Sensation9

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1. The physical stimulus for audition is the;
sound wave
2. Sounds are created when;
objects vibrate
3. Area of refractions-
when there is a lot of room between molecules
4. Compression
air molecules are compacted together
5. Less frequency waves=
lower sounds
6. Frequency
• Number of pressure changes per cycle
• Measured in hertz (Hz)
7. 1Hz =
one cycle per second
8. Pitch
Our perception of frequency
9. Amplitude
• Amount of change in pressure
• Also called intensity
• Measured in decibels (dB)
10. Loudness
Our perception of amplitude
11. Decibels
• measures the physical intensity of sound
• Logarithmic scale
12. Reletively small decibel changes can correspond to;
large physical changes
13. An increase in 6dB;
Doubles the amount of sound pressure
14. Typical threshold is;
1-2 dB
15. Complexity
• Number of different frequencies in a sound
• Physical
16. Fundamental
• lowest frequency
• Determines pitch
17. Harmonics
Higher pitched tones related to the fundamental (makes things sound good or bad)
18. Fourier Analysis and Hearing:
Any complex tone can be represented as a series of simple tones (sine waves)
19. Fundamental + 2nd harmonic + 3rd harmonic =
composite wave
20. Ohm's Law
Because the auditory system does a Fourier analysis on complex tones, we are aware of each of the simple tones
21. Timbre
Our perception of complexity
22. Timbre is created by the kind and number of;
overtones
23. Rich, full sounds (violin, voice) have;
many overtones or harmonics
24. Pure, thin sounds (flute) have;
few overtones
25. Phase
• The reletive position of two or more sine waves
• physical
• means where the wave is in compression - rare fraction cycle
26. In-phase:
Peaks occure at the same time (troughs)
27. Out of phase:
occur at different time
28. Noise Cancellation
• Destructive interference
• Sound waves can cancel each other out if they are 180 degrees out of phase
• Cars and cell phones are doing this
29. Resonant Frequency
• The frequency with which an object vibrates when hit
• Knocking on the body of a cello (strings start to vibrate)
30. Because of Resonant Frequency an object:
will begin to vibrate if a sound wave matching the object's resonant frequency travels close to the object = resonant
31. Pinna
The outer funnel-like part of the ear
32. Ear Canal
The canal that conducts sound vibrations from the pinnato the tympanic membrane and prevents damage to the tympanic membrane
33. Tympanic membrane
• The eardrum
• A thin sheet of skin at the end of the outer ear canal.
34. The tympanic membrane vibrates;
in response to sound
35. Outer ear
the external sound gathering portion of the ear, consisting of the pinna and the ear canal
36. Middle Ear
an air filled chamber containing the middle bones or ossicles
37. The middle ear conveys and amplifies
vibration from the tympanic membrane to the oval window
38. Ossicles
Three tiny bones of the middle ear; malleus, incus, and stapes
39. Malleus
• one of the ossicles
• Receives vibration from the tympanic mem. and is attached to the incus
40. Incus
• The middle ossicle
• Connects the malleus and stapes
41. Stapes
Connected to the incus on one end, the stapes presses against the oval window of the cochlea on the other end
42. Oval Window
The flexible opening to the cochlea through which the stapes transmits vibration to the fluid inside
43. Inner ear
A hollow cavity in the temporal bone of the skull and the structures within this cavity: the cochlea and vestibular canals
44. Tensor Tympani
the muscle attached to the malleus
45. Tensing the tensor tympani;
decreases vibration
46. Stapedius
• The muscle attached to the stapes
• tensing this muscle decreases vibration
47. Acoustic reflex
A reflex that protects the ear fromintense sounds, via contrasction of the stapedeus and tensor tympani muscles
48. Cochlea
A spiral structure of the inner ear containing the oran of corti
49. Tympanic Canal
• One of three fluid filled passages in the cochlea.
