Understanding Synthetic Speech and Language Processing of Students With and Without a Reading Disability
Todd Richard Cunningham, University of Toronto , Canada
University of Toronto . Awarded
To help circumvent reading disability (RD) decoding difficulty, Text-To-Speech (TTS) software can be used to present written language audibly. Although TTS software is currently being used to help RD students, there is a lack of empirically supported literature to inform developers and users of TTS software on best practices. This dissertation investigated two methods to determine whether they increase the effectiveness of TTS for RD and typically-developing students. The first method compared low and high quality TTS voices in regards to understanding. TTS voice quality was identified by having 40 university students listen to and rate the quality of 10 commonly used TTS voices and 2 human voices. Three voices were chosen for the subsequent study based on the ratings; one low quality TTS, one high quality TTS, and one natural voice (Microsoft Mary, AT&T Crystal, and Susan, respectively). Understanding was assessed with tests of intelligibility and comprehensibility. Forty-five grade 6 to 8 students who were identified as having a RD were compared to same-age typically-developing peers. Results showed high quality TTS and natural voice were more intelligible than the low quality TTS voice, and high quality TTS voice resulted in higher comprehensibility scores than low quality TTS and natural voice.
The second method investigated whether it is possible to increase a student's comprehension when using TTS by modifying the presentation style of the TTS voice. The presentation style was manipulated in two ways: varying the speed at which the TTS presented the materials (120, 150, 180 words per minute) and the presence of pauses varied (no pauses inserted, random pauses inserted, or 500 millisecond pauses at the end of noun phrases). Due to a floor effect on the comprehension of the texts the expected results were not obtained. A follow up analysis compared the participants' prosodic sensitivity skills based on whether they had a specific language impairment, (SLI) a reading impairment (RI), or were typically-developing. Results suggested that SLI has significantly less auditory working memory then RI impacting their auditory processing. Recommendations for future research and the use of TTS based on different learning profiles are provided.
Cunningham, T.R. Understanding Synthetic Speech and Language Processing of Students With and Without a Reading Disability. Ph.D. thesis, University of Toronto.
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