Chapter 9: Hearing I Flashcards

1
Q

Describe the two basic qualities of sound: frequency and amplitude.

A
  • Frequency (for sound) is the number of times per second that a pattern of pressure change repeats. Frequency is perceived as pitch.
  • Amplitude (or intensity) The magnitude of displacement (increase or decrease) of a sound pressure wave.
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2
Q

How is amplitude associated with loudness?

A

Amplitude is perceived as loudness.

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3
Q

What is a sine wave and why is it important in studying auditory perception?

A

A sine wave is a waveform for which variation as function of time is a sine function. It is important to studying auditory perception because it is a pure tone, and the shape of sound waves.

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4
Q

Describe the concept of timbre

A

Timbre is the psychological sensation by which a listener can judge that two sounds with the same loudness and pitch are dissimilar. Timbre quality is conveyed by harmonics and other high frequencies

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5
Q

How is Sound Created

A

Sound is created by motions and vibrations of objects in the environment. The nature of these motions is determined by forces impinging on the objects and their resonance characteristics.

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6
Q

What are the roles of the ear canal?

A

The ear canal’s length and shape enhance sound frequencies between about 2000 and 6000 HZ, but the main purpose is to protect the tympanic membrane.

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7
Q

Describe the three tiny bones in the middle ear.

A

The three tiny bones in the ear (or the ossicles) are the malleus, incus and stapes. The malleus receives vibrations from the tympanic membrane and is attached to the incus. The incus connects the malleus to the stapes. The stapes presses against the oval window of the cochlea.

The ossicles amplify sound in two ways. 1.) their joints are hinged in such a way that the work like levers: a modest amount of energy becomes larger on the other. This lever action increases the amount of pressure change by about a third. 2.)They also increase the energy transmitted to the inner ear by concentrating energy fro a larger to a smaller surface area: the tympanic membrane, which moves the malleus about 18 times as large as the oval window, moved by the stapes.

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8
Q

Why can’t the acoustic reflex help protect the ear from abrupt loud sounds, such as gun fire?

A

The acoustic reflex (controlled by the tensor tympani and the stapedius) follows the onset of loud sounds by 1/5 of a second. It is not fast enough to muffle sounds as fast as a gun firing.

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9
Q

What is the function of the cochlea?

A

The cochlea translates the information carried by sound waves into neural signals. The tiny coiled structure allows vibrations pushed and pulled through the oval window to create waves o pressure changes to flow through the fluid of the vestibular canal. The displacement travels from the base of the cochlea, to its apex, to be interpreted by the organ of Corti.

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10
Q

Describe how the release of neurotransmitters results from the deflection of stereocilia.

A

Deflection of a hair cell’s stereocilia causes a change in voltage potential that initiate the release of neurotransmitters, which in turn encourages firing by auditory nerve fibers that have dendritic synapes on hair cells.

When a sterocilium deflects the tip link pulls on a larger stereocilium in a way that opens an ion pore somewhat like opening a small gate for a short period of time. This action permits K+ ions to flow rapidly into the hair cell, causing rapid depolarization. This depolarization leads to a rapid influx of Ca2+ (calcium ions) and initiation of the release of neurotransmitters from the base of the hair cell to stimulate dendrite of the auditory nerve.

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11
Q

How is place code related to tuning?

A

Different parts of the cochlea relate to different frequencies in the cochlea. This tuning is known as “place code” for sound frequency. It is caused by the way the structure of the basilar membrane changes along the length of the cochlea. The cochlea as a whole narrows from base to apex, but the basilar membrane actually widens toward the apex. In addition, the basilar membrane is thick at the base and becomes thinner as it widens. As a result, the cochlea separates frequencies along its length like an acoustic prism. Higher frequencies bend the narrower, stiffer regions of the basilar membrane more, and the lower frequencies cause greater displacements in the wider, more flexible regions near the apex.

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12
Q

How are inner hair cells different from outer hair cells?

A

Over 90% of the afferent fibers in the auditory nerve– fibers that information to the brain–synapse on the 3500 inner hair cells (10-30 auditory nerve fibers listen to one inner hair cell).
The outer hair cells serve a more mechanical role. Most of the nerve fibers that synapse with the outer hair celss are efferent fibers, conveying information FROM the brain. When these efferent fibers become active, outer hair cells that are connected to these fibers become longer and this makes the nearby cochlear partition stiffer that other parts, making the cochlea more sensitive and more sharply tuned to particular frequency.

