chapter 12

Question 1

auditory space

Answer 1

perception of where sounds are located in space - auditory space extends around a listener’s head in all directions, existing wherever there is a sound

Question 2

auditory localization

Answer 2

the locating of sound sources in auditory space

Question 3

location cues

Answer 3

information created by the way sound interacts with the listener’s head and ears. the auditory information uses this information to determine location

Question 4

what are the two types of location cues

Answer 4

binaural cues: depend on both ears

spectral cues: depend on just one ear

Question 5

what are the three dimensions of sound position

Answer 5

azimuth: extends from left to right
elevation: extends up and down
distance: from the sound source to the listener (least accurate and works best when the sound source is familiar, or when cues are available from room reflections)

Question 6

two types of binaural cues

Answer 6

interaural level difference and interaural time difference

Question 7

interaural level difference

Answer 7

based on the difference in the sound pressure level of the sound reaching the two ears

Question 8

acoustic shadow

Answer 8

the head acts as a barrier causing a difference in sound pressure level between the two ears, reducing the intensity of sounds that reach the far ear

Question 9

when does the acoustic shadow occur

Answer 9

intensity is reduced in the far ear at high frequency sounds (greater than about 3000Hz for humans), but not for low frequency sounds

Question 10

why does an interaural level difference occur for high frequencies but not for low frequencies?

Answer 10

because high frequency sounds have small spacing between them, meaning they are stopped by the head - whereas, low frequency sounds have large gaps in spacing, larger than the head, so are not affected

Question 11

interaural time difference

Answer 11

the time difference between when a sound reaches the left ear and when it reaches the right ear

becomes larger as sound sources are located more to one side, and its magnitude can be used as a cue to determine a sound’s location

Question 12

when is interaural time difference most effective

Answer 12

most effective at determining the locations of low frequency sounds

this makes it the dominant binaural cue because most sounds in the environment contain low frequency components

Question 13

cone of confusion

Answer 13

an area extending from the ear that looks like a cone. sounds originating from different locations in this general area all have the same interaural level difference and interaural time difference, so location information provided by these cues is ambiguous

Question 14

spectral cues

Answer 14

cues in which information for localization is contained in differences in the distribution of frequencies that reach each ear from different locations

caused by the fact that before the sound stimulus enters the auditory canal, it is reflected from the head and within the various folds of the pinnae

Question 15

evidence for the pinae in determining elevation

Answer 15

when the inside contours of the pinnae are changed with a mold, localization for elevation coordinate is poor, but locations can still be judged along the azimuth coordinate

however, localization performance for elevation improves over time as people get used to the molds and is still good once molds come out (don’t have to readjust themselves)

Question 16

jeffress model

Answer 16

proposes that neurons are wired so they each recieve signals from the two ears

coincidence detectors fire when signals from the left and right ears reach the neuron simultaneously - dif coincidence detectors fire to dif values of interaural time dif

itd is indicated by which itd neuron is firing

Question 17

ITD Detectors

Answer 17

interaural time difference detectors - neurons in the jeffress model that fire when signals reach them from the left and right ears and are tuned to respond to a specific time delay between the two signals = information about possible locations of a sound source

ITD is indicated by which ITD neuron is firing

Question 18

binaural localization in birds vs mammales

Answer 18

sharply tuned in birds: place code bc ITD id indicated by firing of neurons at a specific place in the nervous system

broadly tuned in mammals: population code bc ITD is determined by the firing of many broadly tuned neurons working together

Question 19

superior olivary nucleus

Answer 19

first place that receives signals from the left and right ears

Question 20

anterior vs posterior belt areas

Answer 20

two areas on either side of the auditory cortex

anterior: complex sounds/patterns of sounds - the what auditory pathway extends from the anterior belt to the front of the temporal lobe and then to the frontal cortex

posterior: localizing sounds - the where auditory pathway extends from the posterior belt to the parietal love and then to the frontal cortex