• It extends from the round window at the base o the cochlea to the helicotrema at the apex
• Also called scala tympani
50. Vestibular Canal
• one of three fluid filled passages in the cochlea
• Extends from the oval window to the helicotrama at the apex
• Scala Vestibula
51. Middle Canal
• One of three fluid filled passages in the cochlea
• Is sandwiched between the tympanic and vestibular canals and contains the cochlear partition
• Scala Media
52. Helicotrema
The opening that connects the tympanic and vestibular canals at the apex of the cochlea
53. Reissner's Membrane
A thin sheat of tissue separating the vestibular and middle canals in the cochlea
54. Basilar Membrane
A plate of fibers that forms the base of the cochlear partition and separates the middle and tympanic canals in the cochlea
55. Cochlear Partition
the combines basilar membrane, tectorial membrane, and organ of corti, which are together responsible for the transduction of sound waves into neural signals
56. On top of the Basilar mem. is the
organ of corti
57. Hair Cells
• Transduce mechanical movement in the cochlea in to neural activity
• 3500 inner cells and 10,500 outer hair cells
58. 95% of auditory nerve cells connect with;
inner hair cells
59. Inner hair cells are;
Afferent (sending)
60. Outer hair cells are;
Efferent (receiving)
61. Function of Outer hair cells
• Sharpen information sent by inner cells (receive info. about which frequencies need to be heightened or amplified)
• Amplifies sounds
62. Otoacoustic Emissions
• Sound produced just by your ear, nothing else.
• Can be used to test newborn's hearing
63. Hair cells are tuned to specific frequencies called;
Tonotopically organized
64. Place Theory
• Hair cells are tonotopically organized on basilar membrane
• Low frequencies cause maximal displacement furthest from the oval window (apex)
• High frequencies cause max displacement closest to oval window (base)
65. How he determined place theory
he got cochlea from fresh cadavers and cut windows in it, played tones to see if basilar mem. moved - high frequencies
66. Place Theory has to do with;
intensity
67. The lower the sound,
the less likely it will be to be a crisp sound
68. Problem with place theory
dont see nice neat traveling waves for low frequency sounds
69. Temporal Code theory mainly deals with;
Time
70. Temporal Code theory
Frequency of sound is coded by how many times auditory neurons fire
71. Phase locking
Firing of a single neuron at one distinct point in the cycle of a sound wave
72. Problem with Temporal Code Theory
• There arent enough hair cells to be tuned for all frequencies
• Nerve cells can only fire up to 1000 times
73. Solution to Temporal code theory
• Cells work in groups to code frequency
• Look at total output of group of cells to determine frequency of sound
74. Temporal Theory summary
• Frequency coded by the sum of action potentials produced by a group of cells
• Amplitude coded by determining how many cells in that group are firing at the same time
• The more cells firing means the louder the sound
75. Cooperation of Place and Temporal Code theory
• High frequencies: place theory (above 3000Hz)
• Low frequencies: temp. theory (below 1000 Hz)
• Between 1000 and 3000 Hz: both theories work
• Both theories say the same thing about amplitude
76. Threshold Tuning Curve
A map plotting the thresholds of a neuron or fiber in response to sine waves with varying frequencies at the lowest intensity that will give rise to a response
77. Volley principle
An idea stating that multiple neurons can provide a temporal code for frequency if each neuron fires at a distinct point in the period of a sound wave but doesnt fire on every period
78. Cochlear Nucleus
the first brain stem nucleus at which afferent auditory nerve fibers synapse
79. Superior Olive
an early brain stem region in the auditory pathway where inputs from both ears converge
80. Medial Geniculate Nucleus
the part of the thalamus that relays auditory signals to the temporal cortex and receives input from the auditory cortex
81. Tonotopic Organization
an arrangement in which neurons that respond to different frequencies are organized anatomically in order of frequency
82. Conductive hearing loss
hearing loss caused by problems with the bones of the middle ear
83. Otitis Media
inflammation of the middle ear, commonly in children as a result of infection
84. Otosclerosis
abnormal growth of the middle ear bones that causes hearing loss
85. Ototoxic
producing adverse effects on organs or nerves ivolved in hearing or balance
 Author: faulkebr ID: 116846 Card Set: Sensation9 Updated: 2011-11-15 15:35:38 Tags: Hearing Folders: Description: Chapter9 Show Answers: