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C82COG - Perception > Hearing and the auditory system > Flashcards

Hearing and the auditory system Flashcards

1
Q

What is sound?

A

Loudness and pitch conveyed by vibrations in the air to the ear and then to the auditory system.

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2
Q

What are the main parts of the auditory system?

A

The ear, the cochlea, the 8th cranial nerve, brainstem and midbrain, auditory cortex.

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3
Q

How does sound travel through the air?

A

In waves - the compression and expansion of air molecules (increase and decrease of pressure) produced by vibration.

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4
Q

What does the amplitude of the sine wave represent?

A

The amount of vibration.

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5
Q

What does the wavelength of the sine wave represent?

A

The frequency of vibration.

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6
Q

What does a Reubens’ tube show?

A

A standing wave of sound in fire! High pressure doesn’t allow gas to come out, low pressure allows more gas.

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7
Q

What is sound pressure, or P?

A

The root mean square of the deviation in pressure around the baseline atmospheric pressure (uPa).

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8
Q

What is sound intensity, or I?

A

The acoustical energy per unit time and unit area (W/m^2).

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9
Q

What does this mean: I=kP^2

A

Sound intensity is proportional to the square of the sound pressure.

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10
Q

What is the smallest detectable sound pressure/intensity?

A

20uPa or 10^-12 W/m^2.

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11
Q

What is the threshold for pain, and what factor is this of the smallest detectable sound?

A

10 W/m^2, 1 trillion.

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12
Q

What is the logarithmic scale used to represent sound pressure/intensity?

A

Decibel sound pressure level - dB SPL.

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13
Q

What is the threshold of hearing in decibels?

A

0dB.

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14
Q

How loud, in decibels, are leaves rustling?

A

About 20.

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15
Q

How loud, in decibels, is a library?

A

About 40.

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16
Q

How loud, in decibels, is an office or classroom?

A

About 70.

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17
Q

How loud, in decibels, is a heavy truck?

A

About 90.

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18
Q

How loud, in decibels, is a jackhammer?

A

105.

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19
Q

How loud, in decibels, is a plane taking off?

A

Over 130.

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20
Q

What is the pain threshold in decibels?

A

About 100dB.

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21
Q

What is the 10dB rule?

A

For every increase of 10dB, the sound level doubles.

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22
Q

What does uPa stand for?

A

Micro pascals.

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23
Q

What does Weber’s Law state?

A

The JND, deltaI, is proportional to the intensity I of the stimulus: deltaI/I = k

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24
Q

For sound intensity, what is the approximate value of k in Weber’s Law?

A

0.2

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25
Q

What does Weber’s Law imply for sound intensity?

A

We are sensitive to about a 20% change in intensity, approximately 1dB.

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26
Q

Why don’t we hear loud noises due to pressure changes when we walk?

A

The frequency when we walk is too low to hear. 2-3Hz.

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27
Q

How does the audibility threshold change with frequency?

A

As frequency increases, the threshold decreases, with a small peak around 800Hz.

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28
Q

What is the lowest frequency we can hear?

A

20Hz.

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29
Q

Can we detect sounds below 20Hz?

A

Yes, we feel them.

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30
Q

What is the highest frequency we can hear?

A

2000Hz.

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31
Q

What scale is used for frequency?

A 
Level scale - log10
Frequency scale (octave) - log2.
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32
Q

What does the frequency range correspond to?

A

10 octaves.

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33
Q

Weber’s law applies to frequency discrimination. What does this mean?

A

JND deltaf is proportional to f.

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34
Q

According to Weber’s Law, what frequencies can we discriminate between?

A
  • between 1000 and 1001 Hz
  • Weber fraction (k) of 0.001
  • a 0.1% change - a semitone is 6%.
35
Q

How is pitch defined mathematically?

A

Asin(2pift+&)

Where A is sound pressure, f is frequency, and & is phase.

36
Q

What drives our perception of pitch?

A

Frequency.

37
Q

What are the three parts of the ear?

A

Outer, middle, inner.

38
Q

What are the parts of the outer ear?

A

Concha, ear canal, pinna, and tympanic membrane (ear drum).

39
Q

What are the parts of the middle ear?

A

Malleus, incus, tensor tympani muscle, stapes, tympanic membrane, stapedius muscle, round window, base of stapes in oval window,

40
Q

What are the parts of the inner ear?

A

Semi-circular canals, oval window, vestibular nerve, auditory nerve (cochlear nerve?), cochlea, ?round window.

41
Q

What can be seen in a cross section of the cochlea?

A

Tectorial membrane, vestibular canal, Reissner’s membrane, middle canal, inner hair cells, spiral ganglion, tympanic canal, basilar membrane, outer hair cells.

42
Q

What do outer hair cells do?

A

They move with pressure changes, causing the release of ions, leading to the release of NTs and auditory nerve APs.

43
Q

What is in the corti, the small centre section of the cochlea?

A

Tectorial membrane, stereocilia, afferent fibres, basilar membrane, inner and outer hair cells, tunnel of corti, and efferent fibres.

44
Q

How does sound cause the movement of inner and outer hair cells?