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13
Q

What is the threshold tuning curve?

A

The threshold tuning curve is a graph 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.

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14
Q

What happens during two-tone suppression?

A

There is a decrease in the firing rate of one auditory nerve fiber due to one tone, when a second tone is presented at the same time.The suppression effect appears to be caused by mechanical changes to the basilar membrane.

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15
Q

What does an isointensity curve show us?

A

An isointensity curve is a map plotting the firing rate of an auditory nerve fiber against varying frequencies at a steady intensity.

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16
Q

What is rate saturation?

A

Rate saturation is the point at which a nerve fiber is firing as rapidly as possible and further stimulation is incapable of increasing the firing rate.

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17
Q

Why does phase locking occur?

A

Phase locking (firing of a single neuron at one distinct point in the cycle of a sound wave at a given frequency) may occur because AN fibers fire when the sterocilia of hair cells move in one directions but do not fire when the sterocilia move in the other direction. This carries a temporal code for the sound wave frequency.

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18
Q

Describe the volley principle.

A

The volley principle is the idea that multiple neurons can provide a temporal code for frequency if each neuron fires at a distinct point in a period of a sound wave, but does not fire fire on every period. Multiple AN fibers together can provide a temporal for frequency if different neurons each fire at different period of the sine wave.

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19
Q

What kind of organization exists in the primary auditory cortex (A1)?

A

Tonotopic organization. Neurons from A1 project to the surrounding belt area of cortex, and neurons from this belt synapse with neurons in the adjacent parabelt area. Just about any sound will cause activation in some part of A1. Processing proceeds from simpler to more complex stimuli as we move farther along the auditory pathway.

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20
Q

What is psychoacoustics?

A

Psychoacoustics is the study of the psychological correlates of the physical dimensions of acoustics; a branch of psychophysics.

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21
Q

What is the audibility threshold?

A

the audibility threshold is the lowest sound pressure level that can be reliably detected at a given frequency

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22
Q

What is white noise and when is it used?

A

White noise is noise consisting of all audible frequencies in equal amounts. White noise in hearing is analogous to white light in vision, for which all wave lengths are present.

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23
Q

Describe two kinds of hearing loss.

A

Otitis media-inflammation of the middle ear, commonly in children as a result of infection
Otosclerosis-Abnormal growth of the middle-ear bones that causes hearing loss.

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24
Q

acoustic reflex

A

A reflex that protects the ear from intense sounds, via contraction of the stapedius and tensor tympani muscles.

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25
Q

afferent fiber

A

A neuron that carries sensory information to the central nervous system.

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26
Q

amplitude or intensity

A

The magnitude of displacement (increase or decrease) of a sound pressure wave. Amplitude is perceived as loudness.

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27
Q

auditory nerve fiber

A

A collection of neurons that convey information from hair cells in the cochlea to (afferent) and from (efferent) the brain stem.

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28
Q

basilar membrane

A

A plate of fibers that forms the base of the cochlear partition and separates the middle and tympanic canals in the cochlea.

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29
Q

belt area

A

A region of cortex, directly adjacent to the primary auditory cortex (A1), with inputs from A1, where neurons respond to more complex characteristics of sounds.

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30
Q

characteristic frequency (CF)

A

The frequency to which a particular auditory nerve fiber is most sensitive.

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31
Q

cochlea

A

A spiral structure of the inner ear containing the organ of Corti.

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32
Q

cochlear nucleus

A

The first brain stem nucleus at which afferent auditory nerve fibers synapse.

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33
Q

cochlear partition

A

The combined basilar membrane, tectorial membrane, and organ of Corti, which are together responsible for the transduction of sound waves into neural signals.

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34
Q

conductive hearing loss

A

Hearing loss caused by problems with the bones of the middle ear.

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35
Q

critical bandwidth

A

The range of frequencies conveyed within a channel in the auditory system.

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36
Q

decibel (dB)

A

A unit of measure for the physical intensity of sound. Decibels define the difference between two sounds as the ratio between two sound pressures. Each 10:1 sound pressure ratio equals 20 dB, and a 100:1 ratio equals 40 dB.

