1. Sound Waves Sound is created when objects vibrate. This vibration causes molecules in the surrounding medium to vibrate as well. This, in turn, causes pressure changes in the medium. Pressure Fluctuations Pattern stays the same Pressure decreases

2. Quantifying Sound Amplitude Intensity Frequency Hertz (Hz)

3. Most Sound is a Mix of Waves Time (msec)

4. Spectral Analysis

5. Differences in Animal Hearing

6. Differences in Mammalian Hearing

7. The Range of Human Hearing

8. Loudness Variations

9. Outer Ear Variations

10. Human Ear Divisions

11. Human Ear Anatomy

12. Middle Ear Bones Malleus Incus Stapes

13. Inner Ear - Cochlea

14. Cochlea Cross Section

15. Cochlear Partition Organ of Corti

16. Hair Cells

17. Hair Cell Neurochemistry Inner Hair Cells: afferent: Glu efferent: ACh Outer Hair Cells: afferent: ACh efferent: GABA

18. Sound, Vibration, and Transduction

19. Stereocilia Electronmicrograph of stereocilia tip links (Hudspeth, 1992)

20. Tip Link Neurochemistry Tip Link Movement: Opens non-selective ion channels K + and Ca ++ enter cell causing depolarization Causing voltage-gated Ca ++ channels to open at cells base Ca ++ triggers the release of neurotransmitter that stimulates afferent fiber

21. Cochlea Specific movement of the basilar membrane stimulates specific cells

22. Auditory Pathway Auditory Cortex Medial Geniculate Nucleus (MGN) Inferior Colliculus Superior Olivary Nucleus Cochlear Nucleus Auditory Nerve