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PSYCH 367 > Topic 11: Hearing > Flashcards

Topic 11: Hearing Flashcards

1
Q

Sound

A

the perceptual experience of hearing

the statement “I hear a sound” is using sound in this sense

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2
Q

Sound Wave

A

pattern of pressure changes in a medium

most of the sounds we hear are due to pressure changes in the air, although sound can be transmitted through water and solids as well

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3
Q

Pure Tone

A

a tone with pressure changes that can be described by a single sine wave

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4
Q

Frequency

A

the number of times per second that pressure changes of a sound stimulus repeat

is measured in Hertz, where 1 Hertz is one cycle per second

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5
Q

Amplitude

A

in the case of a repeating sound wave, such as the sine wave of a pure tone, amplitude represents the pressure difference between atmospheric pressure and the maximum pressure of the wave

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6
Q

Hertz (Hz)

A

the unit for designating the frequency of a tone

1 Hertz equals one cycle per second

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7
Q

Decibel (dB)

A

a unit that indicates the pressure of a sound stimulus relative to a reference pressure: dB = 20log(p/po), where p is the pressure of the tone and po is the reference pressure

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8
Q

Sound Pressure Level

A

a designation used to indicate that the reference pressure used for calculating a tone’s decibel rating is set at 20 micropascals, near the threshold in the most sensitive frequency range for hearing

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9
Q

Level

A

short for sound pressure level or sound level

indicates the decibels or sound pressure of a sound stimulus

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10
Q

Sound Level

A

the pressure of a sound stimulus, expressed in decibels

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11
Q

Periodic Waveform

A

for the stimulus for hearing, a pattern of repeating pressure changes

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12
Q

Fundamental Frequency

A

the first harmonic of a complex tone

usually the lowest frequency in the frequency spectrum of a complex tone

the tone’s other components, called higher harmonics, have frequencies that are multiples of the fundamental frequency

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13
Q

Harmonic

A

pure-tone components of a complex tone that have frequencies that are multiples of the fundamental frequency

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14
Q

Fundamental

A

a pure tone with frequency equal to the fundamental frequency of a complex tone

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15
Q

Higher Harmonics

A

pure tones with frequencies that are whole number (2, 3, 4, etc.) multiples of the fundamental frequencies

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16
Q

Frequency Spectra

A

a plot that indicates the amplitudes of the various harmonics that make up a complex tone

each harmonic is indicated by a line that is positioned along the frequency axis, with the height of the line indicating the amplitude of the harmonic

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17
Q

Loudness

A

the quality of sound that ranges from soft to loud

for a tone of a particular frequency, loudness usually increases with increasing decibels

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18
Q

Audibility Curve

A

a curve that indicates the sound pressure level (SPL) at threshold for frequencies across the audible system

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19
Q

Auditory Response Area

A

the psychophysically measured area that defines the frequencies and sound pressure levels over which hearing frequencies and sound pressure levels over which hearing functions

this area extends between the audibility curve and the curve for the threshold of feeling

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20
Q

Equal Loudness Curves

A

a curve that indicates the sound pressure levels that result in a perception of the same loudness at frequencies across the audible spectrum

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21
Q

Pitch

A

the quality of sound, ranging from low to high, that is most closely associated with the frequency of a tone

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22
Q

Tone Height

A

the increase in pitch that occurs as frequency is increased

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23
Q

Tone Chroma

A

the perceptual similarity of notes separated by one or more octaves

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24
Q

Octave

A

tones that have frequencies that are binary multiples of each other (2, 4, etc.)

for example, an 800-Hz tone is one octave above a 400-Hz tone

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25
Q

Effect of the Missing Fundamental

A

removing the fundamental frequency and other lower harmonies from a musical tone do not change the tone’s pitch

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26
Q

Timbre

A

the quality that distinguishes between two tones that sound different even though they have the same loudness, pitch, and duration

differences in timbre are illustrated by the sounds make by different musical instruments

