week 9 (auditory)

Question 1

question: what’s the most common and serious form of hearing loss?

Answer 1

• sensorineural
• damage of hair cells or auditory nerve
• permanent bc hair cells don’t regen.

Question 2

define: prebycusis

Answer 2

• hearing loss that occurs gradually due to effects of aging
• initially loses high freq. sounds but eventually even regular sounds are hard to hear

Question 3

question: why does sound sound louder in bone conduction test (when touching bone)?

Answer 3

• bc bone is being vibrated aka cochlea
• bypasses outer and middle ear
  ⤷ bypasses any possible damage to structures

Question 4

explain: hearing aids

Answer 4

• mini amplifier that fits in auditory canal or behind ear
• small microphone collects sound
  electronic amplifier
• small speaker to deliver sound to hear
• best if cochlear fucntion isn’t damaged

Question 5

define: audibility threshold

Answer 5

• lowers sound psi level that can reliably be detected at a given freq.

Question 6

question: minimum audible field vs pressure thresholds?

Answer 6

FIELD
- measures hearing thresholds in a free field (using loudspeakers)
- sound reaches both ears naturally

PRESSURE
- measures hearing thresholds through headphones or earphones,
- sound delivered to one ear at a time

Question 7

name: pros and cons of MAF and MAP

Answer 7

MAF
- PRO = realistic, binaural, lower thresholds
⤷ better sensitivity
- CON = expensive and time consuming, hard to calibrate a field

MAP
- PRO = no envrt. factors, easier to calibrate, easier to standardize
- CON = unnatural, lack binaural stim.

Question 8

explain: audibility curve (terminal threshold?)

Answer 8

• graphing freq. on x against sound level on y
• lowest detection threshold = minimal audibility curve
• terminal threshold = upper limit of aud. func.
• rea in between = dynamic range of human hearing

Question 9

define: ultrasonic and infrasonic

Answer 9

• ultra = anything above terminal threshold
• infrasonic = anything below minimal audibility

Question 10

question: why can we “feel” lower freq. sounds?

Answer 10

• the long sound wave period can go through body

Question 11

explain: equal loudness curves

Answer 11

• many lines on graph
• x = freq., y = sound level
• obtained by asking listeners to equate loudness of sounds with diff. freq.
• on the same line = perceived as the same loudness but not same intensity

Question 12

name: factors that affect absolute sensitivity (3)

Answer 12

1. method of data collection
   ⤷ MAP over MAF
2. monaural vs binaural
   ⤷ monaural stim. has thresholds higher
   ⤷ binaural summation
3. masking
   ⤷ presence of white noise on sensitivity
   ⤷ having white noise increases the threshold

Question 13

explain: missing fundamental effect

Answer 13

• can play a harmonic series and remove the corresponding fundamental freq. and still hear it
• reason = phase locking
• all the harmonics fire at regular internals
  ⤷ phase locked in regular cycles that follow the OG fundamental -> sounds like fundamental is still there
• ex. all graphs peak in same spot -> cumulative

Question 14

define: timbre

Answer 14

• perceptual quality that allows us to distinguish musical instruments
• everything else about a sound other than loudness and pitch

Question 15

define attack and decay

Answer 15

• attack = the way a sound starts
• decay = the way a sound ends

Question 16

explain: spectrogram

Answer 16

• x = time
• y = freq.
• more red = more intense
• more blue = less intense

Question 17

question: how do we describe physical location of a sound?

Answer 17

• azimuth = horizontal plane
• elevation = vertical plane

Question 18

question: diotic stim. vs dichotic stim.?

Answer 18

DIOTIC
- sound right in front or right behind
- sound reaches ear around the same time and intensity

DICHOTIC
- off to one side -> diff. in sound quality between ears

Question 19

define: interaural time difference?

Answer 19

• relevant only for dichotic sounds
• less susceptible to freq. so can be used for all freq.
• graph x = direction of source
• graph y = interaural time diff.

Question 20

explain: cones of confusion

Answer 20

• hard to determine location of sound bc need to consider elevation and azimuth
• falls in cone of confusion
  ⤷ can’t tell if front vs behind
• solution: move head
  ⤷ only one location will be consistent with ITD and ILD

Question 21

question: where does binaural integration happen?

Answer 21

• above cocholear nucleus
• first spot is superior olive
  ⤷ area of sound localization bc need binaural info to compare
  ⤷ has medial and lateral divisions

Question 22

explain: how does the medial superior olive compute sound location using interaural time difference?

Answer 22

• slight time diff. between ears for when wave reaches vibrates basilar mem.
• delay lines = axons of neurons varying in length to makeup for time diff.
• ex. sound coming from L
  ⤷ sound reaches L ear first
  ⤷ AP travels to MSO and takes longer path bc delay lines
  ⤷ sound reacehs R ear and AP to MSO
  ⤷ meets the L into at the left earleading neuron
  ⤷ sends coincident info and signals sound coming from L

Question 23

name: reasons for interaural level difference (intensity diff.)

Answer 23

• sound psi decreases with distance
• head shadow effect
  ⤷ does work for lower freq. bc longer wavelengths
  ⤷ will bend around head and reach earss at same time

Question 24

question: how does lateral superior olive compute sound location with interaural intensity diff.?

Answer 24

• stronger stim. for L ear excites L LSO + inhibits R LSO
• ipsilateral = excitatory, contralateral = inhibitory
• ON LEFT SIDE: excitatory of L = greater than inhibition of R -> net excitation
• ON RIGHT SIDE: inhibition from L = greater than excitation of R -> net inhibition

**inhibition and excitation cancel each other out at 0

Question 25

recap: which superior olive uses IIDs vs ITDs?

Answer 25

- median superior olive = ITDs - lateral superior olive = IIDs

Question 26

name: ways to gauge auditory distance perception (3)

Answer 26

1. **relative intensity** - closer sounds = louder 2. **spectral composition** - sound absorbing qualities of air dampens higher freq. 3. **relative amount of direct and reverberant energy** - closer source = most of the E reaching the ear is direct

Question 27

explain: spatial hearing and blindness

Answer 27

- severe loss of vision can improve localization of sounds - occipital cortex gets recruitedto process auditory input - some canlearn to echolocate

Question 28

define: auditory scene analysis

Answer 28

- distinction of auditory events in broader auditory envrt. - ability to follow one sound despite surrounding noise - sounds perceived as being part of the same source = same auditory stream

Question 29

explain: how the ASA works

Answer 29

- spatial segregation ⤷ sounds that emanate from same location likely come from same source - spectral segregation ⤷ sounds with similar pitches = treated as same source - temporal segregation ⤷ sounds that occur together are grouped together

Question 30

explain: gestalt principles and timbre

Answer 30

- humans tend to group similar elements, patterns - sounds sharing same timbre are grouped based on freq. - but diff. timbres -> separate according to timbre - perceptual restoration ⤷ like to listen to intact sound in the presence of noise - common fate ⤷ sounds that begin at same time = tend to be perceived as coming from same source

Question 31

explain: gestalt's proximity and familiarity for audition

Answer 31

- grouping by repetition (proximity) ⤷ sounds that repeat over time = same source - grouping by familiarity ⤷ listeners make use of experience and familiarity to separate sources

Question 32

explain: acoustic startle reflex

Answer 32

- very fast motor resp. to sudden loud sound - musc. twitches - unselective (any sound can work) - being scared increases the resp.

Question 33

define: inattentional deafness

Answer 33

- failure to notice fully audible but unexpected sound bc attention was on another stream of aud. **listeners = less accurate at understanding what they heard when switching between 2 streams