 of total hair cells
  • 95 of input to brain

Outer hair cells 75 of total hair cells Only 5
of input to brain Receive descending
fibers Probably little motors to stiffen basilar
membrane
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  • A 2-hour exposure to loud noisesimilar to a loud
    rock bandhas seriously damaged the hair cells of
    a cat's inner ear. All the tall cilia on the
    right of this picture have disappeared or fused
    together and fallen over.

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  • When this bundle of 50 to 60 cilia at the top of
    a hair cell vibrates in response to sound, the
    hair cell (from a bullfrog's inner ear) produces
    an electrical signal. Tiny tip links can be seen
    joining the tops of shorter cilia to the sides of
    taller ones (arrow).

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Hearing and Deafness
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  • Clinical audiogram (Hearing loss)
  • Normal hearing horizontal line at top 0 dB
    hearing loss
  • (Up is good)

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Causes of deafness
  • Disease (rare)
  • Noise
  • Age (related to noise exposure?)

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Causes of deafness 1. Menieres Disease
  • Fluid in the inner ear.
  • Vertigo (dizziness)
  • Tinnitus (ringing in the ear)

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Causes of deafness 2. Noise
  • Temporary threshold shift
  • Boilermakers disease
  • Artillery officers
  • Eustachian tube
  • Rock music?
  • Dentists Tonal dip

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Causes of deafness 3. Age
  • Presbyacusia high frequency loss (gt5KHz)
  • Caused by cumulative exposure to noise?
  • Mabaan tribesmen in Ethiopia
  • 85 year old in Amsterdam previously blocked ear
    like 30 year olds

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Two kinds of deafness Conduction
deafness Nerve deafness
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Conduction deafness
  • Eardrum becomes slack with age
  • Perforated eardrum
  • Broken ossicle can be replaced surgically

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Nerve deafness
  • Destruction of cochlear hair cells
  • Acoustic neuroma
  • Difficult to treat
  • Use a hearing aid

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Sound localization
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  • Sound localization
  • Intensity difference (sound shadow) Best for
    high frequencies
  • Time difference Best for low frqeuencies

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Relative intensity (Sound shadow of head)
  • Sound frequency
  • 100 Hz
  • 1000 Hz
  • 10,000 Hz
  • Intensity difference (dB)
  • 0
  • 30
  • 80

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Relative delay (Time difference at 2 ears)
  • Direction
  • 0 (ahead)
  • 2
  • 30
  • 90 (max)
  • Delay
  • 0 msec
  • 40 microsec
  • 270 microsec
  • 680 microsec

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  • Gloved Dr. Dan Feldman in Knudsens lab at
    Stanford prepares an owl for a hearing
    experiment.

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  • After wearing prism spectacles a few months, this
    owl began to miss auditory targets as the sound
    localization system in its brain tried to
    harmonize with the visual system, which received
    erroneous cues.

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  • 5 meter sphere at Wright Patterson Air Force
    Base in Dayton, Ohio. 277 loudspeakers. 6 meter
    cubical anechoic chamber Listeners in
    localization experiments indicate perceived
    source directions by placing an electromagnetic
    stylus on a small globe. (Mark Ericson and
    Richard McKinley.)

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  • Anechoic chamber

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Sound localization by Ormia, an acoustic
parasitic fly
  • Phonotaxis like you wouldnt believe
  • Slides from Dr. Roberts, University of Toronto

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Attention selective listening
  • Can you attend to two things at once?
  • The cocktail party problem How are we able to
    attend selectively to one voice out of many who
    are speaking?

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Questions in selective listening
  • How can we attend to only one voice (the cocktail
    party problem)?
  • Ans We use cues of pitch/timbre direction.
  • Can we attend to two voices at once?
  • Ans Mostly not.

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Shadowing occupies attention
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Selective attention how much of the weather
forecast will he hear while shadowing the woman?
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Meaning CAN guide selective listening Left ear
Once upon a.....papers today? Right ear Have
you read.....time there was a king.
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Changes in unattended (unshadowed) message which
are
  • HEARD
  • Male changes to female voice
  • Voice changes to music
  • NOT HEARD
  • English changes to French

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Threshold for hearing your OWN NAME is lower than
for other sounds
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