PSYB51 Lecture 10: Lecture 10 PSYB51
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Lecture 10: Music and Speech Perception
Hearing in the Environment
- Complex sounds: Missing Fundamentals
- Timbre: Timbre aftereffect, attack and decay
– 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
• 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
– 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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– 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 out” of 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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