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PSYG1002 - Cognitive > Perception - Loudness and Pitch > Flashcards

Perception - Loudness and Pitch Flashcards

1
Q

What is the perceptual definition of sound?

A

Sound if the experience we have when we hear

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2
Q

What is the physical definition of sound?

A

Sound is pressure changes in air or other medium caused by the vibration of an object

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3
Q

What is a pure tone?

A

Simplest type

Occurs when changes in air pressure form perfect sinusoidal wave

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4
Q

What are the characteristics of pure tones?

A

Amplitude

Frequency

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5
Q

What is amplitude?

A

How much difference between increases and decreases in pressure

Size of variation in air pressure

Difference between peak and trough

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6
Q

What is amplitude related to?

A

Perception of loudness

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7
Q

What is frequency?

A

How many cycles of decreases and increases in pressure travel past a certain point in a second

Number of cycles per second

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8
Q

What is frequency measured in?

A

Hertz (1 Hz = 1 cycle)

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9
Q

What is frequency related to?

A

Perception of pitch

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10
Q

What are complex sounds?

A

Made up of lots of different frequencies of sound mixed together

All sound waves can be described as some combination of sine waves

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11
Q

What do natural sounds consist of?

A

Fundamental frequency superimposed by additional waveforms with higher frequencies (the harmonics)

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12
Q

What is a fundamental frequency?

A

Lowest, most dominant frequency

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13
Q

What is the ear divided into?

A

Three sub-divisions = outer, middle and inner ear

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14
Q

What are the features of the outer ear?

A

Pinnae

Auditory canal

Tympanic membrane (ear drum)

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15
Q

What is the pinnae?

A

Visible external parts of the ear

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16
Q

What is the function of the pinnae?

A

Capture sound waves and direct down ear (auditory) canals

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17
Q

What is the auditory canal?

A

~3cm tube-like structure

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18
Q

What is the function of the auditory canal?

A

Protects middle ear

19
Q

What is the tympanic membrane (ear drum)?

A

Cone-shaped membrane separating outer and middle ear

20
Q

What is the function of the tympanic membrane (ear drum)?

A

Sound waves induce difference in pressure either side of tympanic membrane, causing it to vibrate

Larger amplitude sounds result in larger vibrations

Higher frequency sounds result in faster vibrations

21
Q

What are the features of the middle ear?

A

Small cavity (~2 cubic cm) containing ossicles (smallest bones in the human body)

22
Q

What are the ossicles?

A

Malleus (hammer)

Incus (anvil)

Stapes (stirrup)

23
Q

What is the function of the ossicles?

A

Bones amplify vibrations of tympanic membrane and transmit to inner ear at oval window

24
Q

What are the features of the inner ear?

A

Main structure is cochlea (snail-like liquid-filled organ)

Basilar membrane

25
Q

What are the features of the cochlea?

A

Three parallel canals - vestibular, middle, tympanic

26
Q

What is the basilar membrane?

A

Separates middle and tympanic canals

27
Q

What is the function of the inner ear?

A

Vibration of oval window displaces fluid in cochlea, resulting in change of pressure which moves up and down spiral structure

Auditory transduction triggered by motion of basilar membrane

Pressure waves in cochlea causing basilar membrane to move

28
Q

What is auditory transduction?

A

Motion of basilar membrane translated into neural signals by structures in Organ of Corti, which extends along its surface

Voltage generated when specialised hair cells contained within Organ of Corti bent

Produces impulses in auditory nerve cells which are sent to brain

Hair cells extremely sensitive - overstimulation by loud sounds can damage hair cells and lead to hearing loss

29
Q

How are sound levels measured to describe differences in amplitude?

A

In decibels

Logarithmic scale

Change of 20dB corresponds to ten-fold increase in amplitude

30
Q

What is rate code?

A

Sound amplitude coded in the firing range of auditory nerve fibres

Responses increase with increasing sound intensity

31
Q

How does a high amplitude affect the rate code?

A

High amplitude

High firing rate

High rate code

32
Q

How does the rate code allow us to discriminate loudness across a range of sound levels?

A

Some fibres have high spontaneous rates and saturate rapidly while others have low spontaneous rates and saturate slowly

33
Q

Are amplitude and loudness directly proportional?

A

No

For sound to be perceived as twice as loud, amplitude needs to be increased by factor of ~3.16 (10dB)

34
Q

Does loudness depend on frequency?

A

Yes

Auditory systems not equally sensitive to all sound frequency

35
Q

If the frequency is higher, is the pitch higher or lower?

A

Higher

36
Q

What is the lowest and highest frequencies that a human can hear?

A

Lowest = 20Hz (below can feel the sound)

Highest = 20,000Hz (20kHz)

37
Q

What are the two ways to code frequency?

A

Place code

Timing code

38
Q

What is the place code?

A

Different auditory nerve fibres respond to different frequencies

Sound frequencies causes vibration in specific areas along the basilar membrane

39
Q

Where do low frequencies cause vibrations in the basilar membrane?

A

Near apex

40
Q

Where do high frequencies cause vibrations in the basilar membrane?

A

Near base

41
Q

What is the timing code?

A

Not only which auditory nerve fibres respond but when they respond

Hair cells respond in little packets of firing, not all the time

Auditory nerve responses synchronised to changes in pressure - property called phase-locking

Occurs up to frequencies of about 400Hz (lower frequencies)

42
Q

What has been suggested by experiments using electrical stimulation via cochlea implants?

A

Both place and timing of stimulation affect perception of pitch

43
Q

Why does the same note sound different on different instruments?

A

Pitch determined primarily by fundamental frequency of sound

Instruments have same fundamental frequencies but different harmonics

Number, frequency ratios and relative amplitudes of the harmonics dictate the quality or timbre of sound

44
Q

What is the missing fundamental illusion?

A

Continue to perceive pitch consistent with missing fundamental frequency

Pitch isn’t simply determined by cochlea, brain infers missing fundamental from harmonics

PSYG1002 - Cognitive (7 decks)

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