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37
Q

ear canal

A

The canal that conducts sound vibrations from the pinna to the tympanic membrane and prevents damage to the tympanic membrane.

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38
Q

efferent fiber

A

A neuron that carries information from the central nervous system to the periphery.

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39
Q

equal-loudness curve

A

A graph plotting sound pressure level (dB SPL) against the frequency for which a listener perceives constant loudness.

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40
Q

frequency

A

For sound, the number of times per second that a pattern of pressure change repeats. Frequency is perceived as pitch.

41
Q

fundamental frequency

A

The lowest-frequency component of a complex periodic sound.

42
Q

hair cell

A

Any cell that has stereocilia for transducing mechanical movement in the inner ear into neural activity sent to the brain; some hair cells also receive inputs from the brain.

43
Q

harmonic spectrum

A

The spectrum of a complex sound in which energy is at integer multiples of the fundamental frequency.

44
Q

helicotrema

A

The opening that connects the tympanic and vestibular canals at the apex of the cochlea.

45
Q

hertz (Hz)

A

A unit of measure for frequency. One hertz equals one cycle per second.

46
Q

high-spontaneous fiber

A

An auditory nerve fiber that has a high rate (more than 30 spikes per second) of spontaneous firing; high-spontaneous fibers increase their firing rate in response to relatively low levels of sound.

47
Q

incus

A

The middle of the three ossicles, connecting the malleus and the stapes.

48
Q

inferior colliculus

A

A midbrain nucleus in the auditory pathway.

49
Q

inner ear

A

A hollow cavity in the temporal bone of the skull, and the structures within this cavity: the cochlea and the semicircular canals of the vestibular system.

50
Q

isointensity curve

A

A map plotting the firing rate of an auditory nerve fiber against varying frequencies at a steady intensity.

51
Q

loudness

A

The psychological aspect of sound related to perceived intensity (amplitude).

52
Q

low-spontaneous fiber

A

An auditory nerve fiber that has a low rate (less than 10 spikes per second) of spontaneous firing; low-spontaneous fibers require relatively intense sound before they will fire at higher rates.

53
Q

malleus

A

One of the three ossicles. The malleus receives vibration from the tympanic membrane and is attached to the incus.

54
Q

masking

A

Using a second sound, frequently noise, to make the detection of another sound more difficult.

55
Q

medial geniculate nucleus

A

The part of the thalamus that relays auditory signals to the temporal cortex and receives input from the auditory cortex.

56
Q

mid-spontaneous fiber

A

An auditory nerve fiber that has a medium rate (10–30 spikes per second) of spontaneous firing. The characteristics of mid-spontaneous fibers are intermediate between low- and high-spontaneous fibers.

57
Q

middle canal

A

One of three fluid-filled passages in the cochlea. The middle canal is sandwiched between the tympanic and vestibular canals and contains the cochlear partition. Also called scala media.

58
Q

middle ear

A

An air-filled chamber containing the middle bones, or ossicles. The middle ear conveys and amplifies vibration from the tympanic membrane to the oval window.

59
Q

organ of Corti

A

A structure on the basilar membrane of the cochlea that is composed of hair cells and dendrites of auditory nerve fibers.

60
Q

ossicle

A

Any of three tiny bones of the middle ear: malleus, incus, and stapes.

61
Q

otitis media

A

Inflammation of the middle ear, commonly in children as a result of infection.

62
Q

otosclerosis

A

Abnormal growth of the middle-ear bones that causes hearing loss.

63
Q

ototoxic

A

Producing adverse effects on cochlear or vestibular organs or nerves.

64
Q

outer ear

A

The external sound-gathering portion of the ear, consisting of the pinna and the ear canal.

65
Q

oval window

A

The flexible opening to the cochlea through which the stapes transmits vibration to the fluid inside.

66
Q

parabelt area

A

A region of cortex, lateral and adjacent to the belt area, where neurons respond to more complex characteristics of sounds, as well as to input from other senses.

67
Q

phase locking

A

Firing of a single neuron at one distinct point in the period (cycle) of a sound wave at a given frequency. (The neuron need not fire on every cycle, but each firing will occur at the same point in the cycle.)

