Chapter 4: Sensation and Perception 4.4 (Hearing)

Question 1

Sound waves

Answer 1

changes in air pressure unfolding over time

Question 2

Pure tone

Answer 2

a simple sound wave that consists regularly of alternating regions of higher and lower air pressure, radiating outward in all directions from the source

Question 3

Frequency (or repetition rate)

Answer 3

depends on how often the peak in air pressure passes the ear or a microphone, measured in cycles per second or hertz (Hz); perceived as the pitch

Question 4

Pitch

Answer 4

how high or low a sound is, as ordered on a musical scale; low frequency (low-pitched sound) and high frequency (high-pitched sound)

Question 5

Amplitude

Answer 5

refers to the intensity of sound wave, relative to the threshold for human hearing (set at 0 decibels or dB); perceived as loudness

Question 6

Loudness

Answer 6

high amplitude (loud sound) and low amplitude (soft sound)

Question 7

Complexity

Answer 7

mixture of frequencies, influences perception of timbre; simple (pure tone) and complex (mix of frequencies)

Question 8

Timbre

Answer 8

quality of sound that allows you to distinguish two sources with the same pitch and loudness

Question 9

3 parts of the human ear

Answer 9

(1) Outer ear- collects sound waves and funnels them towards the middle ear (2) Middle ear- transmits the vibrations into the inner ear, embedded in the skull (3) Inner ear- where sound is transduced into neural impulses

Question 10

Outer ear

Answer 10

consists of the visible part of the outside of the head (pinna), the auditory canal, and the eardrum

Question 11

Eardrum

Answer 11

an airtight flap of skin that vibrates in response to sound waves gathered by the pinna and channeled into the canal

Question 12

Middle ear

Answer 12

a tiny, air-filled chamber beside the eardrum where the ossicles take airborne pressure wave at the eardrum and transfer it into fluid, act as a lever that mechanically transmits and amplifies vibrations, pushing against the oval window, to the cochlea of the inner ear

Question 13

Ossicles

Answer 13

the three smallest bones in the body named for their appearance as hammer, anvil, and stirrup

Question 14

Why do the ossicles amplify vibrations?

Answer 14

Fluid requires more energy to vibrate

Question 15

Inner ear

Answer 15

contains the cochlea, which is divided along its length by the basilar membrane

Question 16

Cochlea

Answer 16

fluid-filled tube containing cells that transduce sound vibrations into neural impulses

Question 17

Basilar membrane

Answer 17

structure in the inner ear that moves up and down in time with vibrations relayed from the ossicles, transmitted through the oval window

Question 18

Movement of sound waves in the basilar membrane

Answer 18

Sound causes basilar membrane to move up and down in a traveling wave: at low frequency, the wide, floppy tip (apex) moves the most and at high frequency, the narrow, stiff end closest to oval window (base) moves the most

Question 19

Inner hair cells

Answer 19

specialized auditory receptor neurons embedded in the basilar membrane that are stimulated when it moves up and down and the cochlear fluid moves back and forth

Question 20

Back-and-forth bending of hair cells in the cochlear fluid

Answer 20

generates rhythmic action potentials in the auditory nerve axons that travel to the brain and are timed with the pressure peaks of the original sound wave

Question 21

Which auditory nerve axons fire the most?

Answer 21

those connected to hair cells in the area of the basilar membrane that moves the most

Question 22

Neural impulses to the brain

Answer 22

action potentials in the auditory nerve travel to several regions of the brainstem, to the thalamus, then to area A1, the primary auditory cortex in the temporal lobe

Question 23

2 distinct streams of the auditory cortex

Answer 23

spatial (where) auditory features and features that allow you to identify the sound (what it is)

Question 24

Spacial auditory features

Answer 24

allows you to locate the source of a sound in space, handled by areas towards the back of the temporal lobe and in regions that may overlap with the visual dorsal stream

Question 25

Features that allow you to identify sound

Answer 25

handled by areas in the lower (ventral) part of the temporal lobe, may overlap with the ventral visual pathway

Question 26

Perceiving loudness

Answer 26

signaled by the total amount of activity in the hair cells

Question 27

Perceiving pitch

Answer 27

(1) placal code, where brain uses information about the relative acitivity of the hair cells across the whole basilar membrane (2) temporal code, where the brain uses timing of the action potentials in the auditory nerve

Question 28

Perceiving timbre

Answer 28

depends on the relative amounts of different frequency components in a sound, thus the relative activity of hair cells across basilar membrane

Question 29

Localizing a sound

Answer 29

(1) frequency of sound emphasized by the pinna depends on where it is coming from (2) speed of sound is much slower than speed of light, sounds arrive sooner at the ear nearer to the source for lower-frequency components (3) higher-frequency components are more intense in ear closer to the sound because the head blocks higher frequencies

Question 30

2 main causes of hearing loss

Answer 30

conductive hearing loss and sensorineural hearing loss

Question 31

Conductive hearing loss

Answer 31

damage in eardrum or ossicles which stop them from conducting sound waves to the cochlea, a mechanical problem, which can be corrected with medication, surgery, or sound amplification from hearing aid (conduction via surrounding bones)

Question 32

Sensorineural hearing loss

Answer 32

damage to the cochlea, hair cells, or auditory nerve that happens to almost everyone as we age

Question 33

2 main effects of Sensorineural hearing loss

Answer 33

sensitivity decreases so sounds have to be more intense (hearing aids can help) and acuity decreases so sounds smear together on the basilar membrane, making them harder to understand

Question 34

Causes of Sensorineural hearing loss

Answer 34

genetic disorders, premature birth, infections, medications, accumulated damage from sound exposure, aging

Question 35

Cochlear implant

Answer 35

an electronic device that replaces parts of the function of the hair cells, consist of a microphone and a processor, an external transmitter (on scalp) behind the ear, receiver inside skull and thin wire containing electrodes inserted into cochlea to stimulate auditory nerve

Question 36

Stereophonic hearing

Answer 36

Sound is louder when the source is closer to the ear and the sound waves arriving sooner at near ear (timing) indicates direction of the source

Question 37

Top-down processing in hearing

Answer 37

Perceptions e.g. previous exposure, background, knowledge, expectation, or context helps us make sense of what we hear