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27
Q

Attack

A

the buildup of sound energy that occurs at the beginning of a tone

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28
Q

Decay

A

the decrease in the sound signal that occurs at the end of a tone

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29
Q

Periodic Sounds

A

a sound stimulus in which the pattern of pressure changes repeats

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30
Q

Aperiodic Sounds

A

sound waves that do not repeat

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31
Q

Outer Ear

A

the pinna and the auditory canal

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32
Q

Pinnae

A

the part of the ear that is visible on the outside of the head

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33
Q

Auditory Canal

A

the canal through which air vibrations travel from the environment to the tympanic membrane

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34
Q

Tympanic Membrane

A

a membrane at the end of the auditory canal that vibrates in response to vibrations of the air and transmits these vibrations to the ossicles in the middle ear

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35
Q

Eardrum

A

another term for the tympanic membrane, the membrane located at the end of the auditory canal that vibrates in response to pressure changes

this vibration is transmitted to the bones of the middle ear

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36
Q

Resonance

A

a mechanism that enhances the intensity of certain frequencies because of the reflection of sound waves in a closed tube

resonance in the auditory canal enhances frequencies between about 2,000 and 5,000 Hz

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37
Q

Resonant Frequency

A

the frequency that is most strongly enhanced by resonance

the resonance frequency of a closed tube is determined by the length of the tube

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38
Q

Middle Ear

A

the small air-filled space between the auditory canal and the cochlea that contains the ossicles

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39
Q

Ossicles

A

three small bones in the middle ear that transmit vibrations from the outer to the inner ear

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40
Q

Malleus

A

the first of the ossicles of the middle ear

receives vibrations from the tympanic membrane and transmits these vibrations to the incus

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41
Q

Incus

A

the second of the ossicles of the middle ear

it transmits vibrations from the malleus to the stapes

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42
Q

Stapes

A

the last of the three ossicles of the middle ear

it receives vibrations from the incus and transmits these vibrations to the oval window of the inner ear

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43
Q

Oval Window

A

a small, membrane-covered hole in the cochlea that receives vibrations from the stapes

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44
Q

Middle Ear Muscles

A

muscles attached to the ossicles in the middle ear

the smallest skeletal muscles in the body, the contract in response to very intense sounds and dampen the vibration of the ossicles

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45
Q

Inner Ear

A

the innermost division of the ear, containing the cochlea and the receptors for hearing

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46
Q

Cochlea

A

the snail-shaped, liquid-filled structure that contains the structures of the inner ear, the most important of which are the basilar membrane, the tectorial membrane, and the hair cells

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47
Q

Cochlear Partition

A

a partition in the cochlea, extending almost its full length, that separates the scala tympani and the scala vestibuli

the organ of Corti, which contains the hair cells, is part of the cochlear partition

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48
Q

Organ of Corti

A

the major structure of the cochlear partition, containing the basilar membrane, the tectorial membrane, and the receptors for hearing

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49
Q

Hair Cells

A

neurons in the cochlea that contain small hairs, or cilia, that are displaced by vibration of the basilar membrane and fluids inside the inner ear

there are two kinds of hair cells, inner and outer

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50
Q

Basilar Membrane

A

a membrane that stretches the length of the cochlea and controls the vibration of the cochlear partition

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51
Q

Tectorial Membrane

A

a membrane that stretches the length of the cochlea and is located directly over the hair cells

vibrations of the cochlear partition cause the tectorial membrane to bend the hair cells by rubbing against them

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52
Q

Stereocilia

A

thin processes that protrude from the tops of the hair cells in the cochlea that bend in response to pressure changes

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53
Q

Tip Links

A

structures at the tops of the cilia of auditory hair cells, which stretch or slacken as the cilia move, causing ion channels to open or close

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54
Q

Phase Locking

A

firing of auditory nerves in synchrony with the phase of an auditory stimulus

55
Q

Traveling Wave

A

in the auditory system, vibration of the basilar membrane in which the peak of the vibration travels from the base of the membrane to its apex

