The relation of velopharyngeal coupling area and vocal tract scaling to identification of stop-nasal cognates.

The purpose of this study was to determine whether the threshold of velopharyngeal (VP) coupling area at which listeners switch from identifying a consonant as a stop to a nasal in North American English was different for speech produced by a model based on an adult male, an adult female, and a 4-year-old child. V1CV2 stimuli were generated with a speech production model that encodes phonetic segments as relative acoustic targets imposed on an underlying vocal tract and laryngeal structure that can be scaled according to sex and age. Each V1CV2 was synthesized with a set of VP coupling functions whose maximum area ranged from 0 to 0.1 cm2. Results showed that scaling the vocal tract and vocal folds had essentially no effect on the VP coupling area at which listener identification shifted from stop to nasal. The range of coupling areas at which the crossover occurred was 0.037-0.049 cm2 for the male model, 0.040-0.055 cm2 for the female model, and 0.039-0.052 cm2 for the 4-year-old child model, and overall mean was 0.044 cm2. Calculations of band limited peak nasalance indicated that 85% peak nasalance during the consonant was well aligned with listener responses.

The relation of velopharyngeal coupling area to the identification of stop versus nasal consonants in North American English based on speech generated by acoustically driven vocal tract modulations.

The purpose of this study was to determine the threshold of velopharyngeal coupling area at which listeners switch from identifying a consonant as a stop to a nasal in North American English, based on V1CV2 stimuli generated with a speech production model that encodes phonetic segments as relative acoustic targets. Each V1CV2 was synthesized with a set of velopharyngeal coupling functions whose area ranged from 0 to 0.1 cm2. Results show that consonants were identified by listeners as a stop when the coupling area was less than 0.035-0.057 cm2, depending on place of articulation and final vowel. The smallest coupling area (0.035 cm2) at which the stop-to-nasal switch occurred was found for an alveolar consonant in the /ɑCi/ context, whereas the largest (0.057 cm2) was for a bilabial in /ɑCɑ/. For each stimulus, the balance of oral versus nasal acoustic energy was characterized by the peak nasalance during the consonant. Stimuli with peak nasalance below 40% were mostly identified by listeners as stops, whereas those above 40% were identified as nasals. This study was intended to be a precursor to further investigations using the same model but scaled to represent the developing speech production system of male and female talkers.

A model of speech production based on the acoustic relativity of the vocal tract.

A model is described in which the effects of articulatory movements to produce speech are generated by specifying relative acoustic events along a time axis. These events consist of directional changes of the vocal tract resonance frequencies that, when associated with a temporal event function, are transformed via acoustic sensitivity functions, into time-varying modulations of the vocal tract shape. Because the time course of the events may be considerably overlapped in time, coarticulatory effects are automatically generated. Production of sentence-level speech with the model is demonstrated with audio samples and vocal tract animations.

An age-dependent vocal tract model for males and females based on anatomic measurements.

The purpose of this study was to take a first step toward constructing a developmental and sex-specific version of a parametric vocal tract area function model representative of male and female vocal tracts ranging in age from infancy to 12 yrs, as well as adults. Anatomic measurements collected from a large imaging database of male and female children and adults provided the dataset from which length warping and cross-dimension scaling functions were derived, and applied to the adult-based vocal tract model to project it backward along an age continuum. The resulting model was assessed qualitatively by projecting hypothetical vocal tract shapes onto midsagittal images from the cohort of children, and quantitatively by comparison of formant frequencies produced by the model to those reported in the literature. An additional validation of modeled vocal tract shapes was made possible by comparison to cross-sectional area measurements obtained for children and adults using acoustic pharyngometry. This initial attempt to generate a sex-specific developmental vocal tract model paves a path to study the relation of vocal tract dimensions to documented prepubertal acoustic differences.

Vowel space density as an indicator of speech performance.

The purpose of this study was to develop a method for visualizing and assessing the characteristics of vowel production by measuring the local density of normalized F1 and F2 formant frequencies. The result is a three-dimensional plot called the vowel space density (VSD) and indicates the regions in the vowel space most heavily used by a talker during speech production. The area of a convex hull enclosing the vowel space at specific threshold density values was proposed as a means of quantifying the VSD.

An acoustically-driven vocal tract model for stop consonant production.

