University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Public Access Theses and Dissertations from Education and Human Sciences, College of the College of Education and Human Sciences (CEHS) July 2010 The Perception of Natural, Cell Phone, and Computer-Synthesized Speech During The Performance Of Simultaneous Visual-Motor Tasks Nirmal Kumar Srinivasan University of Nebraska at Lincoln, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/cehsdiss Part of the Special Education and Teaching Commons Srinivasan, Nirmal Kumar, "The Perception of Natural, Cell Phone, and Computer-Synthesized Speech During The Performance Of Simultaneous Visual-Motor Tasks" (2010). Public Access Theses and Dissertations from the College of Education and Human Sciences. 80. https://digitalcommons.unl.edu/cehsdiss/80 This Article is brought to you for free and open access by the Education and Human Sciences, College of (CEHS) at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Public Access Theses and Dissertations from the College of Education and Human Sciences by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. THE PERCEPTION OF NATURAL, CELL PHONE, AND COMPUTER- SYNTHESIZED SPEECH DURING THE PERFORMANCE OF SIMULTANEOUS VISUAL-MOTOR TASKS by Nirmal Kumar Srinivasan A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the of Degree Doctor of Philosophy Major: Intradepartmental Area of Human Sciences (Communication Disorders) Under the Supervision of Professor Thomas. D. Carrell Lincoln, Nebraska August, 2010 THE PERCEPTION OF NATURAL, CELL PHONE, AND COMPUTER- SYNTHESIZED SPEECH DURING THE PERFORMANCE OF SIMULTANEOUS VISUAL-MOTOR TASKS Nirmal Kumar Srinivasan , Ph.D. University of Nebraska, 2010 Advisor: Thomas. D. Carrell This study investigated the influence of top-down and bottom-up information on speech perception in complex listening environments. Specifically, the effects of listening to different types of processed speech were examined on intelligibility and on simultaneous visual-motor performance. The goal was to extend the generalizability of results in speech perception to environments outside of the laboratory. The effect of bottom-up information was evaluated with natural, cell phone and synthetic speech. The effect of simultan eous tasks was evaluated with concurrent visual-motor and memory tasks. Earlier works on the perception of speech during simultaneous visual-motor tasks have shown inconsistent results (Choi, 2004; Strayer & J ohnston, 2001). In the present experiments, two dual-task paradigms were constructed in order to mimic non-laboratory listening environments. In the first two experiments, an auditory word repetition task was the primary task and a visual-motor task was the secondary task. Participants were presented with different kinds of speech in a background of multi-speaker babble and were asked to repeat the last word of every sentence while doing the simultaneous tracking task. Word accuracy and visual-motor task performance were measured. Taken together, the results of Experiments 1 and 2 showed that the intelligibility of natural speech was better than synthetic speech and that synthetic speech was better perceived than cell phone speech. The visual- motor methodology was found to demonstrate independent and supplemental information and provided a better understanding of the entire speech perception process. Experiment 3 was conducted to determine whether the automaticity of the tasks (Schneider & Shiffrin, 1977) helped to explain the results of the first two experiments. It was found that cell phone speech allowed better simultaneou s pursuit rotor performance only at low intelligibility levels when participants ignored the listening task. Also, simultaneous task performance improved dramatically for natural speech when intelligibility was good. Overall, it could be concluded that knowledge of intelligibility alone is insufficient to characterize processing of different speech sources. Additional measures such as attentional demands and performance of simultaneous tasks were also important in characterizing the perception of different kinds of speech in complex listening environments. ACKNOWLEDGEMENTS My doctoral training has been an extremely enriching learning experience and I would like to take this opportunity to thank the numerous people who have contributed and helped me throughout this journey. My greatest gratitude to them may not be enough to reflect their contributions to this dissertation and my academic and professional growth. First and foremost, I would like to acknowledge my mentor, Dr. Thomas Carrell, for providing an opportunity to work under h is guidance. He has been a constant source of support throughout my MS and PhD study. He is a great mentor and a very active person who cares greatly about the success of his students. His valuable support, guidance, supervision, and motivation during my PhD program influenced and shaped this dissertation work. His scientific expertise and acumen has and will always be a constant source of inspiration for me. He has provided me with complete independence to learn from my mistakes which has helped me to grow as a better researcher. His honor, patience, work ethics, and integrity will serve as the base line performance I will strive for as I continue to grow in my research career. My greatly indebted to Dr. Jordan Green, Dr. Newell Decker, and Dr. Cal Garbin for consenting to serve as my dissertation committee members. I appreciate their feedback, suggestions, and guidance during this research through their technical knowledge and expertise. I extend my special thanks iv to Dr. Jordan Green and Dr. Newell Decker , members of my dissertation reading committee, in carefully evaluating this dissertation and their feedback for improving this dissertation. I am indebted to Dr. J ordan Green for introducing me to the world of Speech Science; his dedication to the field ignited me to investigate beyond the surroundings and look at the big picture. My heartfelt acknowledgements to Barkley Memorial Center and especially to Dr. John Bernthal for their continuous support throughout my graduate school. My special thanks to the past and present doctoral students in Barkley Memorial Center: Iggy, Antje, Sangsook, Nori, James, Wendy, Dave, Kelly, Sarah, Jill, Katy, Anusha, Shari, Chris, Kelly, and Trisha. A special thanks to my long time room -mate and a good friend, Vettrivel, for his inputs during experimental design, data collection, and data analysis. I would also like to thank my numerous other friends at Lincoln and other parts of the world for their continuous support and encouragement during this dissertation. I have gained benefit from many other teachers between then and now, and I feel (in most cases belatedly) grateful to them all. At the risk of unfair omissions resulting from poor memory, I would like to mark my gratitude to Mary Evelene, Kokila, Sharadha, J ikki, Balasubramanian, Xavier, Natarajan, Rex Johnson, Parvat Kumar Raut, Senthil Kumar, and Harshvardhan Gupta. v This accomplishment would never have been possible without the inspiration of my parents, Srinivasan and Mythili. They taught me work ethics, patience, perseverance, and principles and never had any doubts in me during the course of this entire dissertation. You are the best in this world. I would also like to thank my other family members: Sairam, Kamesh, Prashanthi, Arthi, Uma, Arun, Adithya, and Chirag for their love and support. Last, but not the least, I would like to thank Dharini for her continuous support and love throughout the dissertation process. Without her help, finishing up this dissertation would have been close to impossible. vi TABLE OF CONTENTS List of Tables Figure Captions Appendices Introduction ..................................................................................................................... 1 Literature Review ......................................................................................................... 14 Theories of Speech Perception ............................................................................... 16 Bottom-up Processes in Speech Perception. ................................................... 17 Top-down Processes in Speech Perception...................................................... 18 Theories of Speech Perception. .......................................................................... 20 Limitations of current theories of speech perception. .................................. 25 Description of Signals to be Investigated ............................................................ 28 Telephony. .............................................................................................................. 29 Source-filter model of speech production. ....................................................... 34 Analysis-by-Synthesis. ........................................................................................ 37 Channel ....................................................................................................................... 39 Effect of noise. ....................................................................................................... 40 Effect of reverberation. ........................................................................................ 42