Psychology 3041/6014 Spring, 2014 1 of 4 AUDITORY LOCALIZATION 1. The Need to Locate Sounds First, why do we need to localize sounds? Both bottom-up and top-down processes at work. 2. Demo 3. Recall a) Sound b) The Auditory System c) The Ear i. Pinna shapes sound. How? ii. Middle ear shapes sound. How? d) Neural Pathways i. How does(do) the neural pathway(s) affect sound perception? e) Cortex Regions i. Wernicke’s area of temporal lobe ii. Brocca’s area in the frontal lobePsychology 3041/6014 Spring, 2014 2 of 4 4. Monaural Location Cues a) Level (Loudness) Differences 5. Binaural Location Cues a) Interaural Time Differences i. Coincidence detectors. ii. The effectiveness of ITDs is limited to about 3000Hz. iii. The location of the neurons that detect ITDs is in the superior olivary nucleus, or superior olivary complex, in the medulla. iv. Cone of Confusion b) Interaural Phase Differences - For frequencies below 1000 Hz, we can also detect “phase” differences in the soundsPsychology 3041/6014 Spring, 2014 3 of 4 c) Interaural Level (Intensity) Differences i. Head shadow ii. Greater than about 1000 Hz iii. Size (of the head) matters iv. Neurons that detect ILDs in the superior olivary nucleus d) Spectral Cues i. Spectral characteristics of a sound are used to localize it. ii. Front-back reversals. e) Cue Combination i. Below 1000 Hz: Phase Differences & Time Differences ii. Between 1000 – 3000: Time & Intensity Differences iii. Above 3000: Intensity Differences iv. Spectral cues play a role in all frequency ranges.Psychology 3041/6014 Spring, 2014 4 of 4 6. Top Down Cues a) ILDs and ITDs are really low-level, brainstem sound processing cues. Spectral cues rely on learning, but not so much on knowledge. b) We can also use knowledge to help localize a sound. 7. Mis-Location a) Why do we mis-locate sounds in the following situations? i. Sounds directly in front vs. directly in back? ii. Sounds in a room with lots of echoes? iii. Sounds played over
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