1. Jon Epp’s Office Hours: Tues 11-12 in EP1246 or by appointment jon.epp@uleth.ca

2. Sensory Systems: Hearing

3. What do we hear? Sound is a compression wave: When speaker is stationary, the air is uniformly dense Speaker Air Molecules

4. What do we hear? Sound is a compression wave: Speaker When the speaker moves, it compresses the air in front of it.

5. What do we hear? Sound is a compression wave: The speaker moves back leaving an area with less air behind - called rarefaction Compression Rarefaction

6. What do we hear? Sound is a compression wave: Speaker The speaker moves forward again starting the next wave Compression Rarefaction

7. What do we hear? Sound is a compression wave - it only “looks” like a wave if we plot air pressure against time Air Pressure Time

8. Properties of a Sound Wave 1. Amplitude: difference in air pressure between compression and rarefaction

9. Properties of a Sound Wave 1. Amplitude: difference in air pressure between compression and rarefaction –What is the perception that goes along with the sensation of sound amplitude?

10. Properties of a Sound Wave 1. Amplitude: difference in air pressure between compression and rarefaction –What is the perception that goes along with the sensation of sound amplitude? LOUDNESS

11. Properties of a Sound Wave 2. Frequency: how many regions of compression (or rarefaction) pass by a given point per second (expressed in Hertz)

12. Properties of a Sound Wave 2. Frequency: how many regions of compression (or rarefaction) pass by a given point per second (expressed in Hertz) –What is the perception that goes along with the sensation of frequency?

13. Properties of a Sound Wave 2. Frequency: how many regions of compression (or rarefaction) pass by a given point per second (expressed in Hertz) –What is the perception that goes along with the sensation of frequency? PITCH

14. Sensing Vibrations

15. Outer ear transmits and modifies sound (critical for sound localization)

16. Sensing Vibrations Middle ear turns compression waves into mechanical motion oval window stapes

17. Sensing Vibrations Middle ear turns compression waves into mechanical motion Ear Drum Oval window

18. Sensing Vibrations Middle ear turns compression waves into mechanical motion Ear Drum Oval window Compression Wave

19. Sensing Vibrations The cochlea, in the inner ear, is a curled up tube filled with fluid. Auditory Nerve to Brain

20. Sensing Vibrations Inside cochlea is the basilar membrane Movement of the oval window causes ripples on the basilar membrane

21. Sensing Vibrations Basilar membrane measures the amplitude and frequency of sound waves –amplitude (loudness) –frequency (pitch)

22. Sensing Vibrations Basilar membrane measures the amplitude and frequency of sound waves –amplitude (loudness) - magnitude of displacement of the basilar membrane –frequency (pitch)

23. Sensing Vibrations Basilar membrane measures the amplitude and frequency of sound waves –amplitude (loudness) - magnitude of displacement of the basilar membrane –frequency (pitch) - frequency and location of displacements of the basilar membrane

24. Sensing Vibrations Basilar membrane measures the amplitude and frequency of sound waves –frequency (pitch) - frequency and location of displacements of the basilar membrane

25. Sensing Vibrations Bundles of “hair cells” are embedded in basilar membrane

26. Sensing Vibrations When hair cells sway back and forth, they let ions inside This flow of charges is converted to action potentials and sent along the auditory pathway

27. The Auditory Pathway The auditory pathway is complex and involves several “stations” along the way to the auditory cortex in the brain Lots of processing must be done in real-time on auditory signals!

28. How Can You Localize Sound? Imagine digging two trenches in the sand beside a lake so that water can flow into them. Now imagine hanging a piece of cloth in the water in each trench. Your job is to determine the number and location and type of every fish, duck, person, boat, etc. simply by examining the motion of the cloth. That’s what your auditory system does!

29. How do we Stay Balanced? The Vestibular System

30. Vestibular System (Balance)

33. Head accelerates this way Cupula gets pushed Fluid goes this way

34. Vestibular System (Balance) Head accelerates this way Cupula gets pushed Fluid goes this way

35. Vestibular System (Balance) movement of the cupula is detected by hair cells hair cells in the vestibular system are more sensitive than hair cells on the basilar membrane!

36. Vestibular, Visual, and Proprioceptive Systems Work Together Try standing on one foot with your eyes closed!

37. Fun Facts about The Vestibular System Seasickness arises when the vestibular system and the visual system send conflicting information

38. Fun Facts about The Vestibular System Seasickness arises when the vestibular system and the visual system send conflicting information People can be knocked down by moving walls!

39. Fun Facts about The Vestibular System Seasickness arises when the vestibular system and the visual system send conflicting information People can be knocked down by moving walls! Alcohol causes the spins by (among other things) changing the density of the fluid in the semicircular canals

40. Next Time: Taste, Smell, Touch