Topic 9: Hearing

Question 1

sound

Answer 1

physical phenomenon
pressure changes in air or another medium
caused by vibrating object

Question 2

condensation

rarefaction

Answer 2

air molecules are pushed together
air molecules are spread out
alternating patterns of compressed and non-compressed air

Question 3

pure tones

complex tones

Answer 3

generated by tuning for or computer
sound is described by set of pure tones
can be made by summing pure tones, tones represented by frequencies not time

Question 4

sine wave
frequency
amplitude

Answer 4

• sinusodal cahnge in air pressure
• number of cycles per second (Hertz)
• magnitude of air pressure changes (dB), 20 x log`

Question 5

spectrogram

white noise

Answer 5

calculate energy at each frequency, straight lines are same frequency at each time point
red = high energy black = no energy
-random frequencies that change randomly, evenly dispersed over spectrogram

Question 6

loudness

threshold of feeling

Answer 6

perceptual quality most closely related to level or amplitude of auditory stimulus

• loudness will vary with frequency
• hearing is painful, small but noticeable frequency differences

Question 7

pitch

Answer 7

perceptual quality we describe as high and low

pitch is related to fundamental frequency

Question 8

tone height

tone chroma

Answer 8

generally goes up with fundamental frequency

notes whose fundamental freuqnecy are multiples of 2 have same chroma (high and low C)

Question 9

timbre

Answer 9

quality of sound

difference between 2 tones that have same loudness and pitch but sound different - 2 instruments

Question 10

shepard-risset glissando

constant spectrum

Answer 10

• continuously goes down

- perceptually changes but frequencies are stable, closely spaced harmonics

Question 11

pinna
auditory canal
eardrum
OUTER EAR

Answer 11

• helps focus sound towards ear canal (direction of sound)
• protects ear drum, enhances frequencies of 1000-5000 hz due to resonance
• transmits sound as vibration to middle ear

Question 12

middle ear

MIS

Answer 12

sound pressure changes causes eardrum vibration

malleus = hammer incus = anvil stapes = stirrup

Question 13

middle ear purpose and mechanisms

Answer 13

• amplifies sound by a factor of 10-50 from air pressure in outer ear to liquid pressure in inner ear
• concentrates pressure from large eardrum to small stapes footplate

Question 14

middle ear muscles

stapedius

Answer 14

• tensor tympani

- contracts to mute movement of tapes so auditory system isnt overwhelmed

Question 15

semicircular ducts

cochlea

Answer 15

involved in balance and eq

coiled structure and contains sensory receptors for sound

Question 16

basliar membrane

tip links

Answer 16

sounds transmitted to auditory nerve, pressure waves in cochlea cause baslia membrane to move up and down

• bends cilia and causes ion (K+) channels to open, transduction
• Right = open, left = close

Question 17

phase locking

Answer 17

movement of cilia follows changes in pressure

neurotransmitter release follows changes in pressure

Question 18

place theory

Answer 18

location with peak displacement has highest firing rate by auditory nerve cells
location of max firing indicates frequency
percieved tone is based on where activity is along length of cochlea

Question 19

cochlear amplifier
frequency representation
frequency tuning curve

Answer 19

outer hair cells change shape based on sound and amplify/focus motion of basliar membrane

• sound causes waves to travel along basliar membrane (closer to base for higher frequency)
• each auditory nerve cell responds to certain frequencies based on cochlear position

Question 20

effect of missing fundamental

amplitude modulation

Answer 20

• pitch of C is same as A even without fundamental, no longer peak activity at same place despite same perceived pitch
• fluctuating amplitude of sound at a specific frequency, changes pitch perception despite same frequency of sound

Question 21

temporal theory

Answer 21

timing or repetition rate of a sound is available even when fundamental is missing and with amplitude modulation
leads to phase locking

Question 22

auditory pathway

ACSIMA1

Answer 22

auditory nerve
cochlear nuclei - medulla
superior olivary nucleus - pons
inferior colliculus - midbrain
medial geniculate nucleus - thalamus
primary auditory cortex (A1)

Question 23

external components cochlear implant

Answer 23

-microphone - transduces sound into electricity
-processor- analyzes sound into frequency bands, stimulates place specific activation of basliar membrane
transmitter- sends signals and power

Question 24

internal components cochlear implant

Answer 24

• receiver - receives signals and power

- electrodes - stimulate different auditory nerves along length of cochlea