Perceptual Closure

Question 1

Damenbring (1976) - Continuity Illusion

Answer 1

• an example of auditory perceptual closure
• tonal glides are perceived as continuing through a masking sounds
• the auditory system uses information it has from fragments and reconstructs missing parts

Question 2

Masking Rule

Answer 2

• sound ‘B’ must have enough energy in right frequency regions to completely mask sound ‘A’
• results are frequency dependant, so the closer in frequency the sound gets to masker, the louder the faint tone must be to break illusion of perceived continuity

Question 3

No Discontinuity Rule

Answer 3

Bregman & Dannenbring (1977) - there must be no other cues to suggest that there was a silence in A
- onset/offset must be completely masked for illusion of perceived continuity

Question 4

Good Continuation Rule

Answer 4

• sound emerging from masker has to be similar enough for perceived continuity
• Bregman et al (1999) > bigger the frequency separation, the more segregation. The faster the sequence, the less continuity and the wider the bandwidth, the less continuity

Question 5

Haywood, Chang & Ciocca (2011)

Answer 5

• putting a silent gap in the middle of the masker does not break perceive continuity
• this indicated that junctions between the sound and masker are what is important for perceived continuity

Question 6

Perceptual restoration of speech sounds

Answer 6

• if interrupted speech is filled with masker, you get perceived continuity

> Phonemic restoration: listeners are poor at judging exactly which speech sounds have been replaced by interrupter, and interrupted sound is not perceived at replaced
- involves schema-based processes > knowledge about language, not just grouping principles

Question 7

Warren et al (1969)

Answer 7

• speech is a rapidly changing/dynamic and acoustically diverse signal
• listeners cannot accurately judge order of a series of diverse sounds played rapidly because it is heard as single coherent stream
• this would suggest that when listening to speech we are unable to judge the order of phonemes, given their dynamic and acoustically diverse nature, however we know this is not true.

Question 8

Darwin & Bethell-Fox (1977) - Pitch Contours

Answer 8

• pitch contours = contour generated by vocal cord
• in normal speech, pitch contour is not abrupt, and when it is you get segregation
• introduced abrupt changes to pitch which we know trigger segregation, this also changed what consonants were heard
• perceived silence due to stream segregation causes lower pitch stream to sound like stop consonants
• therefore smooth pitch contours are critical in holding together speech

Question 9

Cole & Scott (1973) - Formant Transitions

Answer 9

formant transitions = resonance of vocal tract which represent changes in shape of jaws, lips, tongue which move smoothly
- found that removing transitions led to more segregation highlighting their role in holding speech together

Question 10

Bird & Darwin (1998) - Noise vocoded and Sine wave speech

Answer 10

• sine wave speech > formats separated to create pure tones
• noise vocoded speech > natural speech separated into frequency bands, amplitude envelopes removed
• key acoustic cues for natural speech are pitch contours and formant transitions which are removed in modified speech, making it difficult to understand
• however introducing differences in F0 makes it easier to separate
• indicates that grouping by harmonic relations is important in separating concurrent voices

Question 11

Mesgrani & Chang (2012)

Answer 11

• investigated role of attention in epilepsy surgery patients using electrodes to record cortical activity
• converted into speech spectrograms and found that most prominent features in spectrograms were of the voice that was attended to (either male or female)
• suggests that when attention is directed, level of interferer is turned down and that differences in F0 likely to lead to grouping cues