Kate Bunton

Speech versus Nonspeech: Different Tasks, Different Neural Organization

This article reviews the extant studies of the relation of oromotor nonspeech activities to speech production. The relevancy of nonspeech oral motor behaviors to speech motor performance in assessment and treatment is challenged on several grounds. First, contemporary motor theory suggests that movement control is task specific. In other words, it is tied to the unique goals, sources of information, and characteristics of varying motor acts. Documented differences in movement characteristics for speech production versus nonspeech oral motor tasks support this claim. Second, advantages of training nonspeech oral motor tasks versus training speech production are not supported by current principles of motor learning and neural plasticity. Empirical data supports experience-specific training. Finally, functional imaging studies document differences in activation patterns for speech compared with nonspeech oral motor tasks in neurologically healthy individuals.

Perceptual effects of a flattened fundamental frequency at the sentence level under different listening conditions.

UNLABELLED The purpose of this series of experiments was to examine the effect of a flattened fundamental frequency (F0) contour on the intelligibility of sentence length material in different listening environments. Eight speakers of different genders and ages produced sentences from the Speech Perception in Noise Test (SPIN). Each utterance was subjected to a resynthesis technique that allowed flattening of the fundamental frequency while maintaining the timing and spectral characteristics of the utterances. To avoid learning effects two groups of listeners were chosen to complete word transcription and interval scaling tasks of the unmodified and flattened F0 utterances under different listening conditions (competing white noise or multi-speaker babble) to obtain measures of speech intelligibility. Results were that a flattened fundamental frequency contour negatively influences speech intelligibility regardless of the nature of the competing background noise. LEARNING OUTCOMES (1) To appreciate the role fundamental frequency variation plays in speech intelligibility. (2) To understand the importance of considering environmental noise in clinical speech intelligibility testing.

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, ƒ0, 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 ƒ0. Recommendations are offered for the assessement of

An evaluation of articulatory working space area in vowel production of adults with Down syndrome

Many adolescents and adults with Down syndrome have reduced speech intelligibility. Reasons for this reduction may relate to differences in anatomy and physiology, both of which are important for creating an intelligible speech signal. The purpose of this study was to document acoustic vowel space and articulatory working space for two adult speakers with Down syndrome who had reduced speech intelligibility (mean = 56% based on single words). Articulatory data for the tongue were collected using a real-time flesh-point tracking method (i.e. X-ray microbeam). Results show smaller F1–F2 acoustic vowel space area for both speakers with Down syndrome compared with the control speakers. Reduced articulatory working space area and slower movement speed were also found for three of the four tongue points analysed. Although generalizations are limited by the small number of participants, findings warrant further investigation of the underlying articulatory characteristics of speech production for individuals with Down syndrome.

Supracricoid partial laryngectomy: swallowing, voice, and speech outcomes.

Objectives: The purpose of the study was to describe the swallowing and vocal function of patients after supracricoid partial laryngectomy (SCPL) as they changed over the first postoperative year. Methods: Ten patients with laryngeal carcinoma underwent SCPL at Johns Hopkins Hospital between August 2003 and May 2005. Clinical and videofluoroscopic swallowing examinations and perceptual, acoustic, aerodynamic, and videostroboscopic voice evaluations were completed before operation and at 3 weeks (swallowing only) and 2 (voice only), 6, and 12 months after operation. Results: The mean time to gastrostomy tube removal was 82 days. The patients tolerated an increased variety of foods over the first postoperative year. All patients initially used therapeutic strategies to swallow safely, and some still required them at 1 postoperative year. Over the year, the perceptual ratings of voice quality improved significantly. There were no consistent changes in acoustic or aerodynamic measures. The number of patients who used multiple vibratory sources to phonate increased over the year. Conclusions: The patients tolerated regular diets, yet continued to exhibit silent aspiration and a variety of decompensations. Their voices were breathy, rough, and strained. Their voice quality ratings improved over the year. Group changes were not captured, and it appears that the changes in speech and voice 2 months after surgery were subtle.

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.

Fundamental frequency as a perceptual cue for vowel identification in speakers with parkinson's disease

This study investigates the importance of fundamental frequency (F0) as a perceptual cue for identification of vowel targets produced by speakers with Parkinson’s disease (PD). It has been suggested in the literature that F0 is a redundant cue for vowel identification in highly intelligible speech. For speakers with dysarthria who are having difficulty with segmental and suprasegmental aspects of production which result in ambiguous or conflicting cues in the acoustic signal, F0 may have increased perceptual importance for accurate identification of vowel targets. In the present study, F0 contours for single-word targets produced in sentence level material by 20 speakers with PD and 20 control speakers were synthetically modified in several different ways (i.e., flattened and enhanced). Listener identification of vowel targets across the F0 conditions was recorded. The accuracy of vowel identification for the control group was not affected by the flattening of the F0 contour. For the speakers with PD, however, modification of the F0 contour (flattening or enhancing) affected the accuracy with which listeners identified certain vowels. Differences in vowel identification were found primarily for the front vowels /I, Ε, æ/ along a high-low continuum.

A Simple Technique for Determining Velopharyngeal Status during Speech Production

Clinical evaluation of velopharyngeal function relies heavily on auditory perceptual judgments that can be supported by instrumental examination of the velopharyngeal valve. Many of the current instrumental techniques are difficult to interpret, expensive, and/or unavailable to clinicians. Proposed in this report is a minimally invasive and inexpensive approach to evaluating velopharyngeal function that has been used successfully in our laboratory for several potentially difficult-to-test clients. The technique is an aeromechanical approach that involves the sensing of nasal ram pressure (N-RamP), a local pressure sensed at the anterior nares, using a two-pronged nasal cannula. By monitoring the N-RamP signal, it is possible to determine the status of the velopharyngeal port (open or closed) during speech production. Four case examples are presented to support its clinical value.

Identification of synthetic vowels based on a time-varying model of the vocal tract area function

The purpose of this study was to conduct an identification experiment with synthetic vowels based on the same sets of speaker-dependent area functions as in Bunton and Story [(2009) J. Acoust. Soc. Am. 125, 19-22], but with additional time-varying characteristics that are more representative of natural speech. The results indicated that vowels synthesized using an area function model that allows for time variation of the vocal tract shape and includes natural vowel durations were more accurately identified for 7 of 11 English vowels than those based on static area functions.

The Relation of Nasality and Nasalance to Nasal Port Area Based on a Computational Model

Objective The purpose of this study was to examine the relation of perceptual ratings of nasality by experienced listeners, measures of nasalance, and the size of the nasal port opening for three simulated English corner vowels, /i/, /u/, and /a/. Design Samples were generated using a computational model that allowed for exact control of nasal port size and a direct measure of nasalance. Perceptual ratings were obtained using a paired-stimulus presentation. Participants Five experienced listeners. Main Outcome Measures Measures of nasalance and perceptual nasality ratings. Results Differences in nasalance and perceptual ratings of nasality were noted among the three vowels, with values being greater for the high vowels /i/ and /u/ compared to the low vowel Id. Listeners detected nasality for the high and low vowels simulated with nasal port areas of 0.01 and 0.15 cm2, respectively. Correlations between ratings of nasality and nasalance were high for all three vowels. Conclusions Results of the present study show a high correlation between ratings of nasality and measures of nasalance for nasal port areas ranging from 0 to 0.5 cm2. The correlations were based on sustained vowel samples. The restricted speech sample limits generalization of the findings to clinical data; however, the results are a demonstration of the usefulness of modeling to understand the perceptual phenomena of nasality.