An Acoustic, Aerodynamic and Perceptual Investigation of Word-Initial Denasalization in Korean
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An acoustic, aerodynamic and perceptual investigation of word-initial denasalization in Korean Young Shin Kim A dissertation submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy of University College London. Department of Speech, Hearing and Phonetic Sciences UCL 2011 2 I, Young Shin Kim, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis. Young Shin Kim 김영신 (金英信) 3 Abstract Korean nasals /m/ and /n/ are generally considered by Korean phoneticians to be hardly different from the corresponding English sounds, but those in word-initial position are often perceived as plosives by native speakers of English. This had been noted by only a few previous observers, and investigated on a very limited scale. In this study, various experimental methods were employed in systematic analyses of the production and acoustic form of word-initial /m/ and /n/ from fluent connected speech collected from a relatively large number of informants, and corresponding perception tests were conducted with groups of Korean and English listeners. Auditory and spectrographic analyses confirmed that the segments were commonly “denasalized”. They display characteristics widely different from those of sonorant nasals, lacking the nasal formants commonly seen in spectrograms; in most cases they were more similar to voiced plosives, many tokens even showing plosive- like release bursts. Spectral analyses confirmed that denasalized nasals are significantly different from sonorant nasals throughout the whole frequency range but remain somewhat different from voiced plosives in the low and high frequency regions. Aerodynamic and accelerometer studies, which examined the consonants in CV combinations, indicated that the denasalized sounds are evidently produced with a pattern of velopharyngeal control which is different from those of sonorant nasals or of plosives. Perception tests showed overwhelmingly that the word-initial denasalized sounds are categorized as nasals by Korean listeners but as plosives by English listeners. When real voiced plosive tokens from another context are artificially moved to word-initial position, Koreans perceive these too as nasals, while English listeners’ responses are not sensitive to the context. The study shows that denasalization needs to be acknowledged as a major regular feature of spoken Korean, even though it has been largely ignored up to now. Directions for further research are outlined. 4 Acknowledgements I would like to express my gratitude to those who have helped me during my time at UCL. First and foremost I would like to thank my supervisor, Michael Ashby, for his guidance, support and encouragement. I would also like to thank Steve Nevard and Dave Cushing for their expert help and discussion in the lab, and Gaston Hilkhuysen for his assistance with statistical issues. I am also grateful to my fellow students and colleagues at UCL, Jeong Sug Kyong, Kayoko Yanagisawa, Melanie Pinet, Chierh Cheng, Sophie Gates and Katharine Mair for their support and discussion, and especially, Dong Jin Shin who provided great help with recruiting subjects. I am immensely grateful to my parents, Kwang Il Kim and Kyeong Ok Lim, and also to my sister and brother, Young Joo and Dong Ho, for their love and support. To the many people who played a part, whether named here or not, thank you. 5 Contents 1 Introduction ..................................................................................................... 14 Pilot studies .......................................................................................................... 15 Previous studies .................................................................................................... 16 The current thesis ................................................................................................. 17 Research questions and hypotheses ...................................................................... 18 2 Review of Literature ......................................................................................... 20 Part One. Phonetics of Korean ................................................................................... 20 2.1 Consonants …. ..................................................................................................... 21 2.2 Vowels ……… ..................................................................................................... 22 2.3 Allophonic rules in Korean .................................................................................. 23 Part Two. Phonology of Korean ................................................................................. 24 2.4 Syllable and syllabification .................................................................................. 24 2.5 Phonological environments for Korean nasals ..................................................... 26 2.6 Stress in Korean ………………………………………………………………..26 2.7 Phonotactic constraints of Korean ........................................................................ 29 Part Three. Nasality ........................................................................................................ 31 2.8 Nasality and the Velum ........................................................................................ 31 2.9 Nasals and Nasalized Consonants ........................................................................ 34 2.10 The Velum and Prosody ....................................................................................... 36 2.11 Acoustics of Nasals .............................................................................................. 36 2.12 Aerodynamics of Nasals ....................................................................................... 38 2.13 Denasalization ...................................................................................................... 42 6 3 Auditory and acoustic characteristics of denasalized nasals in Korean ................ 48 3.1 Introduction .......................................................................................................... 48 3.2 Method.................................................................................................................. 50 3.2.1 Speakers ..................................................................................................... 50 3.2.2 Recording materials ................................................................................... 51 3.2.3 Recording ................................................................................................... 51 3.2.4 Annotation .................................................................................................. 51 3.2.5 Filtering ...................................................................................................... 53 3.3 Results 1: Auditory analyses ................................................................................ 54 3.4 Results 2: 16-channel filterbank analyses ............................................................ 61 3.5 Discussion ............................................................................................................ 67 3.6 Conclusion ............................................................................................................ 68 4 Aerodynamic characteristics of denasalized nasals in Korean ............................. 70 4.1 Introduction .......................................................................................................... 70 4.2 Method.................................................................................................................. 72 4.2.1 Ethical approval ......................................................................................... 72 4.2.2 Speakers ……. ........................................................................................... 73 4.2.3 Recording materials ................................................................................... 74 4.2.4 The Masks …. ............................................................................................ 74 4.2.5 The Measurement System with Transducers ............................................. 75 4.2.6 Annotation ….. ........................................................................................... 76 4.2.7 Calibration of flow rates............................................................................. 77 4.2.8 Measurement of the flows .......................................................................... 78 4.3 Results 1: Nasal flow ............................................................................................ 83 4.4 Results 2: Denasalization and prosodic domains ................................................. 91 4.5 Discussion 1: Denasalized and nasal segments .................................................... 94 4.6 Discussion 2: Denasalization and prosodic hierarchy .......................................... 98 7 5 An accelerometer study on denasalization in Korean ....................................... 101 5.1 Introduction ........................................................................................................ 101 5.2 Method................................................................................................................ 102 5.2.1 Speakers ……. ......................................................................................... 102 5.2.2