Listening

Question 1

where do the initial stages of acoustic analysis happen?

Answer 1

superior temporal cortex

Question 2

where does speech processing split into two streams

Answer 2

after inital cortical stages of acoustic analysis speech processing splits into ventral (speech recognition) and dorsal (speech perception) pathways

Question 3

what is speech recognition

Answer 3

temporal regions of the brain map sound onto meaning (ventral processing stream)
lexical

Question 4

what is speech perception

Answer 4

parietal/frontal regions map sound onto action (dorsal processing stream) phonological

Question 5

what does the dual processing stream model predict

Answer 5

that damage to the ventral stream will impair comprehension while damage to the dorsal stream will impair processing repetition of speech sounds

dissociation between performance on auditory comprehension tasks and sub-lexical perception tasks
e.g unable to distinguish cat and cot but can appropriately match these to pictures

parallel pathways with some crosstalk

Question 6

what is the segmentation problem

Answer 6

how are we able to perceive speech when there are few gaps in words visible in a waveform of a speech signal

e.g perceived gaps are difficult to identify within a waveform or spectrogram as there are no clear boundaries in a continuous stream yet we are able to break it down into words, syllables and phonetic features

thus there is no direct correspondence between auditory energy and perception (no correlation of amplitude and gaps)

Question 7

how can we identify vowels in a spectrogram

Answer 7

the relative spacing of steady state portions of a spectrogram

Question 8

how do we perceive speech

Answer 8

the continuous speech signal is perceived as segments
25-50 phonetic segments per second (4-5 syllables)
speech sounds should be identifiable by different combinations of formant frequencies and the shapes of these transitions

Question 9

what information is there in a spectrogram

Answer 9

the frequencies of sounds produced over time
formants: bands of acoustic energy
steady state: vowel identity
transitions: consonant identity

Question 10

what is meant by ‘steady state’

Answer 10

the steady state ratio of the first and second formant distinguishes vowels

Question 11

what is meant by formant transitions

Answer 11

correspond to production of constant

second formant anticipates the frequency of the vowel that will be produced next

Question 12

what is coarticulation

Answer 12

the features that characterise speech sounds occur non-linearly
we produce them in parallel rather than in sequence

anticipating what next production will be is reflected in production of a sound

overlap of movements in phoneme production

makes speech production fast and efficient, but means spectrogram will be different depending on the context of the following vowel etc

Question 13

what are the problems for speech perception

Answer 13

non-linearity
lack of invariance
speaker variability

Question 14

what is meant by non-linearity

Answer 14

acoustic features spread themselves across each other and are not procured as a linear sequence

Question 15

what is meant by the lack of invariance

Answer 15

speech sounds have more than one waveform representation
the differences between phonemes are very small
there are big differences between different instances of the same phoneme
coarticulation exists whereby the articulation of one phoneme influences that of another

Question 16

how are the problems of speech perception solved

Answer 16

by perceiving a range of sounds categorically

Question 17

what is categorical perception

Answer 17

despite the lack of invariance in the acoustic signal we still perceive specific categories that correspond to phonemes (the smallest units of sound which change the meanings of words)

speech perception is categorical as the variation within phonemes is contained in a single category

Question 18

given categories can’t vary infinitely, what tasks have psychologists designed to better understand the nature of categorical perception?

Answer 18

Voice onset time e.g ga released same time as vocal chords start vibrating whereas ka has a much later voice onset time despite benign produced in the same place
Wig vs wick
Artificial speech syllables

Question 19

how is voice onset time a continuum

Answer 19

changing the time of consonant release alters the percept

this can happen for both the sound at the start or end e.g ba - ka and wig-wick

Question 20

what does a place of articulation continuum show

Answer 20

difference between ba and da is place of articulation
this is represented in the slope of the formant (usually second)
changing this incrementally produces a continuum

Question 21

what happens in categorical perception of speech

Answer 21

hallmarks: identification and discrimination tasks

identification tasks e.g on ba-da continuum produce steep sigmoidal slope characteristic of categorical perception

discrimination task: boundary established with identification task and take stimulus pairs (either same or different side of boundary: cross or within category pairs) - same acoustic unit range each time, asked if they are the same or different - looking for a peak in the discrimination function to demonstrate categorical perception (note this isn’t seen for non-speech sounds, we’re better at discriminating notes on a piano etc)

speech is special