Psych 267 Chapter 12

Front 1

Auditory localization

Back 1

Is the ability to locate the source of sounds within auditory space. We typically examine how people can locate sounds on one of three planes. 1. Azimuth - left to right 2. Elevation - up and down 3. Distance - from the listener.

Front 2

Visual vs. Auditory localization

Back 2

The image on the retina contains spatial information. Different frequencies of sound are coded at different points on the basilar membrane, but no spatial information.

Front 3

Sound location cues

Back 3

Because the cochlea contains no spatial information about sounds, we must use location cues.

Front 4

Binaural cues

Back 4

Cues that can be derived from sound information arriving at both ears. 2 primary ones, ITD, and ILD.

Front 5

Interaural time difference (ITD)

Back 5

Is based on the fact that there can be differences in the time it takes a sound to arrive at one ear compared to the other. Effective for lower frequency sounds. Uses differences in time of arrival. Relies on signal arrival time via phase locking.

Front 6

Interaural Level difference (ILD)

Back 6

Is based on the difference in sounds pressure levels reaching the two ears. Works well for high frequency sounds. Is accomplished using intensity differences. The head creates an acoustic shadow which causes differences in intensities that are detected by the two ears.

Front 7

Localization of continuous sounds

Back 7

To localize continuous sounds we can use phases differences in the two eardrums. Works well for low to mid-frequency sounds.

Front 8

Sound elevation and the cone of confusion

Back 8

ITD and ILD work well for left and right localization, however they provide little information about elevation. Cone of confusion.

Front 9

Cone of confusion

Back 9

Refers to a region where the ITD and ILD will be identical.

Front 10

Monaural spectral cues

Back 10

Used in order to detect changes in elevation. Created by reflections from the pinna.

Front 11

Detecting elevation differences

Back 11

Different parts of the pinna cause different patterns of sound reflection, Direct vs. reflected sound. Sounds from different locations have different spectral patterns, differences in timbre.

Front 12

Detecting elevation differences. Exp.

Back 12

Hoffmann et al., fitted participants ears with moulds that altered the sound reflection characteristics of the pinna. Initially subjects performed poorly at determining the elevation of the sound. After a number of days the auditory system adapted to the new configuration. After the mould was removed, performance rapidly returned to baseline.

Front 13

Human echolocation

Back 13

Bats are able to use echolocation to navigate and to detect prey in the environment. Daniel Kish has been blind from the age of 13 months and has no visual memories. He successfully trained himself to locate and recognize objects in the environment using the echoes from clicks that he generates.

Front 14

Physiology of sound location

Back 14

How and where does the brain compute ITD and ILD? Coincidence detectors in the medial superior olive. Tuned to different ITDs, medial superior olive. Also tuned to different ILDs, lateral superior olive.

Front 15

Coincidence detectors in the superior olive

Back 15

Neurons in the medial superior olive are tuned to different ITDs, Work better for low frequencies. 'Coincidence detectors' fire when inputs from both ears arrive at the same time, Sounds located directly ahead arrive at both ears simultaneously. Sounds from one side will lead and travel further along the pathway before meeting the signal from the other ear.

Front 16

Detecting intensity differences

Back 16

Neurons in the lateral superior olive respond to intensity differences between the two ears, Works best for high frequencies. EE neurons - give a stronger response to binaural stimulation. EI neurons - respond more as intensity increases in the contralateral ear.

Front 17

Auditory scene

Back 17

Is the array of sound sources in your immediate environment.

Front 18

Auditory scene analysis

Back 18

Is separating each sound into discrete perceptions

Front 19

Onset time

Back 19

Sounds that start at different times are usually generated by different sources.

Front 20

Location

Back 20

Sounds coming from a distinct source usually originate from one position, or a slowly moving position.

Front 21

Similarity of timbre and pitch

Back 21

Sounds that have the same timbre or pitch range are usually produced by the same source

Front 22

Auditory stream segregation

Back 22

The ability to separate different sound sources.

Front 23

Auditory continuity

Back 23

Sounds that stay constant or change smoothly are usually produced by the same source. Auditory stimuli with the same frequency are perceived as continuous even when they are interrupted by another stimulus.

Front 24

Hearing inside rooms

Back 24

The path the sound travels to reach our ears can vary dramatically depending on the listening environment. Direct vs. indirect sound.

Front 25

Precedence effect examples

Back 25

If two tones are presented in separate speakers separated by a 100+ ms, we perceive two sources.If tones are presented in separate speakers with a very short delay, we perceive the source as the 'lead' speaker.

Front 26

Precedence effect definition

Back 26

Is when we perceive the source as being the one that reached our ears first.

Front 27

Architectural acoustics

Back 27

examines how sounds are reflected in rooms. The reflection of indirect sounds is influenced by the amount of sound absorbed by the ceiling, walls, floor. The size and shape of the room.

Front 28

Reverberation time

Back 28

The time it takes for a sound to decrease to 1/1000th of its original pressure. If the R time is too short, the sound is flat. If the R time is too long, the sound is muddled. The ideal R time for a concert hall is 2 sec.

Front 29

Intimacy time

Back 29

Time between when the sound arrives directly from the stage vs. when the first reflection arrives.

Front 30

Bass ratio

Back 30

The ratio of low to middle frequencies that are reflected from surfaces.

Front 31

Spaciousness factor.

Back 31

The fraction of all sound received by the listener that is indirect sound.