The purpose of this study was to further develop a multi-tier model of the vocal tract area function in which the modulations of shape to produce speech are generated by the product of a vowel substrate and a consonant superposition function. The new approach consists of specifying input parameters for a target consonant as a set of directional changes in the resonance frequencies of the vowel substrate. Using calculations of acoustic sensitivity functions, these "resonance deflection patterns" are transformed into time-varying deformations of the vocal tract shape without any direct specification of location or extent of the consonant constriction along the vocal tract. The configuration of the constrictions and expansions that are generated by this process were shown to be physiologically-realistic and produce speech sounds that are easily identifiable as the target consonants. This model is a useful enhancement for area function-based synthesis and can serve as a tool for understanding how the vocal tract is shaped by a talker during speech production.

Arizona Child Acoustic Database Repository.

OBJECTIVE: The goal of the Arizona Child Acoustic Database project was to obtain a large set of acoustic recordings, primarily vowels, collected from a cohort of children over a critical period of growth and development. METHOD: Data was recorded longitudinally from 63 children between the ages of 2;0 and 7;0 at 3-month intervals. The protocol included individual American English vowels and diphthongs, nonsense multi-vowel transitions, word level multi-vowel sequences (e.g., Hawaii), single-syllable words targeting each American English vowel, short sentences, and conversation. RESULTS: Acoustic files are available for download through the University of Arizona Library Repository for use in future research projects. CONCLUSION: Longitudinal recordings may be of interest because they allow tracking of acoustic characteristics produced by an individual child during a period of rapid growth and speech development.

Effects of nasal port area on perception of nasality and measures of nasalance based on computational modeling.

OBJECTIVE: This study examined the relation between nasal port area, nasalance, and perceptual ratings of nasality for three English corner vowels, /i/, /u/, and /a/. DESIGN: Samples were simulated using a computational model that allowed for exact control of nasal port size and direct measures of nasalance. Perceptual ratings were obtained using a paired stimulus presentation. PARTICIPANTS: Four experienced listeners. MAIN OUTCOME MEASURES: Nasalance and perceptual ratings of nasality. RESULTS: Findings show that perceptual ratings of nasality and nasalance increased for samples generated with nasal port areas up to and including 0.16 cm(2) but plateaued in samples generated with larger nasal port areas. No vowel differences were noted for perceptual ratings. CONCLUSIONS: This work extends previously published work by including nasal port areas representative of those reported in the literature for clinical populations. Continued work using samples with varied phonetic context and varying suprasegmental and temporal characteristics are needed.

Formant measurement in children's speech based on spectral filtering.

Children's speech presents a challenging problem for formant frequency measurement. In part, this is because high fundamental frequencies, typical of a children's speech production, generate widely spaced harmonic components that may undersample the spectral shape of the vocal tract transfer function. In addition, there is often a weakening of upper harmonic energy and a noise component due to glottal turbulence. The purpose of this study was to develop a formant measurement technique based on cepstral analysis that does not require modification of the cepstrum itself or transformation back to the spectral domain. Instead, a narrow-band spectrum is low-pass filtered with a cutoff point (i.e., cutoff "quefrency" in the terminology of cepstral analysis) to preserve only the spectral envelope. To test the method, speech representative of a 2-3 year-old child was simulated with an airway modulation model of speech production. The model, which includes physiologically-scaled vocal folds and vocal tract, generates sound output analogous to a microphone signal. The vocal tract resonance frequencies can be calculated independently of the output signal and thus provide test cases that allow for assessing the accuracy of the formant tracking algorithm. When applied to the simulated child-like speech, the spectral filtering approach was shown to provide a clear spectrographic representation of formant change over the time course of the signal, and facilitates tracking formant frequencies for further analysis.

Measures to Evaluate the Effects of DBS on Speech Production.

The purpose of this paper is to review and evaluate measures of speech production that could be used to document effects of Deep Brain Stimulation (DBS) on speech performance, especially in persons with Parkinson disease (PD). A small set of evaluative criteria for these measures is presented first, followed by consideration of several speech physiology and speech acoustic measures that have been studied frequently and reported on in the literature on normal speech production, and speech production affected by neuromotor disorders (dysarthria). Each measure is reviewed and evaluated against the evaluative criteria. Embedded within this review and evaluation is a presentation of new data relating speech motions to speech intelligibility measures in speakers with PD, amyotrophic lateral sclerosis (ALS), and control speakers (CS). These data are used to support the conclusion that at the present time the slope of second formant transitions (F2 slope), an acoustic measure, is well suited to make inferences to speech motion and to predict speech intelligibility. The use of other measures should not be ruled out, however, and we encourage further development of evaluative criteria for speech measures designed to probe the effects of DBS or any treatment with potential effects on speech production and communication skills.

