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Perception of Hearing Notes

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McGill University
PSYC 212
Evan Balaban

The Auditory System: Perception of Hearing Hearing: perceptual experience of sound in the brain - identification of sound location - identification of sound quality A. Intensity and Loudness Loudness: mental impression of intensity - humans hear 20 - 20,000 Hz - intensity perception is influence by frequency 1. Audibility Thresholds Procedures 1) Minimum audible field (MAF) - open ear - loudspeaker in a room, free-field, natural 2) Minimum audible pressure (MAP) - closed ear - earphones - MAF appears to give lower threshold due to pinna amplification - minimum threshold chosen at 50% detection level Absolute Detection Thresholds - hearing sensitivity increases in 2000 - 4000 Hz range (mid frequencies) - minimal audibility curve is a function of threshold sound detection and frequency - hard to find absolute lowest frequency heard because it becomes a physical sensation What determines the minimal audibility curve? - conduction in inner/outer ear - mechanical response of cochlea - physiology of nervous system Absolute Sensitivity Factors - MAF lower than MAP by 6 dB (outer ear augmentation) - duration of sound - over 200ms, integration occurs, hearing is maximized - under 200ms, integration (temporal summation) doesn’t occur, hearing not maximized - binaural summation - hearing is the sum of pressures over the whole system - monaural is ~6 dB higher (less sensitive) Terminal Thresholds - highest/max pressure tolerable until pain - ~ 130 - 140 dB - dynamic range = suprathreshold until terminal threshold for frequencies 135 - 4000 Hz 2. Difference Thresholds - Weber constant for intensity discrimination ~ 0.1 - 0.4 1) larger difference needed @ higher intensities than lower intensities to produce a just noticeable difference 2) intensity discrimination not affected by sound frequency when single tones are used 3. Loudness Perception Steven’s psychophysics - sone scale 1 sone = loudness of 1000 Hz @ 40 dB, 10 sones = 10x 1 sone 2 sones = 1000 Hz @ 50 dB, 4 sones = 1000 Hz @ 60 dB “10 dB rule”: + 10 dB to double loudness, - 10 dB to half loudness - pressure more than doubles when loudness doubles - power function between loudness and sound pressure: L = K(P^0.67) L = loudness, K = constant (unit dependent), P = sound pressure Binaural Summation - loudness with binaural presentation is 2x monaural condition - loudness of ear 1 + loudness of ear 2 = total loudness Loudness Perception 1) increase intensity of sound, increase neural activity - auditory neurons restricted to ~40 dB - any intensity only stimulates a
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