The Aeroacoustics of Nasalized Fricatives by Ryan Keith Shosted BA
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The Aeroacoustics of Nasalized Fricatives by Ryan Keith Shosted B.A. (Brigham Young University) 2000 M.A. (University of California, Berkeley) 2003 A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Linguistics in the GRADUATE DIVISION of the UNIVERSITY OF CALIFORNIA, BERKELEY Committee in charge: John J. Ohala, Chair Keith Johnson Milton M. Azevedo Fall 2006 The dissertation of Ryan Keith Shosted is approved: Chair Date Date Date University of California, Berkeley Fall 2006 The Aeroacoustics of Nasalized Fricatives Copyright 2006 by Ryan Keith Shosted 1 Abstract The Aeroacoustics of Nasalized Fricatives by Ryan Keith Shosted Doctor of Philosophy in Linguistics University of California, Berkeley John J. Ohala, Chair Understanding the relationship of aerodynamic laws to the unique geometry of the hu- man vocal tract allows us to make phonological and typological predictions about speech sounds typified by particular aerodynamic regimes. For example, some have argued that the realization of nasalized fricatives is improbable because fricatives and nasals have an- tagonistic aerodynamic specifications. Fricatives require high pressure behind the suprala- ryngeal constriction as a precondition for high particle velocity. Nasalization, on the other hand, vents back pressure by allowing air to escape through the velopharyngeal orifice. This implies that an open velopharyngeal port will reduce oral particle velocity, thereby potentially extinguishing frication. By using a mechanical model of the vocal tract and spoken fricatives that have undergone coarticulatory nasalization, it is shown that nasal- ization must alter the spectral characteristics of fricatives, e.g. by reducing high-frequency energy and increasing the bandwidth of spectral prominences. These spectral modifica- tions are liable to change the percept of fricatives at different places of articulation. It is hypothesized that nasalization generally has a deleterious effect on the acoustic dis- tinctiveness of fricatives, explaining the typological rarity of nasalized fricatives. It also suggests that sibilant fricatives might be better at blocking the effects of nasal harmony. John J. Ohala Dissertation Committee Chair i Contents List of Figures iv List of Tables vi 1 Introduction 1 1.1 The Problem . 1 1.2 Aeroacoustics of fricatives . 4 1.3 Aeroacoustics of nasals . 11 1.4 The Ohalian hypothesis considered . 18 1.4.1 Ohala (1975) . 19 1.4.2 Ohala and Ohala (1993) . 20 1.4.3 Ohala, Sol´e,and Ying (1998) . 21 1.4.4 Yu (1999) . 22 1.4.5 Sol´e(1999) . 23 1.5 Against the Ohalian hypothesis . 24 1.5.1 Schadeberg (1982) . 24 1.5.2 Gerfen (1999, 2001) . 27 1.5.3 Coatzospan overview . 28 Gerfen’s instrumental approach (1999, 2001) . 29 Recommendations . 30 1.6 Strong and weak versions of the hypothesis . 34 1.7 Reports of nasalized fricatives . 35 1.7.1 Applecross Scots Gaelic (Celtic, Scotland) . 35 1.7.2 Chichimeco-Jonaz (Otopamean, Mexico) . 37 1.7.3 Coatzospan Mixtec (Mixtecan, Mexico) . 37 1.7.4 Epena Pedee (Choko, Colombia) . 38 1.7.5 `Igb`o(Niger-Congo, Nigeria) . 38 1.7.6 Icelandic . 39 1.7.7 Inor (Semitic, Ethiopia) . 40 1.7.8 Japanese . 41 1.7.9 Umbundu (Niger-Congo, Angola) . 41 1.7.10 Waffa (Papuan, Papua New Guinea) . 41 1.7.11 Other ‘nasal harmonic’ languages . 42 ii transparent fricative languages . 43 opaque fricative languages . 45 1.8 Summary . 45 2 Method 48 2.1 Research hypotheses . 48 2.2 Methodological overview . 49 2.2.1 Spoken fricatives . 49 2.2.2 Mechanical fricatives . 50 2.3 Languages . 50 2.4 Speakers . 51 2.5 Stimuli . 51 2.6 Spoken data . 53 2.6.1 Audio . 54 2.6.2 Oral flow . 55 2.6.3 Nasal flow . 56 2.6.4 Flow calibration . 57 Procedure . 57 Correlation coefficient . 58 2.7 Mechanical fricatives . 59 2.7.1 Model design . 59 2.7.2 Model data . 61 2.8 Acoustic analysis . 62 2.8.1 Segmentation . 62 2.8.2 Normalization . 62 2.8.3 Zero-crossing rate . 63 2.8.4 Power spectra . 63 Spectral averaging techniques . 64 2.8.5 Parameterization of fricative spectra . 66 High frequency spectral slope (HiSlope) . 68 Low frequency spectral slope (LoSlope) . 68 Slope reference . 69 Dynamic amplitude (DynAmp) . 70 High wide-band frequency energy (HiBand) . 70 Spectral peak bandwidth . 70 2.9 Flow analysis (spoken fricatives) . 70 2.9.1 Segmentation . 70 2.9.2 Normalization . 71 2.9.3 Polynomial fitting . 71 Coefficients . 71 Correlation . 71 Norm of residuals . 72 Statistical evaluation of polynomial fit . 72 2.9.4 Numerical integration . 73 2.9.5 Maximal flow rate and flow rate at temporal center . 75 iii 2.10 Pressure analysis (mechanical fricatives) . 75 2.11 Statistical Methods . 75 2.11.1 Review of variables . 75 Continuous variables . 75 Categorical variables . 75 2.11.2 Null hypotheses . 76 Spoken fricatives . 76 Mechanical fricatives . 76 2.11.3 Linear statistical models . 77 Normality . 77 One-way analysis of variance . 77 2.11.4 Non-linear models: Kruskal-Wallis . 78 3 Results 79 3.1 Overview of the results . 79 3.2 Spoken fricatives . 79 3.2.1 Aerodynamic results . 79 3.2.2 Acoustic results . 84 3.3 Mechanical fricatives . 90 3.3.1 Aerodynamic results . 90 3.3.2 Acoustic results . 92 Ensemble-averaged data for mechanical fricatives . 97 4 Discussion and Conclusions 100 4.1 Summary of the results . 100 4.2 Nasal harmony . 104 4.3 Velopharyngeal dysfunction . 105 4.4 Voiceless nasals . 106 4.5 Sibilants and non-sibilants . 108 4.6 Universals, rarities, and the expanding IPA . 109 4.6.1 An infinite phonetic alphabet? . 110 4.6.2 The IPA as a Cartesian coordinate system . 113 4.6.3 Nasalized fricatives: Shaded or empty cell? . 114 iv List of Figures 1.1 Tube model of the vocal tract . 1 1.2 Relationship of pressure behind a constriction in a tube and volume velocity 7 1.3 FFT of a uniformly-distributed random process . 9 1.4 FFT of a voiceless alveolar fricative . 10 2.1 Audio, oral flow, and nasal flow during ˜Af˜A (Hindi) . 54 2.2 FFT of an alveolar [s] produced with speaker wearing Scicon OM-2 (oral.