1. HEARING

2. The Nature of Sound Sound, like light, comes in waves
Sound is vibration
Features of sound include:
Pitch
Hertz
Decibels

3. Pitch A sound’s highness or lowness
Dependent on the frequency of the sound wave
Is measured as hertz (Hz)
High pitched sounds
Low pitched sounds

4. Hertz (Hz)
A measure of the number of sound wave peaks per second; measures “frequency”
Determines the pitch of the sound
Human hearing goes from 20 Hz to 20,000 Hz

5. Frequency of Sound Waves
The frequency of a sound wave is measured as the number of cycles per second (Hertz)
20,000 Hz Highest Frequency we can hear
4,186 Hz Highest note on a piano
1,000 Hz Highest pitch of human voice
100 Hz Lowest pitch of human voice
27 Hz Lowest note on a piano

6. Decibel (dB) A measure of the height of the sound wave
Determines the loudness of the sound
Sometimes called amplitude
Loud sounds
Soft sounds

8. Above are examples of Frequency & Amplitude/decibels
Who hits the higher pitch? Christina or Mariah?
Discovering PSY p. 94 Figure 3.7
Above are examples of Frequency & Amplitude/decibels
Timbre – distinctive quality of a sound determined by the complexity of the wave and its different combinations of frequencies. (Figure C is more complex than Figures A or B)

9. The Structure of the Auditory System

10. Hearing: Sound Waves
Auditory perception occurs when sound waves interact with the structures of the ear
Audition (sense of hearing) results in sound waves being collected in the outer ear, amplified in the middle ear and converted to neural messages in the inner ear.

11. Purpose of the structures in the ear:
Anatomy of Ear
Purpose of the structures in the ear:
Measure the frequency (pitch) of sound waves
Measure the amplitude (loudness) of sound waves

12. Parts of the Ear – Sound Waves enter through the Pinna

13. Hearing: Sound Localization

14. 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?

15. Localization of Sound

16. Parts of the Ear – Auditory Canal

17. Auditory Canal
Sound Waves enter through the pinna then travel through the auditory canal.
The opening through which sound waves travel as they move into the ear for processing
Ends at the tympanic membrane (eardrum)

18. Parts of the Ear – Tympanic Membrane (Eardrum)

19. Tympanic Membrane (eardrum)
The tissue barrier that 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 - Ossicles

21. Ossicles
Three tiny bones that transfer sound waves from the eardrum to the cochlea
Hammer, anvil and stirrup
In old age they may become brittle or damaged resulting in conduction deafness

22. Parts of the Ear - Cochlea

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

24. Parts of the Ear – Oval Window

25. Oval Window
The point on the surface of the cochlea which receives the sound vibration from the ossicles
As the oval window vibrates, the fluid in the cochlea vibrates moving hair cells along the basilar membrane.

26. Hair cells along the Basilar Membrane move as the fluid vibrates

27. Anatomy of the Cochlea Another View
Outer ear
Middle ear
Inner ear
A sound causes
the basilar
membrane to wave
up and down.
Basilar
membrane
Hair cells
Tectorial
Round window
Eardrum
Oval window
Cochlea,
partially
uncoiled
Stirrup
Anvil
Hammer
Sound
waves
Auditory
canal

28. Hair Cells
The receptor cells for hearing in the cochlea that change sound vibrations into neural impulses. When they move they trigger action potential in the base of the hair cell (transduction).
Similar to the rods and cones within the eye except hair cells are sensitive to vibrations rather than light.
If these are damaged (due to prolonged loud noises) then you have nerve deafness which cannot be helped by a hearing aid.

29. Parts of the Ear – Auditory Nerve

30. Auditory Nerve
The nerve that carries sound information from the ears to the thalamus then to the auditory cortex in the temporal lobes of the brain
The auditory nerve is stimulated by the hair cells in the basilar membrane of the cochlea.

31. Major Divisions of the Ear
Outer Ear—acts as a funnel to direct sound waves towards inner structures
Middle Ear—consists of three small bones (or ossicles) that amplify the sound
Inner Ear—contains the structures that actually transduce sound into neural response

32. Divisions of the Ear

33. Divisions of the Ear

34. Divisions of the Ear

35. Anatomy of the Ear: A final look
Hockenbury Powerpoint (schulman)

36. Transduction of Sounds
Sound waves are captured by the Pinna and sent down the ear canal where they stimulate the eardrum.
The eardrum’s vibrations are amplified by the ossicles (hammer, anvil, stirrup).
These vibrate the oval window on the cochlea which in turn vibrates the fluid around the basilar membrane.
The fluid bends the hair cells on the basilar membrane triggering action potential in the base of the hair cells.
This message is transmitted to the auditory nerve which carries the info to the thalamus and then to the auditory cortex of the temporal lobe.
Review using this Nobel Prize site on Hearing

37. How Can I Remember This? Please – Pinna Eat – Ear Canal
Everything – Eardrum
Offered – Ossicles
On – Oval Window
Cuisine – Cochlea
Buffet – Basilar Membrane
Helpful – Hair Cells
Attendants – Auditory Nerve
Take – Thalamus
Away – Auditory Cortex
Trash – Temporal Lobe

38. Or Maybe This Works Better…
Portenga- [Pinna] evaluates- [ear canal] exams- [eardrum] on- [Ossicles] ominous- [oval window] charts- [cochlea] between- [basilar membrane] hungry- [Hair Cells] architects- [Auditory nerve] that- [Thalamus] always- [Auditory cortex] titter- [Temporal lobe]

39. Distinguishing Pitch
Frequency theory—basilar membrane vibrates at the same frequency as the sound wave/oval window
The higher the frequency wave the faster the firing of hair cells
Theory used to explain how you hear low frequencies
Place theory—different frequencies cause larger vibrations at different locations along the basilar membrane
Different pitches stimulate different areas on the basilar membrane
The brain receives these messages and interprets them as different pitches.
Theory used to explain how you hear high frequencies.
Use both theories when you listen to sounds with both high and low frequencies. See this website to see how it works.

40. Direction of traveling wave
Frequency Theory
The Basilar Membrane vibrates according to the same Frequency of the sound wave
Basilar
membrane
Distal
end
Proximal
Oval window
Direction of traveling wave

41. Place Theory: Different Frequencies stimulate different areas of the Basilar Membrane

42. Coding and Auditory Masking
The way in which waves travel down the Basilar Membrane causes some sounds to interfere with (or mask) our ability to hear other sounds
Low frequency sounds provide better masking than high frequency sounds

43. Auditory Masking
Piccolo, soft
Bassoon, loud
Piccolo, loud
Bassoon, soft
Distance along basilar membrane
(a)
(b)
Effect of bassoon on basilar membrane
Vibration
amplitude
of basilar
membrane
Effect of piccolo on basilar membrane
Low frequency sounds effectively mask high frequency sounds
High frequency sounds cannot effectively mask low frequency sounds
Hockenbury Powerpoint (schulman)