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Hearing in the Environment 1

Hearing in the Environment 1. PSY 295 – Sensation & Perception Christopher DiMattina , PhD. Sound localization. The problem of auditory localization. In vision, it is easy to tell where something is in space by its position on the retina C ochlea is organized by frequency rather than space

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Hearing in the Environment 1

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  1. Hearing in the Environment 1 PSY 295 – Sensation & Perception Christopher DiMattina, PhD

  2. Sound localization PSY 295 - Grinnell College - Fall 2012

  3. The problem of auditory localization • In vision, it is easy to tell where something is in space by its position on the retina • Cochlea is organized by frequency rather than space • Sound location must be computed by the brain PSY 295 - Grinnell College - Fall 2012

  4. Problem of sound localization PSY 295 - Grinnell College - Fall 2012

  5. Planes of localization PSY 295 - Grinnell College - Fall 2012

  6. Cues for azimuthal localization PSY 295 - Grinnell College - Fall 2012

  7. Cues for horizontal plane • Sounds travel different distances to get to two ears • Sounds are louder in closer ear PSY 295 - Grinnell College - Fall 2012

  8. Cues for horizontal plane • High frequencies are attenuated by head • Low frequencies travel around head and are not attenuated PSY 295 - Grinnell College - Fall 2012

  9. Question • Which frequencies would have stronger cue for loudness difference (inter-aural level difference – ILD)? • Which frequencies would have stronger cue for time or phase differences (inter-aural time difference)? PSY 295 - Grinnell College - Fall 2012

  10. Duplex theory PSY 295 - Grinnell College - Fall 2012

  11. Interaural Level Differences PSY 295 - Grinnell College - Fall 2012

  12. ILD ineffective at low frequencies PSY 295 - Grinnell College - Fall 2012

  13. ILD effective at high frequencies PSY 295 - Grinnell College - Fall 2012

  14. Interaural timing differences • Sound takes longer to reach one ear than the other PSY 295 - Grinnell College - Fall 2012

  15. ITD for head positions • Largest ITD is 0.64 milliseconds PSY 295 - Grinnell College - Fall 2012

  16. ITD PSY 295 - Grinnell College - Fall 2012

  17. ILD + ITD are not entirely sufficient • Cone of confusion PSY 295 - Grinnell College - Fall 2012

  18. Head movements help PSY 295 - Grinnell College - Fall 2012

  19. Computing ITD & ILD in the Brain PSY 295 - Grinnell College - Fall 2012

  20. Auditory Brainstem Nuclei • Lateral Superior Olive (LSO) • Medial Superior Olive (MSO) • One synapse from cochlear nucleus PSY 295 - Grinnell College - Fall 2012

  21. Auditory Brainstem Nuclei • MSO – inter-aural time differences (ITD) • LSO – inter-aural level differences (ILD) PSY 295 - Grinnell College - Fall 2012

  22. LSO codes IID PSY 295 - Grinnell College - Fall 2012

  23. Neural circuit in brain slice PSY 295 - Grinnell College - Fall 2012

  24. Neural circuit PSY 295 - Grinnell College - Fall 2012

  25. MSO codes ITD PSY 295 - Grinnell College - Fall 2012

  26. Jeffress model PSY 295 - Grinnell College - Fall 2012

  27. Cool animation • http://mustelid.physiol.ox.ac.uk/drupal/?q=topics/jeffress-model-animation PSY 295 - Grinnell College - Fall 2012

  28. Anatomical evidence PSY 295 - Grinnell College - Fall 2012

  29. Localization in 3-D PSY 295 - Grinnell College - Fall 2012

  30. How do we localize in elevation? PSY 295 - Grinnell College - Fall 2012

  31. Pinna PSY 295 - Grinnell College - Fall 2012

  32. Pinna filters sounds PSY 295 - Grinnell College - Fall 2012

  33. Notch location varies with elevation PSY 295 - Grinnell College - Fall 2012

  34. Spectral elevation cues PSY 295 - Grinnell College - Fall 2012

  35. Neurons tuned for spectral notches • Neurons in the inferior colliculus and dorsal cochlear nucleus exhibit tuning for spectral notches PSY 295 - Grinnell College - Fall 2012

  36. Different solution in barn owls • One ear points up, the other points down • ILD provides a cue for elevation PSY 295 - Grinnell College - Fall 2012

  37. Map of auditory space • The barn owl homologue of the inferior colliculus has a topographical map of auditory space • Mammalian IC does not have such a neat map PSY 295 - Grinnell College - Fall 2012

  38. Cues for distance • How do we tell the distance of sounds? • Loudness – distance confound • Analogous to problem of depth perception in vision PSY 295 - Grinnell College - Fall 2012

  39. Cues for distance • Movement can help (analogous to motion parallax) • Greater attenuation of high frequencies with distance (analogous to aerial haze) PSY 295 - Grinnell College - Fall 2012

  40. Reverberation • Nearby sounds take more direct path • Far away sounds bounce off things PSY 295 - Grinnell College - Fall 2012

  41. Acknowledgements • Many figures taken from the following websites • David Heeger @ NYU • Center for Hearing Science @ JHU PSY 295 - Grinnell College - Fall 2012

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