56
Q

Apex

A

the end of the cochlea farthest from the middle ear

57
Q

Base

A

the end of the cochlea nearest the middle ear

58
Q

Tonotopic Map

A

an ordered map of frequencies created by the responding of neurons within structures in the auditory system

there is a tonotopic map of neurons along the length of the cochlea, with neurons at the apex responding best to low frequencies and neurons at the base responding best to high frequencies

59
Q

Frequency Tuning Curve

A

curve relating frequency and the threshold intensity for activating an auditory neuron

60
Q

Characteristic Frequency

A

the frequency at which a neuron in the auditory system has its lowest threshold

61
Q

Cochlear Amplifier

A

expansion and contraction of the outer hair cells in response to sound sharpens the movement of the basilar membrane to specific frequencies

this amplifying affect plays an important role in determining the frequency selectivity of auditory nerve fibers

62
Q

Place Theory

A

the proposal that the frequency of a sound is indicated by the place along the organ of Corti at which nerve firing is highest

modern place theory is based on Bekesy’s traveling wave theory of hearing

63
Q

Resolved Harmonics

A

harmonics in a complex tone that create separated peaks in basilar membrane vibration, and so can be distinguished from one another

usually lower harmonics of a complex tone

64
Q

Unresolves Harmonics

A

harmonics of a complex tone that can’t be distinguished from one another because they are not indicated by separate peaks in the basilar membrane vibration

the higher harmonics of a tone are most likely to be unresolved

65
Q

Amplitude-Modulated Noise

A

a noise sound stimulus that is amplitude modulated

66
Q

Amplitude Modulation

A

adjusting the level (or intensity) of sound stimulus so it fluctuates up and down

67
Q

Temporal Coding

A

the connection between the frequency of a sound stimulus and the timing of the auditory nerve giber firing

68
Q

Subcortical Structures

A

structure below the cerebral cortex

for example, the superior colliculus is a subcortical structure in the visual system

the cochlear nucleus and superior olivary nucleus are among the subcortical structures in the auditory system

69
Q

Cochlear Nucleus

A

the nucleus where nerve fibers from the cochlea first synapse

70
Q

Superior Olivary Nucleus

A

a nucleus along the auditory pathway from the cochlea to the auditory cortex

the superior olivary nucleus receives inputs from the cochlear nucleus

71
Q

Inferior Colliculus

A

a nucleus in the hearing system along the pathway from the cochlea to the auditory cortex

the inferior colliculus receives inputs from the superior olivary nucleus

72
Q

Medial Geniculate Nucleus

A

an auditory nucleus in the thalamus that is part of the pathway from the cochlea to the auditory cortex

the medial geniculate nucleus receives input from the inferior colliculus and transmits signals to auditory cortex

73
Q

Primary Auditory Cortex

A

an area of the temporal lobe that receives signals via nerve fibers from the medial geniculate nucleus in the thalamus

74
Q

Pitch Neurons

A

a neuron that responds to stimuli associated with a specific pitch

these neurons fire to the pitch of a complex tone even if the first harmonic or other harmonies of the tone are not present

75
Q

Presbycusis

A

a form of sensorineural hearing loss that occurs as a function of age and is usually associated with a decrease in the ability to hear high frequencies

since this loss also appears to be related to exposure to environmental sounds, it is also called sociocusis

76
Q

Noise-Induced Hearing Loss

A

a form of sensorineural hearing loss that occurs when loud noises cause degeneration of the hair cells

77
Q

Leisure Noise

A

noise associated with leisure activities such as listening to music, hunting, and woodworking

exposure to high levels of leisure noise for extended period can cause hearing loss

78
Q

Hidden Hearing Loss

A

hearing loss that occurs at high sound levels, even though the person’s thresholds, as indicated by the audiogram, are normal

79
Q

Audiogram

A

plot of hearing loss versus frequency

80
Q

What is sound?

A

pressure waves in the air produced by a vibrating object, which are detected by the auditory system

81
Q

What is the distal stimulus for sound?

