Psy3051 - Perception - Chpt 11 & 12 - Auditory Sytem

Front 1

What are the two definitions of sound?

Back 1

1. Physical - sound is pressure changes in the air or other medium
2. Perceptual - sound is the experience we have when we hear

Front 2

What is rarefaction?

Back 2

the decreased density of air molecules caused by pressure changes

Front 3

What is condensation?

Back 3

the increased density of air molecules caused by pressure changes

Front 4

How does a speaker produce a sound wave?

Back 4

- movement in the diaphragm outwards
- causes condensation
- movement back causes rarefaction
- cycling of this motion causes alternating high and low pressure regions that travel through the air

Front 5

What is a pure tone?

Back 5

simple kind of sound wave that occurs when pressure changes in the air occur in pattern described by a sine wave

Front 6

What is a sine wave?

Back 6

a mathematical function

Front 7

What are two simple sound wave descriptors?

Back 7

Frequency and amplitude

Front 8

What is frequency?

Back 8

the number of times per second the pressure changes repeat

Front 9

What is amplitude?

Back 9

the size of the pressure change

Front 10

What does a decibel measure?

Back 10

the amplitude or physical size of the wavelength used to measure the perception of loudness

Front 11

How is frequency measured?

Back 11

using hertz (Hz) which is cycles per second

Front 12

What is the perception of frequency?

Back 12

pitch

Front 13

What is pitch?

Back 13

the perception of high to low sounds

Front 14

What is tone height?

Back 14

An increase in frequency or pitch

Front 15

What is a tone that consists of a number of pure tones?

Back 15

a complex tone

Front 16

What is the repetition rate of a complex tone?

Back 16

the fundamental frequency

Front 17

What is the name of the technique in which a number of sine-wave components are added together to create a complex tone?

Back 17

additive synthesis

Front 18

What does the single pure tone used at the start of the additive synthesis determine?

Back 18

the fundamental frequency

Front 19

What are the name of additional tones added to the fundamental frequency?

Back 19

harmonics

Front 20

Periodic complex tones consist of a number of pure tones called what?

Back 20

harmonics

Front 21

What is the display of harmonics of a complex sound called?

Back 21

frequency spectrum

Front 22

What is an attack of tones?

Back 22

build up of sound at the beginning of a tone

Front 23

What is the decay of tones?

Back 23

decrease in sound at the end of a tone

Front 24

The perceived pitch of complex sounds is determined by what?

Back 24

fundamental frequency

Front 25

The constancy of pitch even when the fundamental is removed is known as what?

Back 25

effect of the missing fundamental - the pitch won;t change but ht equality of Timbre will

Front 26

We hear sound only in a specific range of frequencies called the what?

Back 26

range of hearing

Front 27

What is the audibility curve?

Back 27

the threshold for hearing

Front 28

Loudness is determined by a combination of what?

Back 28

amplitude and frequency

Front 29

What is timbre?

Back 29

all other perceptual aspects of sound besides loudness, pitch and duration

Front 30

What does timbre reflect?

Back 30

the number and magnitude of harmonics

Front 31

What does the removal of the first harmonic results is a sound with the same pitch but a different timbre, this sound is known as?

Back 31

a periodicity pitch

Front 32

What is the human range of hearing?

Back 32

20 to 20,000 Hz

Front 33

Humans are most sensitive to what range of sound?

Back 33

2,000 to 4,000 Hz

Front 34

What is the auditory response areas?

Back 34

the area that falles between the auditory curve and the threshold for feeling

Front 35

What is the threshold for feeling?

Back 35

the level which sounds above this can cause humans pain and damage

Front 36

What is the Pinnae?

Back 36

the ear structure on the outside of the head

Front 37

What forms the outer ear?

Back 37

the pinnae and the auditory canal

Front 38

What does the auditory canal protect?

Back 38

the delicate structures of the middle ear

Front 39

What is another name for the eardrum?

Back 39

the tympanic membrane

Front 40

When does resonance occur in the auditory canal?

Back 40

when sound waves are reflected back from the closed end of the auditory canal interact with sound waves that are entering the canal

Front 41

In addition to the protective function what is the other function of the auditory canal?

Back 41

the enhance the intensities of sounds by means of the physical principle of resonance

Front 42

Resonance reinforces some of the sounds frequencies, with the frequency that is reinforced the most being determined by the length of the canal. What do we call this frequency?

Back 42

The resonant frequency

Front 43

What do sounds do to the tympanic membrane at the end of the auditory canal?

Back 43

they cause it to vibrate

Front 44

What is the purpose of a vibrating tympanic membrane?

Back 44

To send vibration to the middle ear structures

Front 45

What are the three middle ear structures or ossicles?

Back 45

1. malleus
2. incus
3. stapes

Front 46

What is the purpose of the ossicles?

