Nancy Pearl Solomon

Recording single motor unit activity of human nasal muscles with surface electrodes: applications for respiration and speech

A method is presented for recording nasal single motor unit (SMU) potentials from the skin surface using a 3-pole branched bipolar electrode. Stable, high-quality recordings of single motor unit activity were obtained for up to 3 h. Branched electrode arrays were capable of locating an SMUs maximal voltage point within 5 mm. We examined nasal SMU discharge patterns in relation to respiration in 9 adult humans. The majority of SMUs which discharged during quiet breathing began firing late in expiration and ceased firing in mid-inspiration, other SMUs discharged only during expiration, and a few fired continually with frequency modulation during breath cycles. With increased ventilation, new SMUs were recruited, and previously active SMUs increased the frequency and duration of their discharge. We examined the discharge of 13 units (5 adults) which discharged during speech but were never active during quiet or moderately increased breathing. Some of these SMUs fired during production of nasal consonants, and others were active for articulations involving facial movements (bilabial stops, labio-dental fricatives, and vowels produced with lip movement). By providing information about motor neuron recruitment which cannot be obtained from gross EMG recordings, surface recording of unit potentials may be useful in studying the central nervous control of the nasal upper airway, face, and neck for respiration and speech.

Speech-related fatigue and fatigability in Parkinson’s disease

Abstract This study tested the assumption that speech is more susceptible to fatigue than normal in persons with dysarthria. After 1u2009h of speech-like exercises, participants with Parkinsons disease (PD) were expected to report increased perceptions of fatigue and demonstrate fatigability by producing less precise speech with corresponding acoustic changes compared to neurologically normal participants. Twelve adults with idiopathic PD and 13 neurologically normal adults produced sentences with multiple lingual targets before and after six 10-min blocks of fast syllable or word productions. Both groups reported increasing self-perceived fatigue over time, but trained listeners failed to detect systematic differences in articulatory precision or speech naturalness between sentences produced before and after speech-related exercises. Similarly, few systematic acoustic differences occurred. These findings do not support the hypothesis that dysarthric speakers are particularly susceptible to speech-related fatigue; instead, speech articulation generally appears to be resistant to fatigue induced by an hour of moderate functional exercises.

Spectral characteristics of speech with fixed jaw displacements

During speech, movements of the mandible and the tongue are interdependent. For some research purposes, the mandible may be constrained to ensure independent tongue motion. To examine specific spectral characteristics of speech with different jaw positions, ten normal adults produced sentences with multiple instances of /t/, /s/, /∫/, /i/, /ai/, and /ɔi/. Talkers produced stimuli with the jaw free to vary, and while gently biting on 2‐ and 5‐mm bite blocks unilaterally. Spectral moments of /s/ and /∫/ frication and /t/ bursts differed such that mean spectral energy decreased, and diffuseness and skewness increased with bite blocks. The specific size of the bite block had minimal effect on these results, which were most consistent for /s/. Formant analysis for the vocoids revealed lower F2 frequency in /i/ and at the end of the transition in /ai/ when bite blocks were used; F2 slope for diphthongs was not sensitive to differences in jaw position. Two potential explanations for these results involve the phy...

MacCAD, a new Macintosh‐based Hypercard program for central auditory diagnostics: Description and preliminary findings

Although most components of the classical auditory system lie between the periphery and association cortex, our information about auditory disorders is limited primarily to those extremes. This ignorance is due to the fact that until recently, appropriately sensitive methodologies, both in terms of test design as well as modes for noninvasive brain monitoring, have not been readily available in the clinic. MacCAD is an attempt to address the first of these issues; a companion paper will report on results combining MacCAD with noninvasive physiological testing [repeated evoked potentials (REPs)]. MacCAD brings features of basic‐research test design into the clinic, including: ease of use by both tester and client, monaural and dichotic modes for a variety of speech and nonspeech sounds, expansion capability for additional sounds, graduated difficulty for each sound set, client control of test pacing, automatic stimulus/response recording, trial‐by‐trial feedback, and analysis options including trial‐by‐tri...

Do clear-speech consonants always provide the best intelligibility for hearing-impaired listeners?

Hearing-aid amplification enhances speech intelligibility for many hearing-impaired (HI) listeners in quiet, but often provides no clear benefit in noise. Requesting that talkers use clear speech is one strategy to overcome these listening challenges. Paradoxically, one feature of clear speech is a shift to higher frequencies, which may move speech energy into a frequency range that is inaudible or has more distortion for certain HI listeners. Conversely, casual conversational speech may shift speech energy into a lower frequency range that is more audible or has less distortion. This study examined the intelligibility of 21 casually- and clearly-spoken American English coda consonants in nonsense syllables for 9 aided normal-hearing and 18 aided HI listeners. As expected, most clear-speech consonants yielded higher recognition scores. However, certain phonological processes common in casual speech, namely affrication and palatalization, generated significantly higher scores than their clear counterparts ...

The intelligibility of clear and conversational allophones of coda consonants

For many hearing-impaired (HI) listeners, hearing-aid amplification provides near-normal speech recognition in quiet. Nonetheless, many of these same listeners show large speech deficits, relative to normal-hearing (NH) listeners, that are not effectively addressed via amplification in noisy listening conditions. One compensating strategy HI listeners use is to ask talkers to speak clearly. However, as one of the features of clear speech is a shift to higher frequencies, HI listeners may not benefit as much as NH listeners if the new frequencies are outside their audible range. This study examined the intelligibility of conversationally- and clearly-spoken coda consonants in nonsense syllables. These free-variant allophones of 21 American English consonants were produced in three phonological environments: syllable (utterance) final; syllable final followed by schwa; and syllable final followed by palatal approximant and schwa. The stimuli were presented in broadband noise and in quiet to NH and HI listen...

The effect of lung volume on voice onset time

The mechanical linkage between the respiratory apparatus and the larynx may have consequences on the acoustic speech signal. For example, at high lung volumes, the diaphragm usually flattens and pulls the trachea and larynx caudally, exerting a force that abducts the vocal folds. This abductory force may delay the onset of vocal fold vibration that could be realized acoustically as a delay in voice onset time (VOT). To examine this possibility, five young men produced repetitions of a six‐syllable phrase containing two stressed /pi/ syllables from the total lung capacity to the residual volume. Lung volume was determined with magnetometry and VOT for each /pi/ syllable was measured from spectrograms. VOT generally was longer at higher lung volumes than at lower lung volumes in four of the five subjects. This finding supports our hypothesis that the mechanical linkage between the respiratory apparatus and larynx can influence voicing onset. Further, it suggests the need to take lung volume into account whe...