auditory perception Flashcards

Question

place coding at different frequencies

Answer 1

less reliable at low frequencies areas of vibration on BM bigger at lower frequencies less specific and precise encoding of pitch

Answer 2

breaks down at high frequencies not enough time for cells to recharge leads to temporal smearing peaks happening too close for coding to work firings overlap and brain doest know which firings correspond to which peak of waveform

Answer 3

detect motion of basilar membrane ion flow causes electrical signals to brain

Answer 4

amplify and sharpen motion of basilar membrane = cochlear tuning means we have good ability to discriminate different pitches ion flow causes mechanical changes expand and contract motions amplify and sharpen basilar membrane action = more precise

Answer 5

pitch represented by 2 mechanisms: place coding = where on the BM firing comes from temporal = when the firing is occurring timbre represented by which combinations of fibres are active at the same time

Answer 6

relies on the fact that there are low and high threshold auditory nerve fibres low threshold fibres discriminate quiet and moderate sounds - discriminate between low and medium amplitude sounds high threshold fibres kick in to discriminate moderate and loud sounds - discriminate between moderate and high amplitude sounds loudness of sound = total neural activity loud sound means all fibres are responding, quiet sounds mean only low responding

Answer 7

starts with cochlear sent through auditory nerve to cochlear nucleus - acts as a relay station - send neural activity to other nuclei in brainstem then travels through superior olive - analyses location, where sounds are coming from - relies on precise timing so happens early then to inferior colliculus and medial geniculate - analyse pitch - relies on fairly precise timing, not quite as early as location processing ends in primary auditory area - analyses higher order features, such as timbre - less reliant on precise timing

Answer 8

cochlear nucleus superior olive inferior colliculus medial geniculate primary auditory cortex

Answer 9

whether sound is coming from the left or right

Answer 10

sound from one side reaches that side first eg left reaches left first allows brain to detect direction sound is coming from brain very sensitive to these small differences in time

Answer 11

if sound coming from left, right is shielded by the head sound arrives at far ear later arrives there quieter than other side when sound directly from side, ILD depends on the frequency

Answer 12

to use ITDs, need to be able to match specific peaks in sound waves across both ears at higher pitch = shorter wavelength harder for brain to determine whether left or right came first misinterprets where peaks are relative to each other ITDs ambiguous or misleading at higher frequencies

Answer 13

sounds diffract and bends around object smaller than its wavelength sound blocked by larger objects low frequencies diffract around the head - some sound reaches far ear - got there later but at a similar frequency high frequencies do not diffract - creates a head shadow - limited sound at the far ear - creates a larger ILD ILDs only useful at higher frequencies

Answer 14

ITDs and ILDs don't help pinnae do amplify some frequencies and reduce others create spectral cues by changing incoming frequency spectrum change the timbre complex waveforms represented as different component frequencies represented on a spectrum when sounds come from different heights shape of ears filter sounds in different ways - creates different timbres depending on elevation of noise = unique resonance patterns according to height

Answer 15

sound from directly in front or behind = ITD of 0 - takes just as long for sound to get to ears from front as back - equally as loud pinnae create small level differences we can also rotate our heads

Answer 16

axons transmitting electrical signals representing sound from both ears - acts as delay lines axons connected to neurons - act as neural coincidence detectors means neurons only fire when stimulated at same time by information from left and right ear measuring using ITD tuning curves look at different neurons and measure firing rate across different ITDs curve supports this model for some animals - terrestrial more likely to use opponent process analysis

Answer 17

sound waves from straight ahead come in from both ears travels along until both left and right ears reach and feed into same neuron at same time - then fires this specific neuron during allows the brain to know that the sound in coming from directly in front if sound comes from right, hits right ear first signal comes in from right before left left stimulated later than right sounds reach neuron together causing it to fire different specific neruon fired - allows brain to determine that it is from an angle

Answer 18

involves 2 sets of broadly tuned neurons neurons tuned to left half of auditory space - in right hemisphere neurons tuned to right half of auditory space - in left hemisphere system calculates the difference between the two sets to work out where a sound is coming from - if most firing from left half, assume sound from left and vice versa - smaller differences mean closer to centre - no difference, assume sound straight infront

Answer 19

vibrations from the larynx travel upwards through vocal tract spectrum of sound is shaped by the articulators including: - soft palate, hard palate, tongue, teeth and lips and the resonant spaces (resonators) including: - chest, throat, mouth and nasal cavities larynx (voice box) contains folds of material air forced from lungs through fold, making them vibrate - vibrations create sounds

Answer 20

speech perception relies on more than the acoustic signal also reels on both top down (cognitive) and bottom up (perceptual) factor

Answer 21

sounds made by forcing air through narrow gap in articulators eg s, sh, z a lot of energy through lots of frequencies but particularly in high frequencies shown by dark bands

Answer 22

articulators can be used to shape our vocal tracts creates vowel sounds shown by stripy bands at lower frequencies peaks in spectrum - frequency components in vowel sounds that are particularly strong

Answer 23

the same sound is actually different depending on the acoustic context (neighbouring sounds) however we perceive these as being the same known as perceptual constancy reflects to down contribution of articulatory knowledge know what is needed to make these sounds so can remove small perceptual difference

Answer 24

perceptual illusion visually presented sounds affect perception of the acoustic signal use of visual information inform interpretation of articulatory knowledge

Answer 25

our perception of speech sounds is affected by the meaning of the context

Answer 26

if a familiar word is distorted (eg a missing sound) we put it back in without realising influence of lexical knowledge

Answer 27

perception of speech sounds is affected by the meaning od the context normal sentences grammatical string of words played people these sentences and asked to repeat them back - all sentences should have been equally intelligible but intelligibility decreased as stimuli became less meaningful or grammatical correct shows influence of semantic and syntactic knowledge - regardless of quality of acoustic inputs - contextual knowledge of linguistic factors essential for perception

Answer 28

formants replaced with pure tones tracking the intensity modulations of those formants over time sine wave speech can be learnt has no fricative sounds etc only formants but due to formants and coarticulations can be learnt (formants influence perception of surrounding speech) shows influence of phonological, lexical and syntactic and semantic knowledge