THE AUDITORY SYSTEMPsychology 3041/6014 Spring, 2019THE AUDITORY SYSTEM1. Physical Stimulus: Sound- Vibration of an object leads to compressions & rarefactions of the materialin the object- This can be transferred and transmitted to other media (like air)Can describe the sound in terms of physical properties:a) Frequency (Hertz, HZ)b) Wavelength (meters, m)c) Amplitude (decibels, dB)d) Complexity (spectrum, etc.)1 of 10Cliché: If a tree falls in the forest, and no one is there, does it make a sound…?6 dB change means a doubling in intensityPthreshold = 0.0002 dynes/cm2=20 µPa = SPLPsychology 3041/6014 Spring, 20192 of 10Psychology 3041/6014 Spring, 20192. Perceptual Attributes (Psychological experience of physical attributes) a) Frequency  Pitchb) Amplitude  Loudnessc) Complexityi. “richness”ii. “brightness”iii. “timbre”Key point: there is a physical stimulus, with physical attributes that are essentially incontrovertible; thereare also perceived, psychological descriptions of the stimulus that can change for a number of reasonsBoth top-down and bottom-up processes at work in affecting perception of sounds3 of 10DEMO: Spectral ComponentsHow is this like time perception?Psychology 3041/6014 Spring, 20193. Anatomy of the Auditory SystemOuter ear, middle ear, inner ear/cochlea, auditory nerve, auditory pathway, auditory cortexa) Outer eari. Pinna (“ears”)ii. External auditory canaliii. Eardrum – tympanic membraneb) Middle eari. Ossicles (malleus, incus, stapes)ii. Acoustic reflexc) Inner ear (cochlea)i. Cochlea (anatomy only, today)4 of 10Psychology 3041/6014 Spring, 2019d) Auditory neural pathway i. Cochlear nerveii. Central auditory pathway (up to auditorycortex)Acronym Mnemonic:5 of 10Psychology 3041/6014 Spring, 20194. Functioning of the cochleaa) Basic transduction processi. RATE theoryii. PLACE theory (Traveling wave along basilar membrane)iii. Combination6 of 10With only 3500 inner hair cells, how can we determine all the complex sounds?Psychology 3041/6014 Spring, 2019b) Hair cell functioningi. Inner hair cellsii. Outer hair cellsiii. “Characteristic frequency” of auditory nerve fiber7 of 10Psychology 3041/6014 Spring, 20195. Auditory Cortexa) Pathway (recall from previous lecture)i. Primary Auditory Receiving Area (A1)ii. “Core” = A1 + some surrounding areasiii. Secondary auditory cortexiv. Auditory association cortexb) Tonotopic mapc) Columnar arrangement8 of 10Psychology 3041/6014 Spring, 2019d) Plasticity of perception(See next page)9 of 10Psychology 3041/6014 Spring, 201910 of