Lecture - auditory

Question 1

sound

Answer 1

A vibrating object creates alternating waves of condensation and rarefaction in a medium

Question 2

The pattern of condensation and rarefaction is

Answer 2

propagated away from the vibrating source like ripples in water

Question 3

sound intensity progressively decreases with

Answer 3

distance from the source

Question 4

velocity of sound in air

Answer 4

750 mph (1250 km/h, sound barrier)

Question 5

velocity is greater in

Answer 5

denser media (wood, metal, water).

Question 6

pure tone

Answer 6

single sinusoidal waveform. pressure is plotted as a sine wave. frequency is the number of cycles per second, or Hertz. amplitude is the magnitude of the pressure wave measured in decibels (dB).

Question 7

perceiving pure tones

Answer 7

pure tones don’t exist in the natural world. the frequency of the sound will determine the pitch you perceive. The amplitude of the sound determines its loudness.

Question 8

Audible frequency spectrum:

Answer 8

20 - 20,000 Hz

Question 9

complexity

Answer 9

determines the timbre.

Question 10

natural sounds are

Answer 10

complex patterns of vibrations.

Question 11

fourier analysis

Answer 11

breaks natural sounds down into sine waves.

Question 12

complex relationship between natural sounds and

Answer 12

perceived frequency.

Question 13

the decibel scale

Answer 13

dB = 20(logP1/P0)
Because the dynamic range of the ear is so great, sound amplitude is expressed on a ratio scale (log 10), not an interval (linear) scale.

Question 14

0 dB

Answer 14

corresponds to the average human’s absolute threshold for hearing.

Question 15

6 dB increase

Answer 15

corresponds (approximately) to a doubling of sound pressure

Question 16

1 Pa (unit of pressure, “Pascal”) =

Answer 16

1N/m2 (1 Newton/meter2)

Question 17

Sound waves enter the

Answer 17

auditory canal of the ear and then cause the tympanic membrane (the eardrum) to vibrate. This sets in motion the bones of the middle ear, the ossicles, which trigger vibrations of the oval window: hammer (malleus), anvil (incus), and stirrup (stapes).

Question 18

the ear pathway

Answer 18

Sound wave > eardrum > ossicles (hammer, anvil, stirrup) > oval window

Question 19

Vibration of the oval window sets in motion the

Answer 19

fluid of the cochlea, which is possible due to the movement of the round window.

Question 20

The cochlea’s organ of Corti

Answer 20

is the auditory receptor organ

Question 21

outer and middle ear are

Answer 21

filled with air

Question 22

inner ear is

Answer 22

filled with fluid which is not compressible as air is. The ossicles amplify the vibration and the round window allows movement of the fluid in the cochlea.

Question 23

the oval and round windows have membranes so

Answer 23

they move, but liquid does not enter nor escape (from and to the middle ear).

Question 24

The basilar membrane vibrates in response to

Answer 24

to sound hitting the eardrum and the frequency of the sound is encoded by the place on the basilar membrane that is
maximally vibrated by the sound.

Question 25

The basilar membrane is narrower and stiffer at the

Answer 25

basal end.

Question 26

The basilar membrane is wider and less tightly stretched at the

Answer 26

apical end

Question 27

Different frequencies produce

Answer 27

maximal stimulation of hair cells at different points along the basilar membrane

Question 28

the basilar membrane and the auditory pathway organization is

Answer 28

Tonotopic (frequency)

Question 29

Vibrations travel from the

Answer 29

base to the apex of the basilar membrane. High frequencies peak near the base, but lower frequencies continue on and peak at the apex.

Question 30

organ of corti is composed of two membranes

Answer 30

basilar membrane and tectorial membrane

Question 31

basilar membrane

Answer 31

auditory receptors (hair cells) are mounted here

Question 32

Tectorial membrane

Answer 32

rests on top of the hair cells

Question 33

Transduction is produced by

Answer 33

the movement of hairs. Stimulation of hair cells triggers action potentials in the auditory nerve.

Question 34

Basilar membrane vibration causes deflection of hair bundles

Answer 34

The motion of the traveling wave creates shearing forces on the hair cell (stereocilia)

Question 35

hair cells

Answer 35

in humans there are about 3,750 inner hair cells per ear

Question 36

tip links

Answer 36

Extracellular filaments that physically connect hair cells together. spring gate ion channels (mechanical).

Question 37

Shearing movement of basilar and tectorial membranes

Answer 37

deflect hair cells

Question 38

Tension on tip link filaments leads to

Answer 38

opening of the ion channels

Question 39

The base of each hair cell is

Answer 39

contacted by a process from one or more spiral ganglion cells.

Question 40

the somas of the ganglion cells are in

Answer 40

the center of the cochlea, and the axons form the auditory nerve (8th cranial pair)

Question 41

monoaural pathway

Answer 41

recognition of sound (what). anterior auditory pathway to prefrontal cortex.

Question 42

binaural pathway

Answer 42

localization of sound (where). requires computation of differences between both ears in time of arrival and sound intensity. posterior auditory pathway to posterior parietal cortex.

Question 43

Cochlear nucleus and olives are in the

Answer 43

myelencephalon.

Question 44

The head absorbs sound energy

Answer 44

so that sound intensity is greater in one side of the head than on the other

Question 45

The brain is also sensitive to

Answer 45

millisecond differences in arrival time between the ears

Question 46

The lateral and medial superior olives react to

Answer 46

differences in what is heard by the two ears

Question 47

Medial olives

Answer 47

compute arrival time differences

Question 48

lateral olives

Answer 48

compute amplitude differences

Question 49

of areas in primary auditory cortex

Answer 49

two or three (tonotopic)

Question 50

of areas in secondary auditory cortex

Answer 50

about seven areas (tonotopic). do not respond well to pure tones and have not been well-researched.

Question 51

Functional columns

Answer 51

cells of a column respond to the same frequency

Question 52

Lesions of auditory cortex in rats results in

Answer 52

few permanent hearing deficits

Question 53

Lesions in monkeys and humans hinder

Answer 53

sound localization and pitch discrimination

Question 54

total deafness is rare due to

Answer 54

multiple pathways

Question 55

conductive deafness

Answer 55

damage to the ossicles

Question 56

nerve deafness

Answer 56

damage to the cochlea. Partial cochlear damage results in loss of hearing at particular frequencies.

Question 57

echolocation in bats

Answer 57

doppler shifts in frequency