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Lecture 10

PSYB51 Lecture 10: Lecture 10 PSYB51


Department
Psychology
Course Code
PSYB51H3
Professor
Matthias Niemeier
Lecture
10

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Lecture 10: Music and Speech Perception
Hearing in the Environment
- Complex sounds: Missing Fundamentals
- Timbre: Timbre aftereffect, attack and decay
• Harmonics
Lowest frequency of harmonic spectrum: Fundamental frequency
Auditory system is acutely sensitive to natural relationships between harmonics
e.g. vowels
Missing-fundamental effect
Missing Fundamental (part 1)
• Missing fundamental (x1) is not/barely noticed.
• More harmonics can be missing.
• How come?
Part 2: Demo in Matlab
Part 3
• Missing fundamental harmonic: 250 Hz
• 2nd, 3rd & 4th harmonic overlap in peaks every 4 ms
• Added up they yield a fluctuation in energy at 250 Hz
• Temporal coding of frequency
Timbre: Psychological sensation by which a listener can judge that two sounds that have
the same loudness and pitch are dissimilar; conveyed by harmonics and other high
frequencies
Perception of timbre depends on context in which sound is heard
Experiment by Summerfield et al. (1984)
• “Timbre contrast” or “timbre aftereffect”
• Summerfield et al.’s (1984) “timbre aftereffect”
• Attack and decay of sound
Attack: Part of a sound during which amplitude increases (onset)
Decay: Part of a sound during which amplitude decreases (offset)
Auditory Scene Analysis
Segregating sound sources

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Grouping
The ventriloquist effect
• What happens in natural situations?
Acoustic environment can be a busy place
Multiple sound sources
How does auditory system sort out these sources?
Source segregation, or auditory scene analysis
Auditory Scene Analysis
• A number of strategies to segregate sound sources
Spatial separation between sounds; motion parallax
Separation on basis of sounds spectral or temporal qualities
Auditory stream segregation: Perceptual organization of a complex acoustic signal into
separate auditory events for which each stream is heard as a separate event
Gestalt law: “similarity”
Gestalt: German for “form”. In perception a term introduced by a school of thought
stressing that the perceptual whole could be greater than the sum of its parts.
• Grouping by timbre
Tones that have increasing and decreasing frequencies, or tones that deviate from
rising/falling pattern pop outof sequence
• Grouping by onset
Harmonics of speech sound or music
Grouping different harmonics into a single complex tone
Rasch (1987) showed that it is much easier to distinguish two notes from one another
when onset of one precedes onset of other by very short time
Gestalt law of common fate
Does the bottle break?
Spectogram: A pattern for sound analysis that provides a 3D display of intensity as a
function of time and frequency
E.g., bouncing/breaking bottle
• Multisensory integration: vision (usually) helps audition
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