The purpose of this study was to examine the relationship between scaled speech intelligibility and selected acoustic variables in persons with dysarthria. Control speakers and speakers with amyotrophic lateral sclerosis (ALS) and Parkinson’s disease (PD) produced sentences which were analyzed acoustically and perceptually. The acoustic variables included total utterance durations, segment durations, estimates of the acoustic vowel space, and slopes of formant transitions; the perceptual variables included scaled speech intelligibility and severity of speech involvement. Results indicated that the temporal variables typically differentiated the ALS group, but not the PD group, from the controls, and that vowel spaces were smaller for both neurogenic groups as compared to controls, but only significantly so for the ALS speakers. The relation of these acoustic measures to scaled speech intelligibility is shown to be complex, and the composite results are discussed in terms of sentence vs. single-word intelligibility estimates and their underlying acoustic bases.

The current study explored the acoustic and perceptual effects of speaking rate adjustments in persons with amyotrophic lateral sclerosis (ALS) and in neurologically normal individuals. Sentence utterances were obtained from the participants at two self-selected speaking rates: habitual and fast. Total utterance durations, segment durations, and vowel formant frequencies comprised the acoustic measures, whereas magnitude estimates of speech intelligibility and severity of speech involvement were the perceptual measures. Results showed that participants in both the neurologically normal and ALS groups were able to increase their speaking rate when asked to do so, but that the participants with ALS were significantly slower than the neurologically normal participants at both rates. Both groups of participants also showed compression of the acoustic vowel space with increased speaking rate, with the vowel spaces of participants with ALS generally being more compressed than the vowel spaces of neurologically normal participants, at either rate. Most importantly, the perceptual measures failed to show any effect of the speaking rate adjustment on scaled intelligibility or severity, for either group. These findings are discussed relative to the general issue of slow habitual speaking rates among many speakers with dysarthria, and possible explanations for the slowness. The lack of an effect of increased rate on the perception of the speech deficit among speakers with ALS argues against the idea that the habitually slow rates are a form of compensation to reduce the complexity of speech production.

The primary objective of the present study was to document tone production and intelligibility deficits in Mandarin-speaking persons with cerebral palsy (CP). Spastic, athetoid, and mixed types of CP were studied, along with a control group, to investigate the possibility of tone production and intelligibility deficits that were differentially affected by type of CP. Speakers produced a 78-word list that included contrasts for all four Mandarin tones. Intelligibility data were obtained for these words from 26 native speakers of Mandarin, and F0 contour analyses were implemented in CSpeech (Milenkovic) for a subset of the words. Mean tone intelligibility for speakers with CP was 73%, significantly different from the 91% value for control speakers. F0 contour analysis showed that speakers with CP maintained some contrast among the F0 contours for the four tones, but with less distinction than contrasts observed for control speakers. Discussion focuses on the role of tone in a model of the dysarthria associated with CP.

Retroflexed consonants are the most complex and difficult sounds for Mandarin speakers. The four retroflexed consonants in Mandarin are produced with the tip of the tongue retracted and curled up close to the positions of the hard palate. The purpose of this study was to investigate the acoustic characteristics of retroflexed consonants for normal speakers. The moment analysis and the noise duration of retroflexed and nonretroflexed fricatives and affricates were studied for 10 adult speakers. Moment analysis is a statistical approach for the power spectrum. The results showed that retroflexed consonants had lower mean noise frequencies (M1) than nonretroflexed consonants. The standard deviation of noise energy frequencies (M2) of retroflexed consonants was smaller than those of nonretroflexed consonants. Results will be discussed in terms of the linkage between acoustic data and tongue positions. The discriminate analysis by using moment and duration parameters to classify word-initial retro- flexed consonants was also reported.

Although sentence production is more common than single-word production in daily life, acoustic and intelligibility data from persons with neurogenic speech disorders is largely limited to single-word and target-word utterances. The purpose of the current study is to examine sentence productions of individuals with Parkinson’s disease (PD) and amyotrophic lateral sclerosis (ALS), and to compare them to data obtained from neurologically normal individuals. Each speaker produced multiple repetitions of a small set of sentences. Acoustic measures included overall sentence durations, segment durations, and vowel formant frequencies. Speech intelligibility of the sentences was measured using scaling techniques. For some subjects, previously obtained acoustic and intelligibility data for single words will be related to the findings for sentences. Results will be discussed descriptively as deviations from patterns observed in normal individuals, and in terms of associations between the acoustic and intelligibility data. [Work supported by NIDCD Award DC00319.]