A

vibrating object

82
Q

What is the proximal stimulus for sound?

A

pattern of kinetic energy at the eardrum

83
Q

What is the phase of sound?

A

point along the wave, measured in degrees

has no direct perceptual counterpart

84
Q

What is the amplitude of sound?

A

displacement of wave from peak to trough

85
Q

What is the frequency of sound?

A

number of sound wave cycles per second

86
Q

What are the physical aspects of sound?

A

phase, amplitude, frequency

87
Q

What is the loudness of sound?

A

perceptual experience of sound intensity (not “volume”)

associated with amplitude and sound pressure

to measure loudness, compare to a standard sound

to double loudness, increase dB by ~10 dB (e.g., 60 dB is twice as loud as 50 dB)

88
Q

What is the pitch of sound?

A

quality of a sound ranging from low to high; allows sounds to be ordered on a musical scale

most closely associated with frequency: ranges from 20-20000 Hz

also affected by intensity: high frequency sounds seem higher pitched as intensity increases, low frequency sounds seem lower pitched as intensity increases

duration effects: sound < 10 ms long is heard as a “click”

89
Q

What is the chromatic scale of musical notes?

A

one note is an octave above another when its frequency is double that of the comparison

octave subdivided into 12 intervals (or semitones), equally spaced logarithmically

tones in this scale match harmonic ratios found in the sound of human vocalization, specifically in English vowel sounds

other scales use different ratios to establish a scale (a.k.a. “microtonal” or “microtuned”)

90
Q

What is a fundamental?

A

lowest frequency in a Fourier spectrum of a complex sound wave

91
Q

What are harmonics?

A

components of a complex sound having frequencies that are multiples of the fundamental

the number and amplitude of harmonics contribute to the timbre of a sound

92
Q

What is timbre?

A

“character” or “nature” of a sound

makes a violin sound different from a piano

due to the different frequency components (fundamental + harmonics) produced by vibrating source stimulus

93
Q

What was the Sivian & White (1933) view of the auditory threshold?

A

each frequency has a different threshold

audibility curve: describes absolute threshold for hearing each different frequency

auditory response area: the dynamic range of intensities from threshold to pain

94
Q

What was the Fletcher & Munson (1933) view of the auditory threshold?

A

equal loudness curve: graph of decibel levels of various frequencies that seem equally loud

95
Q

How is the equal loudness curve determined?

A

present standard: 1000 Hz tone at a certain dB level

adjust intensity of other frequencies to match loudness of standard

96
Q

What factors affect the auditory threshold?

A

auditory adaptation: same sound seems softer if presented for a long time

auditory fatigue: temporary hearing loss due to high-intensity sounds, typically frequencies at and above the sound are lost

97
Q

What is the pinna?

A

the “ear” on the side of your head

channels certain sound waves

98
Q

What is the external auditory meatus (ear canal)?

A

protects middle and inner ears

amplifies frequencies 2000 to 5000 Hz via resonance: sound waves near the resonant frequency of the ear canal are reflected from the closed end of the canal, reinforcing incoming sound waves of the same frequency (like blowing across the top of a bottle)

99
Q

What is the tympanic membrane (eardrum)?

A

struck by sound waves and vibrates

transmits sound to structures in middle ear

100
Q

What are the ossicles?

A

malleus (hammer), incus (anvil), stapes (stirrup); supported by middle-ear muscles

malleus connected to eardrum; stapes to oval window

101
Q

What is the function of the ossicles?

A

concentrate vibration of eardrum (0.6 cm2) to oval window (0.032 cm2); increases pressure by ~20:1 ratio

acts as levers, increasing vibration by a factor of 1.3x

102
Q

Why is the increased pressure provided by the ossicles needed?

A

outer and middle ear filled with air; inner ear with cochlear fluid

transmitting wave into denser medium: loss of pressure

ossicles help compensate for this loss

103
Q

What is the Eustachian tube?

A

equalizes middle ear pressure with outside

104
Q

What are the semicircular canals?

