Psychology 3041/6014 Spring, 2014 1 of 8 THE AUDITORY SYSTEM 1. Physical Stimulus: Sound • Vibration of an object leads to compressions & rarefactions of the material in 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.) Cliché: If a tree falls in the forest, and no one is there, does it make a sound…? 6 dB change means a doubling in intensity Pthreshold = 0.0002 dynes/cm2 =20 µPa = SPLPsychology 3041/6014 Spring, 2014 2 of 8 2. Perceptual Attributes (Psychological experience of physical attributes) a) Frequency ☞ Pitch b) Amplitude ☞ Loudness c) Complexity i. “richness” ii. “brightness” iii. “timbre” Key point: there is a physical stimulus, with physical attributes that are essentially incontrovertible; there are also perceived, psychological descriptions of the stimulus that can change for a number of reasons Both top-down and bottom-up processes at work in affecting perception of sounds DEMO: Spectral Components How is this like time perception?Psychology 3041/6014 Spring, 2014 3 of 8 3. Anatomy of the Auditory System Outer ear, middle ear, inner ear/cochlea, auditory nerve, auditory pathway, auditory cortex a) Outer ear i. Pinna (“ears”) ii. External auditory canal iii. Eardrum – tympanic membrane b) Middle ear i. Ossicles (malleus, incus, stapes) ii. Acoustic reflex c) Inner ear (cochlea) i. Cochlea (anatomy only, today)Psychology 3041/6014 Spring, 2014 4 of 8 d) Auditory neural pathway i. Cochlear nerve ii. Central auditory pathway (up to auditory cortex) Acronym Mnemonic:Psychology 3041/6014 Spring, 2014 5 of 8 4. Functioning of the cochlea a) Basic transduction process i. RATE theory ii. PLACE theory (Traveling wave along basilar membrane) iii. Combination With only 3500 inner hair cells, how can we determine all the complex sounds?Psychology 3041/6014 Spring, 2014 6 of 8 b) Hair cell functioning i. Inner hair cells ii. Outer hair cells iii. “Characteristic frequency” of auditory nerve fiberPsychology 3041/6014 Spring, 2014 7 of 8 5. Auditory Cortex a) Pathway (recall from previous lecture) i. Primary Auditory Receiving Area (A1) ii. “Core” = A1 + some surrounding areas iii. Secondary auditory cortex iv. Auditory association cortex b) Tonotopic map c) Columnar arrangement d) Plasticity of perception (See next page)Psychology 3041/6014 Spring, 2014 8 of