A

Sound induces vibration of the tectorial membrane, which moves back and forth over the top of the hairs, alternating around 1000 times per second.

45
Q

What is meant by frequency decomposition?

A

How we detect different frequency waves through the cochlea - different parts of it respond to different frequencies.

46
Q

What type of frequency does the cochlea near the stapes (base) respond to?

A

High frequencies.

47
Q

What part of the cochlea responds to low frequency sounds?

A

The apex.

48
Q

What does Fourier analysis mean when applied to sound waves?

A

Through the combination of different waves, any sound can be made.

49
Q

How does the brain amplify sounds of a certain frequency?

A

It causes the outer hair cells to amplify certain frequencies by pressing on the basilar membrane.

50
Q

What is the difference between high and low spontaneous rate fibres?

A

High fibres respond more at low sound intensities and reach their maximum firing rate earlier than low fibres, which respond more to high sound intensities.

51
Q

What is phase locking?

A

How firing rate responds to frequency - there is a delay between the highest pressure and the highest firing rate due to having to transmit through membrane, hairs, release ions and NTs, then causing APs.

52
Q

What is frequency tuning?

A

The lowest intensity needed to cause an action potential in a particular neuron - low frequency at apex, high at stapes.

53
Q

What is the idea of critical bands and auditory masking?

A

When pts are asked to detect a tone whilst hearing a masking noise, the more similar the frequencies are (whether they fall within a critical band) determines the signal threshold.

54
Q

What brain structures are involved in the auditory system?

A

Auditory nerve, rostral medulla (dorsal, posteroventral and anteroventral cochlear nuclei), mid pons (superior olive), pons-midbrain junction (nucleus of lateral leminiscus), caudal midbrain (inferior colliculus), rostral midbrain (medial geniculate complex of the thalamus), and the cerebrum (primary auditory cortex).

55
Q

Where does binaural processing occur?

A

In the mid pons - the superior olive. Input from both cochleas are combined.

56
Q

What do LSO and MSO stand for?

A

Lateral and medial superior olive.

57
Q

What are the two binaural cues?

A

Interaural time difference and interaural level difference.

58
Q

What do binaural cues determine?

A

The location of the sound.

59
Q

What does interaural time difference arise from?

A

The difference in distance and therefore time a sound needs to travel to reach each ear.

60
Q

What is the maximum ITD in humans?

A

600 micro seconds.

61
Q

What frequencies is ITD useful for, and why?

A

Below 1000Hz, because it requires phase locking.

62
Q

Why does interaural level difference arise?

A

Because the head casts an acoustic shadow.

63
Q

What is the maximum ILD in humans?

A

20dB.

64
Q

What frequencies is ILD useful for?

A

Frequencies above 1000Hz.

65
Q

What is an example of acoustic shadowing in everyday life?

A

Hearing the bass of music from a passing car, but not the higher frequencies as they’re shadowed by walls etc.

66
Q

What frequency sounds do we have limited information on the location of and why?

A

1000Hz because of the boundaries of ITD and ILD.

67
Q

What is reverberation?

A

How sounds reflect/echo off surfaces in rooms.

68
Q

What is the precedence effect?

A

The fact that although sound reflections arrive at different times, the auditory system gives precedence to early arriving sounds, so we only hear the sound from one direction.

69
Q

How do arctic foxes determine sound location without using their visual system?

A

They move their heads to better determine the location.

70
Q

How well do barn owls determine sound location?

A

Very well, due to weirdly placed ears (by their eyes) aided by feathers, meaning that they encode ITD and ILD very well.

71
Q

Where is speech processed?

A

The primary auditory cortex.

72
Q

Name the main parts of the vocal tract used in producing phonemes.

A

Palate, tongue, epiglottis, vocal cords, larynx, trachea, oesophagus, and lungs.

73
Q

Name the main parts of the vocal tract used in shaping sounds.

A

Nasal tract, hard palate, teeth, lower lip, jaw, tongue, epiglottis, pharynx, soft palate, oral tract, and alveolar ridge.

74
Q

What three parts of the vocal tract are used for constrictions?

A

Teeth, lower lip, and tongue.

75
Q

What does vowel output look like in terms of a graph of frequency by amplitude?

A

There are three formers - humps formed of amplification and attenuation.

76
Q

How can the three vowel formers be moved (changing peak alignment), and what does this do?

A

By tongue position, forming different vowels.

77
Q

What are the unvoiced plosive consonants?

A

P, t, and k.

78
Q

What are the voiced plosive consonants?

A

B, d, and g.

79
Q

What are the labial plosive consonants?

A

P and b.

80
Q

What are the dental/alveolar plosive consonants?

A

T and d.

81
Q

What are the velar (hard palate) plosive consonants?

A

K and g.

82
Q

What are the nasal plosive consonants?

A

M and n.

83
Q

What is the McGurk effect?

A

When a video of someone saying ‘gah’ with an audio track of ‘bah’ is presented to a participant, they interpret it as ‘dah’.

84
Q

What are the applications of findings about hearing?

A

9 million hearing impaired individuals benefit from hearing aids.
Also affects room design and mp3 file compression (keeps sound with 90% size reduction).

C82COG - Perception (9 decks)

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