Speech naturalness ratings and perceptual correlates of highly natural and unnatural speech in hypokinetic dysarthria secondary to Parkinson's disease

Abstract

Despite the importance of speech naturalness to treatment outcomes, little research has been done on what constitutes speech naturalness and how to best maximize naturalness in relationship to other treatment goals like intelligibility. This study investigated the speech naturalness ratings of individuals with dysarthria and the associated perceptual correlates of highly natural and unnatural speech. Four speakers with hypokinetic dysarthria secondary to Parkinson’s disease were recorded and rated for naturalness by 69 students in Communication Disorders. Students were presented with 436 speech samples and asked to provide speech naturalness ratings on a 1-9 Likert scale. After rating speech samples, subjects listed perceptual cues associated with samples rated most and least natural and weighted each cue on a visual analog scale. The data on naturalness ratings showed that spontaneous speech was rated the least natural on average, while sentences from a short story were rated slightly more natural and individually read sentences were rated the most natural of all of the utterance types. Thirteen themes emerged from the perceptual cues collected. Of the thirteen themes, intelligibility was rated significantly more important than other cues in highly natural speech and intelligibility and articulation were rated significantly more important than other cues in highly unnatural speech.

The Effects of Modulating Fundamental Frequency and Speech Rate on the Intelligibility, Communication Efficiency, and Perceived Naturalness of Synthetic Speech

“…We hypothesized that sentence-level variations in f0 would reduce intelligibility while simultaneously enhancing naturalness (Klopfenstein, 2016). In line with this hypothesis, we found that synthetic speech produced at a fixed f0 level was more intelligible than when produced with sentence-level variation in f0.…”

“…Klopfenstein (2016) describes an ongoing struggle with balancing naturalness and intelligibility: Naturalness is linked to social communication, whereas intelligibility is often linked to efficacious communication (Anand & Stepp, 2015;Klopfenstein, 2016;Yorkston et al, 2010). An increase in one measure may be accompanied by a decrease in the other, and vice versa (Nusbaum, Francis, & Henly, 1997).…”

Levodopa-Based Changes on Vocalic Speech Movements during Prosodic Prominence Marking

“…This hypokinetic dysarthria affects all motoric subsystems of speech and leads to a reduced modulation of intensity and pitch, slower speech rate, imprecise articulation as well as an overall reduced articulation space [ 3 , 4 ]. Most studies on hypokinetic dysarthria are either based on perceptual intelligibility/ naturalness ratings [ 5 , 6 , 7 , 8 ] or acoustic speech analyses of standardized tasks, such as sustained vowel phonation, oral diadochokinesia (DDK) or a reading text [ 9 , 10 , 11 , 12 , 13 ].…”

“…In order to control for prosodic patterns that have been shown to influence the syllable internal coordination patterns, the study uses mini dialogues and avoids standardized tasks. Prosody is an important domain of speech production as it makes communication vivid, emotional, intelligible and more natural [ 5 , 19 ]. The ability to mark prominence (highlighting important words in a sentence) in the different domains of speech production (intensity, durational properties, pitch and vowel production) is tested in two conditions to examine the influence of motor performance on speech production further: without dopaminergic medication (bad motor performance) and with dopaminergic medication (improved motor performance due to levodopa intake).…”