Question 21

direct vs indirect sound

Answer 21

direct sound: sound that reaches your ears directly

indirect sound: reaches your ears after being reflected from a surface

Question 22

precedence effect

Answer 22

when two identical or very similar sounds reach a listener’s ears separated by a time interval of less than about 50 to 100ms, the listener ears the first sound that reaches his or her ears

if the sounds are separated by a longer delay, they will hear two separate sounds

Question 23

architectural acoustics

Answer 23

the study of how sounds are reflected in rooms - largely concerned with how indirect sound changes the quality of sounds we hear in rooms

Question 24

reverberation time

Answer 24

the time it takes for the sound to decrease to 1/1000th of its original pressure

if reverberation time is too long: sounds become muddled because the reflected sounds persist for too long/echo

if reverberation time is too short: music sounds “dead” and it becomes more difficult to produce high intensity sounds

Question 25

intimacy time

Answer 25

the time between when sound arrives directly from the stage and when the first reflection arrives - related to reverberation but involves just comparing the time between the direct sound and the first reflection, rather than the time it takes for many reflections to die down

Question 26

bass ratio

Answer 26

the ratio of low frequencies to middle frequencies that are reflected from walls and other surfaces

Question 27

spaciousness factor

Answer 27

the fraction of all the sound received by a listener that is indirect sound

Question 28

auditory scene

Answer 28

the array of sound sources at different locations in the environment

Question 29

auditory scene analysis

Answer 29

process by which the stimuli produced by each source are separated - hard when sounds from different sources are combined into a single acoustic signal

Question 30

simultaneous grouping

Answer 30

the situation that occurs when sounds are perceptually grouped together because they occur simultaneously in time

Question 31

sequential grouping

Answer 31

grouping that occurs as sounds follow one another in time

Question 32

sequential grouping

Answer 32

grouping that occurs as sounds follow one another in time

Question 33

how do we analyze simultaneous grouping?

Answer 33

• location
• onset synchrony (if two sounds start at slightly different times, it is likely that they came from different sources)
• timbre and pitch (sounds that have the same timbre or pitch range are often produced by the same source
• harmonicity ( when we hear a harmonic series we infer that it came from a single source because it is unlikely that several sound sources would create a fundamental and the pattern of harmonics associated with it)

Question 34

how do we analyze sequential grouping

Answer 34

similarity in pitch (consecutive sounds produced by the same source usually are similar in pitch)

auditory continuity (sounds that stay constant or that change smoothly are often produced by the same source) - similar to gestalt principle of good continuation

experience (past experience)

Question 35

auditory stream segregation

Answer 35

the effect that occurs when a series of sounds that differ in pitch or timbre are played so that the tones become perceptually separated into simultaneously occurring independent streams of sound

depends on pitch and the rate at which tones are presented

Question 36

scale illusion/melodic channeling

Answer 36

when successive notes are a scale are presented alternately to the left and right ears smoothly ascending or descending scales are hears in ear ear even though each ear receives note

comes from grouping by similarity creating the illusion of smooth sequence of notes

Question 37

multisensory interactions

Answer 37

use of a combination of senses - an example for vision and hearing is seeing a person’s lips move while listening to the person speak

Question 38

ventriloquism effect/visual capture

Answer 38

example of vision dominating hearing - when sounds coming from one place appear to come from another place

Question 39

two flash illusion

Answer 39

an illusion that occurs when one flash of light is presented, accompanied by two rapidly presented tones - presentation of the two tones causes the observer to perceive two flashes of light

another example of auditory visual interaction

Question 40

speechreading

Answer 40

lip reading - lip movements provide information about what sounds are being produced

Question 41

visual and hearing interactions in the brain

Answer 41

sensory areas in the brain are interconnected - high level of overlap between auditory and visual fields in the brain

Question 42

echolocation

Answer 42

locating objects by listening to the echoes that bounce off them

echolocation can activate visual areas of the brain