Sensation & PerceptionSensation & PerceptionCh. 12: Sound Localization© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)Main topicsMain topicsAuditory localizationPerceptual groupingpgpgch 12 1• Dan Levitin and his interview (NPR)•http://www psych mcgill ca/levitin/http://www.psych.mcgill.ca/levitin/ch 12 2ch 12 3ch 12 4Law of similarityLaw of similaritySimilar things are put togetherch 12 5ch 12 6Do you see a spinal motion? Thisch 12 7Do you see a spinal motion? This picture is called “Dance.” Do you see why?Perceptual organization• Grouping in music?• DemonstrationSt t i i–Structure in musicch 12 8Sound localization• Demonstration:–Where does this sound come from?Where does this sound come from?–YouTube Ventriloquist (America's Got Talent)YouTube Ventriloquist (America s Got Talent) • http://video.google.com/videoplay?docid=-4976377170423854180&q=ventriloquist&total=2398&start=0&num=10&so=0&type=search&plindex=4ch 12 9ch 12 10• 3 different coordinates–The horizontal coordinateThe horizontal coordinate– The elevation coordinate–The distance coordinateThe distance coordinatech 12 11Figure 12.2 Measurements of sound localization ability. Red squares indicate the actual sound locations, and the circles are the listeners’estimates of their location Longer lines connecting the squares and circlesch 12 12and the circles are the listenersestimates of their location. Longer lines connecting the squares and circles indicates less accurate localization.Identifying the sound source in the horizontal coordinate• Interaural differences– Interaural time differences•Capture the difference in the time that a sound reaches the left and right earsInteraural level differences–Interaural level differences•Capture the difference in the level of the sound intensity (sound pressure level) that a sound reaches hlf dihch 12 13the left and right earsch 12 14Identifying the sound source inIdentifying the sound source in the elevation coordinate• Spectral cues– Capture the way the head and pinnae affect sound frequenciesch 12 15• Depending on the level of elevation theelevation, the same sound enters the ears in a different manner.ch 12 16Information about distance• Different sound levels•Frequency•Frequency– atmospheric perspective (vision)–The quality of sound (frequency) is modified by the q y ( q y) yatmosphere.• Movement parallax–The nearby sound moves quickly than the far away sound.•Direct sound vs. reflected soundDirect sound vs. reflected sound– Nearby sound tend to be direct, distant sound tends to be indirectch 12 17The physiological basis forThe physiological basis for localizationch 12 18• Interaural time difference detectors– E.g., a neuron that responds best when a sound reaches the left ear first and the right ear (vice g(versa) 1 millisecond later.ch 12 19Left Ear Right Earch 12 20The same timeLeft Ear Right Earch 12 21The same timeLeft Ear Right Earch 12 22Different timeLeft Ear Right Earch 12 23Different timeLeft Ear Right Earch 12 24Different timeLeft Ear Right Earch 12 25Different