Back 46

to intensify the vibrations so that they can be transmitted through the liquid filled inner ear by concentrating the vibration onto the stapes which increases the pressure factor by 20 and through the lever action of the ossicles effecting this power onto the membrane to thee inner ear

Front 47

What are the purpose of the middle ear muscles and what is unique about theses muscles?

Back 47

they are attached ot he ossicle and at very high sound intensities they contract to dampen the ossicles vibrations and protect the ear from pain and damage.
They are the smallest skeletal muscles in the body.

Front 48

What is the main sructure ei the middle ear?

Back 48

cochlea

Front 49

How is the liquid filled cochlea sent into vibration?

Back 49

by movement of the stapes against the oval window

Front 50

What are the three broad structures of the cochlear?

Back 50

1. scala vestibuli - upper half
2. scala tympani - lower half
3. cochlea partition - runs the entire length from the base to the apex

Front 51

How big in the cochlea?

Back 51

2mm in diameter and 35mm in length

Front 52

What does the cochlea partition contain?

Back 52

organ or corti

Front 53

What are the main 4 structures in the organ or corti?

Back 53

1. inner and outer hair cells
2. basilar membrane
3. tectorial membrane

Front 54

What is purpose of the hair cells in the organ or corti and what are they also known as?

Back 54

the hair cells are the receptors for hearing and are known as cilia

Front 55

How many inner and outer hair cells are there in the inner ear?

Back 55

3,500 inner and 12,000 outer

Front 56

What does the basilar membrane do?

Back 56

it supports the organ of corti and vibrates in response to sound

Front 57

What does the tectorial membrane do?

Back 57

extends over the hair cells and its presence causes movement of the cilia

Front 58

Which hair cells are responsible for transduction?

Back 58

inner hair cells

Front 59

What is the major function of the out hair cells?

Back 59

to increase the vibration of the basilar membrane

Front 60

Pressure changes in the liquid inside the cochlea cause what to movement up and down?

Back 60

the cohlea partition

Front 61

What are two effects that happen as a result of the cochlea partition moving up and down?

Back 61

1. it sets the organ of corti into a up and down vibration
2. it causes the tectorial membrane to move back and forth

Front 62

What do the inner and outer hair cells do when the tectorial membrane moves back and forth?

Back 62

the inner hair cells bend in response to the movement in liquid and the outer hair cells bend in response to the the tectorial membrane's back and forth motion

Front 63

When the cilia bend movement back and forth causes what to happen in the cells?

Back 63

the ion channels to open or close depending on the direction of the motion

Front 64

The amount the cilia of the inner hair must bend to cause and electrical signal is what?

Back 64

very small

Front 65

What are the two ways nerve fibers signal frequency?

Back 65

1. which fibers are firing - specific groups of hair on the basilar membrane activate a specific group of nerve fibers
2. How they fire - the rate or pattern of firing of the nerve impulse

Front 66

Beksy's place theory of hearing state?

Back 66

That the frequency of sound is indicated by the place along the cochlea at which nerve firing is highest.

Front 67

What are two important facts about the structure of the basilar membrane?

Back 67

The base of the membrane is:
1. three to four times narrower than the apex, and
2. 100 times stiffer

Front 68

Which end of the basilar membrane is wider?

Back 68

the apex

Front 69

How did Beksy determine that the basilar membrane vibrated in response to different frequencies?

Back 69

1. observing the vibration of the membrane in cadavers
2. he built a model of the cochlea which took int account the physical properties of the basilar membrane

Front 70

The envelope of the travelling wave down the basilar membrane causes maximum displacement at a point. What occurs at this point?

Back 70

strongest neural firing the this pont where the hair cells are stimulated most strongly as a result of the displacement.

Front 71

What are the two conclusions Beksy made from his observations of the envelope of travelling wave on the basilar membrane?

Back 71

1. At the envelopes peak amplitude there will be the strongest neural firing
2. The position of the peak amplitude is a function of the frequency of sound

Front 72

Where on the basilar membrane do low and high frequencies cause maximum neural firing?

Back 72

low frequencies cause maximum firing towards the apex and high frequencies towards the base

Front 73

While Beksy's research showed no difference in response for close frequencies later research showed what?

Back 73

That in live people the outer hair cells show a motile response by slightly tilting and changing in length and therefore amplifying and sharpening the vibrations

Front 74

What is the motile response?

Back 74

The movement of the outer hair cells up and down which amplifies and sharpens the vibration of the basilar membrane

Front 75

What is it called when neurons fire at the same pace in the sound stimulus?

Back 75

phase locking

Front 76

The connection between the frequency of a sound stimulus and the timing of the auditory nerve fiber firing is called what?

Back 76

temporal coding

Front 77

What happens when the firing of a number of auditory nerves fibers is phase locked to the stimulus?

