1. Hearing: How do we hear?

2. Hearing: The Nature of Sound
Module 9: Sensation

3. Sound Sound, like light, comes in waves Sound is vibration
Features of sound include:
Pitch
Hertz
decibels

4. Pitch A sound’s highness or lowness
Dependent on the frequency of the sound wave – the more “waves per second” the higher the frequency or pitch
Is measured as hertz (Hz)

5. Hertz (Hz)
A measure of the number of sound wave peaks per second; measures “frequency”
Determines the pitch of the sound
One Hertz = one vibration per second

6. Low Pitch Wave peaks are far apart
Human hearing goes from 20 Hz to 20,000 Hz although some ears (and speakers) are better than others

7. High Pitch As pitch increases, so do the number of waves
Remember - Human hearing goes from 20 Hz to 20,000 Hz note: a kilohertz is 1,000 hertz so 20 kilohertz equals 20,000 hertz

8. Decibel (dB) A measure of the height of the sound wave
Determines the loudness of the sound
Sometimes called amplitude

9. What are good sounds versus bad
What volume do you think is okay?
Not good, not bad?
Bad?

11. Hearing: The Structure of the Auditory System
Module 9: Sensation

12. Break It Down
Sound waves are collected in the outer ear, amplified in the middle ear, and transduced, in the inner ear.

13. The visible part of the outer ear.
PINNA
The visible part of the outer ear.
It collects sound and directs it into the outer ear canal.

14. Parts of the Ear – Sound Waves

15. The opening through which sound waves travel as they move into the ear for processing
Ends at the eardrum
Auditory Canal

16. Parts of the Ear – Auditory Canal

17. THE MIDDLE EAR

18. Eardrum
Also called the tympanic membrane. A thin membrane that vibrates when sound waves reach it.
it transfers sound vibration from the air to the tiny bones of the middle ear
Can be damaged by objects in the ear or exceptionally loud noises

20. Parts of the Ear – Tympanic Membrane

21. Bones of the middle ear - Ossicles
Three tiny bones that transfer sound waves from the eardrum to the cochlea
Hammer, anvil and stirrup
Fun fact: the stirrup is the smallest bone in the human body – only .25 cm

23. Parts of the Ear - Occicles

24. Oval Window
The point on the surface of the cochlea which receives the sound vibration from the bones of the middle ear (ossicles)
As the oval window vibrates, the fluid in the cochlea vibrates.

25. Parts of the Ear – Oval Window

26. Cochlea
A hearing organ where sound waves are changed into neural impulses (transduction)
The major organ of hearing
Filled with fluid; a snail shaped body tube

27. Parts of the Ear - Cochlea

29. Hair Cells
The receptor cells for hearing in the cochlea that change sound vibrations into neural impulses
Transduction!

30. Parts of the Ear - Hair Cells

31. Parts of the Ear – Oval Window

32. Auditory Nerve
The nerve that carries sound information from the ears to the temporal lobes of the brain

33. Parts of the Ear – Auditory Nerve

34. Divisions of the Ear Ear’s structure can be divided into:
The outer ear
The middle ear
The inner ear

35. Divisions of the Ear

36. Divisions of the Ear

37. Divisions of the Ear

38. The Ossicles amplify the vibration of the eardrum
REVIEW
Hammer
Anvil
Stirrup
Ear Drum
The Ossicles amplify the vibration of the eardrum

39. Movement of the fluid causes the hair cells to move which causes TRANSDUCTION!

40. REVIEW Sound comes into the ear
Goes through the ear canal to the eardrum
Ear drum changes sound into vibrations
Vibrations go through middle ear to the inner ear –

41. REVIEW
Where vibrations are changed into neural impulses so that the brain can read / interpret the sound –
What are the receptors cells for hearing?

42. Problems with hearing Conduction deafness* (middle ear damage)
Nerve deafness (hair cell or auditory nerve damage)

43. Hearing: Sound Localization
Module 9: Sensation

44. Localization of Sound Locating where sound is originating from
Done through two cues:
Which ear hears the sound first?
Which ear hears the louder sound?

45. Localization of Sound

46. Another sense in your ears?
Is there another sense in your ear?

47. Vestibular Sense The system for sensing body orientation and balance
Relies on fluid in the semicircular canals of the inner ear
Spinning in circles disrupts the fluid.

48. Parts of the Ear – Semicircular Canals

49. Parts of the Ear – Semicircular Canals

50. Semicircular canal
What situations will affect the semicircular canal

51. EUSTACHIAN TUBE
A tube that connects the middle ear to the back of the nose; it equalizes the pressure between the middle ear and the air outside. When you "pop" your ears as you change altitude (going up a mountain or in an airplane), you are equalizing the air pressure in your middle ear.