68
Q

pinna

A

The outer, funnel-like part of the ear.

69
Q

pitch

A

The psychological aspect of sound related mainly to perceived frequency.

70
Q

place code

A

Tuning of different parts of the cochlea to different frequencies, in which information about the particular frequency of an incoming sound wave is coded by the place along the cochlear partition that has the greatest mechanical displacement.

71
Q

primary auditory cortex (A1)

A

The first area within the temporal lobes of the brain responsible for processing acoustic information.

72
Q

psychoacoustics

A

The study of the psychological correlates of the physical dimensions of acoustics; a branch of psychophysics.

73
Q

rate saturation

A

The point at which a nerve fiber is firing as rapidly as possible and further stimulation is incapable of increasing the firing rate.

74
Q

rate-intensity function

A

A graph plotting the firing rate of an auditory nerve fiber in response to a sound of constant frequency at increasing intensities.

75
Q

Reissner’s membrane

A

A thin sheath of tissue separating the vestibular and middle canals in the cochlea.

76
Q

round window

A

A soft area of tissue at the base of the tympanic canal that releases excess pressure remaining from extremely intense sounds.

77
Q

sensorineural hearing loss

A

Hearing loss due to defects in the cochlea or auditory nerve.

78
Q

sine wave or pure tone

A

A waveform for which variation as a function of time is a sine function.

79
Q

spectrum

A

A representation of the relative energy (intensity) present at each frequency.

80
Q

stapedius

A

The muscle attached to the stapes; tensing the stapedius decreases vibration.

81
Q

stapes

A

One of the three ossicles. Connected to the incus on one end, the stapes presses against the oval window of the cochlea on the other end.

82
Q

stereocilium

A

Any of the hairlike extensions on the tips of hair cells in the cochlea that, when flexed, initiate the release of neurotransmitters.

83
Q

superior olive

A

An early brain stem region in the auditory pathway where inputs from both ears converge.

84
Q

tectorial membrane

A

A gelatinous structure, attached on one end, that extends into the middle canal of the ear, floating above inner hair cells and touching outer hair cells.

85
Q

temporal code

A

Tuning of different parts of the cochlea to different frequencies, in which information about the particular frequency of an incoming sound wave is coded by the timing of neural firing as it relates to the period of the sound.

86
Q

temporal integration

A

The process by which a sound at a constant level is perceived as being louder when it is of greater duration. The term also applies to perceived brightness, which depends on the duration of light.

87
Q

tensor tympani

A

The muscle attached to the malleus; tensing the tensor tympani decreases vibration.

88
Q

threshold tuning curve

A

A graph 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.

89
Q

timbre

A

The psychological sensation by which a listener can judge that two sounds with the same loudness and pitch are dissimilar. Timbre quality is conveyed by harmonics and other high frequencies.

90
Q

tip link

A

A tiny filament that stretches from the tip of a stereocilium to the side of its neighbor.

91
Q

tonotopic organization

A

An arrangement in which neurons that respond to different frequencies are organized anatomically in order of frequency.

92
Q

two-tone suppression

A

A decrease in the firing rate of one auditory nerve fiber due to one tone, when a second tone is presented at the same time.

93
Q

tympanic canal

A

One of three fluid-filled passages in the cochlea. The tympanic canal extends from the round window at the base of the cochlea to the helicotrema at the apex. Also called scala tympani.

94
Q

tympanic membrane

A

The eardrum; a thin sheet of skin at the end of the outer ear canal. The tympanic membrane vibrates in response to sound.

95
Q

vestibular canal

A

One of three fluid-filled passages in the cochlea. The vestibular canal extends from the oval window at the base of the cochlea to the helicotrema at the apex. Also called scala vestibuli.

96
Q

volley principle

A

The idea 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 does not fire on every period.

97
Q

white noise

A

Noise consisting of all audible frequencies in equal amounts. White noise in hearing is analogous to white light in vision, for which all wavelengths are present.

98
Q

Formula for Pure Tone

A

p(t)= Asin (2πƒt+ø) p (mean pressure)

99
Q

Decible System

A

It is a logarithmic scale. 20db = 10 squared more sound than one that 10 db,