Date of Award
Spring 5-2025
Document Type
Honors Thesis
Department/Major
Arts and Sciences
First Advisor
Dr. Elizabeth K. Hanson
Second Advisor
Shelly Grinde
Third Advisor
Dr. Taylor Bosch
Keywords
Primary Progressive Apraxia of Speech, intelligibility, naturalness, workload, natural speech, synthesized speech
Abstract
Primary Progressive Apraxia of Speech (PPAoS) is a neurodegenerative disease characterized by deficits in motor planning abilities for speech. Individuals with PPAoS experience phonetic and prosodic differences in their speech, affecting intelligibility, naturalness, speaking rate, and fluency. When a person’s speech is disordered, communication breakdowns may occur. Some individuals with disordered speech choose to use a text-to-speech program that synthesizes speech to improve communication. The differences between natural speech and synthesized speech have seldom been studied in relation to PPAoS.
This study focused on the differences in intelligibility, naturalness, and listener workload between natural and synthesized speech. To gather information about the three separate variables, participants were recruited from the student population on a university campus. Twenty-five students participated in a listening activity where they were randomly assigned to listen to recordings of either natural or synthesized speech. Participants transcribed the phrases in English as they heard the recordings. Participants also rated the naturalness of the speech. Finally, participants filled out a questionnaire to determine workload exerted for the task.
Intelligibility scores were higher for the synthesized speech. Naturalness scores were not significantly different between the two groups. Listener workload scores were lower for participants who listened to synthesized speech.
The findings demonstrated the usefulness of synthesized speech with a speech-generating device as the increased intelligibility and decreased listener workload suggest it is more effective than disordered natural speech. Therefore, the results provided important information about improving communication by using a speech-generating device in place of disordered speech.
Recommended Citation
Tegethoff, Kaitlyn S., "A Comparison of Natural and Synthesized Speech in a Case of Primary Progressive Apraxia of Speech" (2025). Honors Thesis. 380.
https://red.library.usd.edu/honors-thesis/380