A

involved in 3-D balance

vestibular sense

105
Q

What is the cochlea?

A

snail-shaped structure, filled with cochlear fluid; has 2 3/4 turns; is divided in canals

scala vestibuli (vestibular canal)
scala tympani (tympanic canal) (connected by helicotrema at apex end)
scala media (cochlear partition): formed by basilar membrane and Reissner’s membrane

106
Q

What is the Organ of Corti?

A

tectorial membrane overhangs basilar membrane, which contains 15,000 hair cells

107
Q

What are the characteristics of inner hair cells?

A

number: 3,000
cell alignment: 1 row
cilia number: 40-60/cell
cilia alignment: straight lines
function: sensory

108
Q

What are the characteristics of outer hair cells?

A

number: 12,000
cell alignment: 3-5 rows
cilia number: 100-120/cell
cilia alignment: V- or W-shaped rows
function: supportive

109
Q

What are spiral ganglion cells?

A

30,000 nerve fibres

95% are type I: 3-15 fibres/inner hair cells; large, myelinated

5% are type II: 1 fibre/10 outer hair cells; small, slow

110
Q

What is the path of transduction of sound in the ear?

A

vibration –> eardrum –> ossicles –> oval window –> vestibular canal/cochlear partition (cochlear fluid) –> basilar membrane

basilar and tectorial membranes move laterally with respect to each other

shearing force bends cilia of outer hair cells, which are embedded in tectorial membrane

cilia of inner hair cells bent by fluid flow: actin fibres link tips of cilia, when the cilia bend actin stretches and opens a “trap door”, this allows K+ ions into the hair cell which initiates the neural signal by releasing glutamate

111
Q

What are the auditory pathways?

A

axons of spiral ganglions comprise auditory nerve

superior olives send efferent fibres (feedback) to the outer hair cells

112
Q

What is tonotopic organization?

A

neurons activated by similar frequencies are found close to each other

this organization is preserved from basilar membrane to auditory cortex

40% of neurons respond to noise, clicks, bangs
60% of neurons respond to a certain frequency

113
Q

Why do 60% of neurons respond to a certain frequency?

A

complex sounds can be decomposed by Fourier analysis into component sine waves (pure tone)

this appears to be done by the auditory system

thus, we don’t need one neuron to respond to middle C on a violin, another for middle C on a piano, etc.

but some neurons are responsive to specific stimuli: squirrel monkeys have squirrel-monkey-sound-detectors

114
Q

What is place code?

A

the activity of specific neurons encodes different frequencies

115
Q

What is resonance theory?

A

basilar membrane appeared to be composed of transverse fibres

sound makes fibre vibrate like a harp-string

each fibre activated by a certain frequency

problem: basilar membrane is all connected; no independent stringlike fibres

116
Q

What is traveling wave theory?

A

traveling wave: entire membrane vibrates

basilar membranes varies in elasticity down its length: narrow/stiff at oval window (base), wide/floppy at helicotrema (apex)

each frequency has its own point of maximum displacement along the membrane: high frequencies activate hair cells at base, low frequencies activate hair cells at apex

117
Q

What is the observational evidence for traveling wave theory?

A

seeing shape of traveling wave on basilar membrane

matched predictions

118
Q

What is the evidence for traveling wave theory using the frequency tuning curve?

A

many auditory neurons display frequency tuning curve: responsive to a narrow range of frequencies

point of greatest sensitivity: characteristic frequency

partly due to selective connections from certain hair cells along the basilar membrane

119
Q

What is the evidence for traveling wave theory using tonotopic organization?

A

nerve fibres coming from base tuned to high frequencies

those from apex tuned low frequencies

120
Q

What is the evidence for traveling wave theory using stimulation deafness experiments?

A

high intensity sounds damage part of the organ of Corti

high frequencies: damage near oval window (base)
low frequencies: damage near helicotrema (apex)

121
Q

What is the evidence for traveling wave theory using motile response?

