Assessment, Control and Modification of Oral-nasal Balance in Speech by Gillian Lorna de Boer A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Rehabilitation Sciences Institute – Speech-Language Pathology University of Toronto © Copyright by Gillian Lorna de Boer 2018 i Assessment, Control and Modification of Oral-nasal Balance in Speech Gillian Lorna de Boer Doctor of Philosophy Rehabilitation Sciences Institute – Speech-Language Pathology University of Toronto 2018 Abstract In normal speech, oral sounds resonate in the oral cavity, and nasal sounds such as m, and n resonate in the nasal cavities. The velopharyngeal sphincter closes for oral sounds and opens for nasal sounds. The studies presented in this thesis sought to advance the assessment, control and modification of oral-nasal balance in speech. While the research was carried out in normal speakers, the intention was to create knowledge that will ultimately improve the assessment and behavioural treatment of speakers with oral-nasal balance disorders due to cleft palate. The first study (de Boer and Bressmann, 2016 a) was a retrospective analysis of normal speakers simulating different disorders of oral-nasal balance (hypernasality, hyponasality and mixed nasality). The recordings were analyzed acoustically using Long Term Averaged Spectra. The simulations produced distinctive spectra enabling the creation of formulas that predicted the oral- nasal balance well above chance level. The second study (de Boer & Bressmann, 2017) explored the role of auditory feedback in the regulation of oral-nasal balance in speech. In an altered auditory feedback paradigm, speakers of Canadian English compensated more for increased nasality than decreased nasality. This suggested that the speakers were less critical of a lack of nasality (hyponasality) than excess nasality (hypernasality). ii The third study (de Boer, Marino, Berti, Fabron, & Bressmann, 2016) investigated how voice focus affects oral-nasal balance in normal Brazilian speaking individuals. Participants read stimuli with their normal voice, a backward focus and a forward focus. The mean nasalance scores of the stimuli in the backward focus and normal speaking conditions were significantly lower than in the forward focus condition. The results confirmed that speaking focus influences oral-nasal balance in normal speakers, which could be useful for the development of new approaches of behavioural therapy. The research presented expands our understanding of oral-nasal balance control and lays the groundwork for new ways of clinically assessing and managing oral-nasal balance disorders. iii Acknowledgments Dr. Tim Bressmann has been a supervisor, mentor and friend. Always encouraging, he kept me on track, and rescued me from many intellectual rabbit holes. I continue to marvel at his curiosity which stretches across academia to global cuisine and candy. Throughout my Masters and Doctoral degree, Drs. Pascal van Lieshout and Gajanan (Kiran) Kulkarni served on my supervisory committee. Their questions and constructive criticisms helped to shape my graduate studies. I am especially grateful for the care and attention they dedicated to earlier versions of this thesis. I would like to acknowledge the Ontario Graduate Scholarship program for funding much of my doctoral degree. I am also grateful to Mitacs, whose Globalink award enabled me to travel to Brazil and work with leaders in my field, including Drs. Viviane Marino, Jeniffer Dutka and Maria-Ines Pegoraro-Krook. During that trip, I was spoiled by the hospitality of my hosts Dr. Larissa Berti and her family. They served many wonderful Sunday lunches and provided me with the ever encouraging pineapple metaphor (“It’s a lot of work, but worth it”). I will fondly remember coffees and lunches with Dr. Viviane Marino for years to come. I am also grateful to Dr. Eliana Fabron for her incredible kindness and generosity. My time in the lab was enriched by the friendships developed with fellow students and researchers, Dr. Larissa Berti, Amanda Ratner, Charlene Santoni, Elke Sapper, Monique Tardif and Gabriella Zuin. I am also grateful to a number of volunteers for their assistance with the second study: Sheetal Ramaprasad, Bianca Cohn, Yaxin Liu, Roubina Sarkissian, Marika Loy, iv and Karalina Lovkina. Though dedicated to other projects in the lab, the company of Joanna Hunt and Alissa Varlamova was also very much appreciated. Outside the lab I would like to thank Diane’s Tuesday/Thursday Triple Blast class and Viola’s Dance Like You Mean It studio for keeping me moving and sane. Finally, I would like to thank Michael, my partner, my rock, who’s had my back since the day we met. v Table of Contents Acknowledgments.......................................................................................................................... iv List of Tables .................................................................................................................................. x List of Figures ................................................................................................................................ xi List of Appendices ........................................................................................................................ xii Chapter 1 - General introduction .................................................................................................... 1 1.0 Speech production ................................................................................................................. 1 1.0.1 Resonance vs. oral-nasal balance ................................................................................... 2 1.1 Nasals and nasalized vowels ................................................................................................. 3 1.1.1 Acoustic characteristics of nasals and nasalized vowels ................................................ 4 1.1.2 Velopharyngeal sphincter function ................................................................................. 4 1.1.3 Velopharyngeal musculature .......................................................................................... 5 1.1.4 Velopharyngeal innervation and control ........................................................................ 8 1.1.5 Velopharyngeal closure ................................................................................................ 12 1.1.6 The nose and nasal cavities .......................................................................................... 14 1.2 Disordered oral-nasal balance ............................................................................................. 14 1.3 Assessment of disorders of oral-nasal balance .................................................................... 17 1.3.1 Perceptual ..................................................................................................................... 17 1.3.2 Instrumental assessment: Visual assessment of velopharyngeal function .................... 19 1.3.3 Instrumental assessment: Acoustic measurement of oral-nasal balance ...................... 20 1.4 Treatment of oral-nasal balance disorders .......................................................................... 23 1.4.1 Surgery.......................................................................................................................... 23 1.4.2 Prosthetics ..................................................................................................................... 24 1.4.3 Speech therapy .............................................................................................................. 24 1.5 Thesis objectives ................................................................................................................. 30 Chapter 2 - Application of linear discriminant analysis to the Long Term Averaged Spectra of simulated disorders of oral-nasal balance ..................................................................................... 33 2.0 Abstract ............................................................................................................................... 34 2.2 Methods ............................................................................................................................... 41 2.2.1 Participants ................................................................................................................... 41 2.2.2 Participant Training ...................................................................................................... 42 vi 2.2.3 Stimuli .......................................................................................................................... 42 2.2.4 Recording Procedures ................................................................................................... 43 2.2.5 Simulation Verification ................................................................................................ 43 2.2.6 Acoustic Analysis ......................................................................................................... 43 2.2.7 Statistical Analysis ....................................................................................................... 44 2.3 Results ................................................................................................................................. 44 2.3.1 Repeated Measures ANOVA .......................................................................................