Segmental level analysis of laryngeal function in persons with motor speech disorders.

Laryngeal behavior for segmental function is often disturbed in motor speech disorders. Loss of voicing contrasts has been shown to significantly contribute to speech intelligibility deficits. The present study was designed to examine two commonly erred laryngeal contrasts, the word-initial voiced-voiceless and glottal-null contrasts using acoustic analysis techniques. Acoustic measures were compared to expectations for the contrast based on data in the literature as well as listeners' perception of the token. Findings indicate a mismatch between acoustic data and both expectations for the contrasts and listener perception. There is some indication that changes in laryngeal segmental function are related to aging in general and may be exaggerated in persons with motor speech disorders.

The relationship between perception and acoustics for a high-low vowel contrast produced by speakers with dysarthria.

This study was designed to explore the relationship between perception of a high-low vowel contrast and its acoustic correlates in tokens produced by persons with motor speech disorders. An intelligibility test designed by Kent, Weismer, Kent, and Rosenbek (1989a) groups target and error words in minimal-pair contrasts. This format allows for construction of phonetic error profiles based on listener responses, thus allowing for a direct comparison of the acoustic characteristics of vowels perceived as the intended target with those heard as something other than the target. The high-low vowel contrast was found to be a consistent error across clinical groups and therefore was selected for acoustic analysis. The contrast was expected to have well-defined acoustic measures or correlates, derived from the literature, that directly relate to a listeners' responses for that token. These measures include the difference between the second and first formant frequency (F2-F1), the difference between F1 and the fundamental frequency (FO), and vowel duration. Results showed that the acoustic characteristics of tongue-height errors were not clearly differentiated from the acoustic characteristics of targets. Rather, the acoustic characteristics of errors often looked like noisy (nonprototypical) versions of the targets. Results are discussed in terms of the test from which the errors were derived and within the framework of speech perception theory.

Perceptuo-acoustic assessment of prosodic impairment in dysarthria.

Dysprosody was studied in four groups of male subjects: subjects with amyotrophic lateral sclerosis (ALS) and mild intelligibility impairment, subjects with ALS and a more severe intelligibility loss, subjects with cerebellar disease, and neurologically normal controls. Dysprosody was assessed with perceptual ratings and acoustic measures pertaining to the regulation of duration, ƒ(0), and intensity within tone units of conversational samples. Intelligibility reduction and prosodic disturbance were not necessarily equally impaired in all subjects, and it is concluded that these are complementary indices of severity of dysarthria. Compared to the neurologically normal control group, the clinical groups tended to decrease the overall duration of tone units, produce fewer words in a tone unit, and use smaller variations in ƒ(0). Recommendations are offered for the assessement of.

Influences of pellet markers on speech production behavior: acoustical and perceptual measures.

Peri- and intraoral devices are often used to obtain measurements concerning articulator motions and placements. Surprisingly, there are few formal evaluations of the potential influence of these devices on speech production behavior. In particular, the potential effects of lingual pellets or coils used in x-ray or electromagnetic studies of tongue motion have never been evaluated formally, even though a large x-ray database exists and electromagnetic systems are commercially available. The x-ray microbeam database [Westbury, J. "X-ray Microbeam Speech Production Database User's Handbook, version 1" (1994)] includes several utterances produced with pellets-off and -on, which allowed us to evaluate effects of pellets for the utterance, She had your dark suit in greasy wash water all year, using acoustic and perceptual measures. Overall, there were no acoustic or perceptual measures that showed consistent effects of pellets across speakers, but certain effects were consistent either within a given speaker or in direction across a subgroup of the speakers. The results are discussed in terms of the general goodness of the assumption that point parameterization of lingual motion does not interfere with normal articulatory behaviors. A brief screening procedure is suggested to protect articulatory kinematic experiments from those individuals who may show consistent effects of having devices placed on perioral structures.

Evaluation of a reiterant force-impulse task in the tongue.

In the current study characteristics of a lingual force-impulse task were examined. In the task, neurologically normal adults were required to produce sequences of lingual force impulses that were modeled on sequences of syllables produced as reiterant speech. The goal of data analysis was to (a) compare the timing of the reiterant force sequences to the timing of reiterant speech sequences, (b) compare the force magnitudes to expected force variations associated with linguistic stress in the reiterant speech sequences, and (c) compare the reiterant force magnitudes to maximum lingual forces. Results indicated that reiterant force timing is typically slower than reiterant speech timing, that reiterant force magnitudes do not vary systematically as a function of stress variations in the reiterant speech utterances, and that reiterant force magnitudes are typically only a fraction of maximum lingual forces. Results are discussed in terms of the relationship between orofacial, nonspeech motor performance and speech production performance.