A

subsequent research showed pattern of vibration on basilar membrane is narrower than von Bekesy found

active process sharpens wave

cochlear amplifier: outer hair cells sharpen wave around the peak by tilting and changing length

two-tone suppression: present tone at characteristic frequency of a neuron, turn on another tone, close in frequency to the other, neuron’s response rate decreases, due to outer hair cells affecting movement of basilar membrane

122
Q

What is the evidence for traveling wave theory using masking experiments?

A

one sound (masker) prevents us from hearing another (target)

masking increases as masker and target frequencies become closer

masking is asymmetrical: target frequencies higher than masker are more affected than frequencies lower than masker

due to location of vibration on the basilar membrane

to reduce file size, frequencies that would have been masked anyway are removed in the encoding of digital audio files (e.g., MP3 files) a process called perceptual coding

123
Q

How is the case of the missing fundamental a problem for place coding?

A

region on basilar membrane is not moving, so how is pitch corresponding to that location heard?

present harmonics in one ear; other harmonics to other ear; missing fundamental will be perceived

this illusion must be determined by a CNS structure that integrates binaural information

Getty & Howard (1981): central pitch processor analyzes the pattern of harmonics and selects the most likely fundamental frequency that would be part of the pattern

124
Q

What is temporal code?

A

the timing of neural activity encode different frequencies

125
Q

What is frequency theory?

A

entire basilar membrane vibrates in synch with frequency

assumed that each vibration produced one action potential in all receptors

126
Q

What are the problems with frequency theory?

A

actually, only part of the membrane moves

refractory period of neurons - cells need time to recover before firing again: max frequency is 1,000/second

127
Q

What is the Volley principle?

A

groups of neurons fire alternately in volleys – some fire while others are refractory

phase locking: neuron firing is synchronized with the peak of a pure tone stimulus

frequency coded by which neurons are firing, and how much

doesn’t work well at high frequencies; phase locking works best for low frequencies (below 5000 Hz)

128
Q

Is place coding or temporal coding the correct approach?

A

there is evidence for both coding approaches; they work in combination

129
Q

What is tinnitus?

A

definition: hearing ringing in the ears, or experiencing a sound when none is present

affects 13 million North Americans, including over 2.4 million Canadians

third worst thing that can happen to you (below only intractable severe pain, and intractable severe dizziness)

can cause difficulty concentrating; anxiety and depression

most commonly caused by loud sounds, but also certain drugs, ear infections, or food allergies

early theories implicated emissions/acoustic echoes in the ear

130
Q

What are the implied central mechanisms of tinnitus?

A

patients who had cancerous auditory nerve removed developed ringing

MRIs of patients with ringing in only one ear showed area in inferior colliculus affected

some deaf people can modulate intensity and pitch of the ringing by moving their eyes left or right

131
Q

What are the current theories regarding tinnitus?

A
  1. destroying hair cells causes the brain to remap areas previously served by the destroyed hair cells, resulting in abnormal brain activity
  2. due to decreased incoming stimulation, there is less inhibition in the auditory cortex, resulting in more excitatory activity and phantom sound
132
Q

What is presbycusis?

A

age-related hearing loss, due to degeneration of hair cells and cilia

more likely to occur with increasing age

higher frequencies are more attenuated with age

presbycusis causes include: heredity, vascular diseases, ototoxic drugs, and exposure to loud noise

younger people are increasingly experiencing NIHL: 30% listen to levels of at least 91 dB for an average of 2.9 hours/day

133
Q

What are the warning signs of noise exposure/hearing loss?

A

ringing/buzzing in the ears

muffled sounds

difficulty understanding speech

difficulty following conversations over background noise

having to turn up the TV to hear it clearly

134
Q

What are the ways one can prevent noise-induced hearing loss?

A

turn down/avoid high intensity sounds

iPod and iPhone capable of up to 115 dB

most vulnerable occupations: musicians, bartenders/servers. mechanics, construction workers, dentists and assistants

wear earplugs

PSYCH 367 (15 decks)

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