Back 77

they fire in bursts separated by silent intervals and the timing of these bursts matches the frequency of the sound stimulus.

Front 78

Up to what maximum frequency does phase locking occur?

Back 78

4,000Hz

Front 79

Frequency is coded in the cochlea and auditory nerve based on both which fibers are firing (place coding) and also what?

Back 79

and on the timing of the nerve impulse in the auditory nerve fibers (temporal coding).

Front 80

While place coding occurs across the entire range of hearing temporal coding occurs up to what?

Back 80

4,000 Hz at which point phase locking stops operating

Front 81

The auditory nerves synapses in what sequence through which cortical structures ?

Back 81

1. cochlea nucleus to the
2. superior olivary in the brain stem to the
3. inferior colliculus in the mid brain to the
4. medial geniculate nucleus in the thalamus to the
5. Primary receiving areas A1 in the temporal lobe

Front 82

What is processing in the superior olivary nuclei important for?

Back 82

determining auditory localisation

Front 83

What is meant by hierarchical processing occurs in the cortex?

Back 83

That simple sounds are processing in the core area which includes the primary receiving area but more complex sounds cause activation in the belt and parabelt areas.

Front 84

The what or ventral stream of hearing starts from the anterior part of the core and belt and extends to where?

Back 84

the prefrontal cortex

Front 85

The where or dorsal stream of hearing starts from the posterior part of the core and belt and extends to where?

Back 85

parietal cortex and the prefrontal cortex

Front 86

What are the what and where streams in hearing responsible for?

Back 86

the what or ventral stream is responsible for identifying sounds and the where or dorsal stream is responsible for locating sounds

Front 87

Where are the tonotropic maps found?

Back 87

in the primary receiving area (A1)

Front 88

Where are neurons that respond to high and low frequencies on the the tonotropic map?

Back 88

neurons that repsond to high frequency are on the right and low frequencies on the left

Front 89

What surrounds and observer and exists wherever there is sound?

Back 89

the auditory space

Front 90

What are the three dimensions in localising sound?

Back 90

1. Azimuth coordinates - position left to right
2. Elevation coordinates - position up and down
3. Distance coordinates - position from observer

Front 91

Location cues must be what?

Back 91

calculated

Front 92

Where can people hear sounds the best?

Back 92

when they occur directly in front of them

Front 93

What are the two binaural cues for sound localisation?

Back 93

1. ITD - Interaural time difference

2. ILD - Interaural Level Difference

Front 94

What are binaural cues?

Back 94

cues based on the comparison of the signals received by the left and right ear

Front 95

Where does the processing of interaural sound cues occur?

Back 95

superior olivary complex (SOC)

Front 96

What is the first site of binaural action processing?

Back 96

the SOC - superior olivary complex

Front 97

What is the ITD based on?

Back 97

the difference in time when the sound reaches the left and right ears

Front 98

When is the ITD ineffective?

Back 98

for low frequency sounds

Front 99

What is the ILD?

Back 99

difference in sound pressure level reaching the two ears

Front 100

When is the ILD ineffective?

Back 100

for high frequencies as the head casts and acoustic shadow

Front 101

What is the cone of confusion?

Back 101

an area to each side of the ear where the ILD and ITD are unable to accurately provide accurate location information

Front 102

What is the primary monaural cue for localisation?

Back 102

the spectra cue or pinna cue

Front 103

Why is the pinna cue a spectra cue?

Back 103

because it can process all frequencies across the spectrum

Front 104

The pinna affects what?

Back 104

the intensity of the frequencies

Front 105

How does the pinna assist in localising a sound?

Back 105

the way sounds bounce off the pinna cause differences in the frequency spectra for sounds coming from different locations

Front 106

Reflections of high frequencies from the convolutions of the pinna produce elevation and front-back what?

Back 106

dependant spectral transformations int he sound

Front 107

Pinna spectral transformations are only cues for what type of sound localisation?

Back 107

vertical or elevation

Front 108

What are the two types of neurons proposed to respond to ITD?

Back 108

1. narrowly tuned ITD neurons
2. broadly tuned ITD neurons

Front 109

Where are narrowly tuned ITC neurons found?

Back 109

int he inferior colliculus and the superior olivary nuclei

Front 110

Narrowly tuned neurons are a from of what type of coding?

Back 110

specificity

Front 111

What is the main difference between narrowly tuned ITD neurons and broadly tuned ITD neurons?

Back 111

narrowly tuned neurons respond best to specific ITD, broadly tuned neurons in each hemisphere respond best when sound is received from the contralateral ear

Front 112

What are three facets of Jeffress model of narrowly tuned ITD neurons?

