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A nonlinear dynamical systems analysis of fricative consonants
1Department of Electrical Engineering, UCLA 90024, USA.
The Journal of the Acoustical Society of America
|April 1, 1995
Summary
This study analyzed acoustic waveforms of American English fricatives and vowels using chaotic analysis. Some fricatives exhibited low-dimensional chaotic dynamics, unlike vowels, suggesting complex production mechanisms.
Area of Science:
- Phonetics and Acoustics
- Nonlinear Dynamics and Chaos Theory
- Speech Production and Perception
Background:
- Strident fricatives (/s/, /z/, /integral of/, /3/) are crucial in speech, characterized by turbulent airflow.
- Previous research suggests complex dynamics in speech production, but detailed analysis using chaos theory is limited.
- Understanding the acoustic properties of fricatives can elucidate their articulatory and aerodynamic underpinnings.
Purpose of the Study:
- To investigate the presence and characteristics of low-dimensional chaotic dynamics in American English strident fricatives.
- To compare the dynamic behavior of fricatives with that of vowels (/a/, /i/, /u/).
- To interpret acoustic findings in relation to articulatory and aerodynamic models of fricative production.
Main Methods:
- Analysis of acoustic waveforms of fricatives and vowels from two native American English speakers.
- Application of modern chaotic analysis techniques, including correlation dimension (D2) and maximum Lyapunov exponents (LEs).
- Extraction of data from both intervocalic and sustained utterances, with attention to stationarity requirements.
Main Results:
- Low-dimensional chaotic dynamics were detected in 44% of unvoiced fricative tokens (VCV) and 59% of sustained voiced fricatives.
- Chaotic behavior was quantified by correlation dimensions (D2) between 3 and 7.2, and positive maximum Lyapunov exponents (LEs).
- Vowel analysis indicated nonchaotic behavior, consistent with prior studies, showing folded limit cycles and nonpositive LEs.
Conclusions:
- A significant portion of strident fricatives exhibit low-dimensional chaotic dynamics, suggesting complex, nonlinear processes in their production.
- The findings differentiate the dynamic complexity of fricatives from the more predictable behavior of vowels.
- Results support the interpretation of fricative turbulence as a manifestation of underlying articulatory and aerodynamic instabilities.