Transcript PSYC 330: Perception

PSYC 330: Perception
Auditory Processing
The Basics
What is sound?
When I speak……
• Vibration in vocal cords 
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Displacement of molecules in the air
These displace adjacent molecules
Wave travels across the room
Enter your ear
• Cause vibration in your auditory
apparatus 
• You “hear” what I say
• Sound dissipates as it moves away
from the source
• Sounds is REALLY slow 760 mph
Qualities of sound
Sound Quality
Perceived As
Measured By
Amplitude
Loudness
Decibel (dB)
Frequency
Pitch
Hertz (hz)
Complexity
Timbre
Fourier (Spectra) Analysis
A note on notes
Sine wave – pure tone
Complex waves – multiple sine waves
Fourier analysis
- relative height (intensity/amplitude)
of each individual frequency in
sound (pg 247)
• Fundamental – root tone
• Harmonics – overtones/halftones
Harmonics
Fourier analysis
The hardware
Rock the middle ear,
dude!!!
Middle ear mechanisms:
Malleus, incus, stapes
 amplify
Tensor tympani, stapedius
 acoustic reflex
the cochlea
http://www.youtube.com/watch?v=PeTri
GTENoc
Sound
transduction
MECHANOELECTRICAL
transduction (MET)
Organ of Corti
Stereocilia
Tip links
MET is FAST and EXTREMELY SENSITIVE
Intensity coding
14,000 hair cells (vs. 100 million rods and cones)
Sound intensity Shear intensity  Greater stretching more NT
Pitch coding - place
http://www.youtube.com/watch?v=dyenMluFaUw
Afferent (inner hair cells) and efferent (outer hair cells)
Place theory
• Why do different parts of the basilar membrane get
displaced differently relative to frequency?
• Base is stiffer  more reaction to higher frequency
• Apex is wider and more flexible  more reaction to
lower frequency
• Neurons that make up the auditory nerve tonotopic
 voila! Perception of pitch
Pitch coding – freq.
• Phase locking – auditory nerves produce action
potential at specific, consistent point in the phase of
the sound wave
• Phase locking provides information for temporal
coding
• Volley principle
Phase locking
Brain or bust!
• Auditory nerve  cochlear nuclei (medulla)
• Superior olive
• Inferior colliculi
• Medial geniculate nucleus
• Auditory cortex
• Tonotopic organization
• AI, belt cortex, parabelt cortex
PSYCHoAcoustics
Thresholds change across frequency
psychoacoustics
• Factors influencing thresholds
• Species
• Frequency
• Equal loudness contours
• Temporal integration
Hearing loss
• Conductive hearing loss
• Sensorineural hearing loss
• Relationship to noise
exposure
• Relationship to normal
aging