Back 112

1. these neurons receive signals from both ears
2. coincidence detectors fire when ITD = 0
3. other neurons in the circuit fire depending on the calculated ITD

Front 113

What does research on gerbals indicate about broadly tuned neurons?

Back 113

1. that neurons in each hemisphere fire best when sound is received form the contralateral ear
2. the location of sound is indicated by the ratio of responding of two types of neurons
3. this is a distributed coding system

Front 114

What is the process by which all sound sources in the auditory scene are separated into belonging to to individual perceptions/streams?

Back 114

auditory scene analysis

Front 115

What is the main tool used for auditory scene analysis?

Back 115

Auditory grouping

Front 116

What is auditory grouping?

Back 116

heuristics that help us perceptually organise elements of an auditory scene

Front 117

What are the 5 types of auditory grouping?

Back 117

1. Location
2. Similarity of timbre and pitch
3. Proximity in time
4. Auditory continuity
5. Experience

Front 118

Explain the location heuristic.

Back 118

that a single source of sound tends to come from one location and to move continuously

Front 119

Explain the timbre and pitch heuristic.

Back 119

sounds that have the same timbre and pitch are often produced by the same source

Front 120

What is auditory stream segregation?

Back 120

the ability to perceive a difference in melody coming from one source when high and low notes are played rapidly but not when they played slowly

Front 121

Explain the auditory stream segregation experiment by Bregman and Campbell.

Back 121

- stimuli were alternating high and low notes
- when stimuli played slowly the perception is hearing high and low tones played alternately
- when the stimuli is played rapidly the listener hears two different streams, one high and one low

Front 122

explain the auditory stream segregation experiment by Bregman and Rudnicky.

Back 122

- listener hears two standard tones (X&Y) and can easily perceive the order
- then two distractor tones (D) are place between X&Y and the listener can no longer perceive the order of X&Y
- adding a series of captor tones (C) forms an auditory stream with the D tones and the listener can hear the order of X&Y

Front 123

What is the Proximity in Time heuristic?

Back 123

sounds that occur in rapid succession usually come formt eh same source

Front 124

What is the auditory continuity heuristic?

Back 124

sounds that stay constant or change smoothly usually come form the same source

Front 125

What does onset time indicate about sources of sounds?

Back 125

sounds that start at different times are likely to come for different sources

Front 126

Explain the good continuation experiment by warren et al.

Back 126

- tones were presented interrupted by gaps of silence
- in the silence condition listeners perceived the gaps in sound
- in the noise condition listeners perceived a continuation of the tone

Front 127

What is a melody schema?

Back 127

a representation of a familar melody that is stored in a persons memory

Front 128

Explain the experience heuristic of auditory scene analysis.

Back 128

memory of particular sounds can impact the detection and recognition of the sounds or melodies amongst other noise

Front 129

What is direct sound?

Back 129

sound that reaches the listeners ears straight form the source

Front 130

What is indirect sound?

Back 130

sound that is reflected off of environmental surfaces and then to the listener

Front 131

Where is there more likely to be indirect sound?

Back 131

inside a room

Front 132

Explain the leader lag experiment by Litovsky et al.

Back 132

- listeners sat between two speakers: a lead speaker and a lag speaker
- when sound comes form the lead speaker followed by the lag speaker with a long delay listeners hear two sounds
- when the delay is decreased to between 5 to 20 ms the listener hears the sound as only coming from the lead speaker - the precedence effect

Front 133

What is the precedence effect?

Back 133

you perceive the sound as coming only from nearest speaker as it has reached your ears first.

Front 134

What are the factors that effect perception in concert halls?

Back 134

1. Reverberation time
2. Intimacy time
3. Bass ratio
4. Spaciousness factor

Front 135

What is reverberation time?

Back 135

the time it takes for a sound to reach 1/1000th of its original pressure. Ideal reverberation time is 2 seconds, if its too long it sounds muddled and if it;s too short it sounds dead

Front 136

What is intimacy time?

Back 136

the time between when a sound leaves its source and when the first reflection arrives. ideal time is around 20ms

Front 137

What is Bass ratio?

Back 137

ratio of low to middle frequencies reflected form surfaces. High bass ratios are best.

Front 138

What is spaciousness factor?

Back 138

fraction of all the sound received by the listener that is indirect. High spaciousness factor are best.

Front 139

What do concert halls need to consider the density of the chair cushions?

Back 139

because they absorb sound and therefore reduce reflections resulting in decreased sound quality

Front 140

What is the ideal reverberation for classrooms?

Back 140

- .4 to .6 for small classrooms
- 1.0 to 1.5 for auditoriums
- most classrooms have a time of 1 second or more

Front 141

What is problematic in classrooms?

Back 141

background noise

Front 142

What is the best signal to noise ratio in a class room to maximise the ability for the speaker to be heard?

Back 142

signal to noise ratios should be +10 to +15 db or more