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 /a/. Listeners detected nasality for the high and low vowels simulated with nasal port areas of 0.01 and 0.15 cm(2), 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 cm(2). 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.

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.

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.

Identification of voiced stop consonants produced by acoustically driven vocal tract modulations.

A recently developed speech production model, in which speech segments are specified by relative acoustic events called resonance deflection patterns, was used to generate speech signals that were presented to listeners in a perceptual test. The purpose was to determine the effect of variations of the magnitude and polarity of the third resonance deflection on identification of the consonant in a V1CV2 disyllable while the deflections of the first and second resonances were held constant. Result showed that listeners' identification changed from /d/ to /É¡/ when the polarity of the third resonance deflection switched from positive to negative.

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 video-stroboscopic 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.

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.

Identification of synthetic vowels based on selected vocal tract area functions.

The purpose of this study was to determine the degree to which synthetic vowel samples based on previously reported vocal tract area functions of eight speakers could be accurately identified by listeners. Vowels were synthesized with a wave-reflection type of vocal tract model coupled to a voice source. A particular vowel was generated by specifying an area function that had been derived from previous magnetic resonance imaging based measurements. The vowel samples were presented to ten listeners in a forced choice paradigm in which they were asked to identify the vowel. Results indicated that the vowels [i], [ae], and [u] were identified most accurately for all of speakers. The identification errors of the other vowels were typically due to confusions with adjacent vowels.

Auditory-Perceptual Rating of Connected Speech in Aphasia.

Purpose Auditory-perceptual assessment, in which trained listeners rate a large number of perceptual features of speech samples, is the gold standard for the differential diagnosis of motor speech disorders. The goal of this study was to investigate the feasibility of applying a similar, formalized auditory-perceptual approach to the assessment of language deficits in connected speech samples from individuals with aphasia. Method Twenty-seven common features of connected speech in aphasia were defined, each of which was rated on a 5-point scale. Three experienced researchers evaluated 24 connected speech samples from the AphasiaBank database, and 12 student clinicians evaluated subsets of 8 speech samples each. We calculated interrater reliability for each group of raters and investigated the validity of the auditory-perceptual approach by comparing feature ratings to related quantitative measures derived from transcripts and clinical measures, and by examining patterns of feature co-occurrence. Results Most features were rated with good-to-excellent interrater reliability by researchers and student clinicians. Most features demonstrated strong concurrent validity with respect to quantitative connected speech measures computed from AphasiaBank transcripts and/or clinical aphasia battery subscores. Factor analysis showed that 4 underlying factors, which we labeled Paraphasia, Logopenia, Agrammatism, and Motor Speech, accounted for 79% of the variance in connected speech profiles. Examination of individual patients' factor scores revealed striking diversity among individuals classified with a given aphasia type. Conclusion Auditory-perceptual rating of connected speech in aphasia shows potential to be a comprehensive, efficient, reliable, and valid approach for characterizing connected speech in aphasia.

THE USE OF A DUAL-TASK PARADIGM FOR ASSESSING SPEECH INTELLIGIBILITY IN CLIENTS WITH PARKINSON DISEASE.

Differences in the clinical and ecological manifestations of reduced intelligibility for individuals with dysarthria related to Parkinson disease (PD) have been reported in the literature. The current study explored whether a dual-task paradigm could be used during intelligibility testing to collect speech samples that were representative of functional performance. Intelligibility was calculated for four speakers with PD and four age-matched controls (CG) based on single-word, sentences, and monologue tasks recorded in single-and dual-task conditions and a spontaneous speech sample. In the dual-task condition, speakers produced the target speech sample and performed a simultaneous motor task, turning a nut on a bolt. No significant differences in intelligibility were found for the CG. For speakers with PD, differences between conditions were statistically significant for all speech tasks. Intelligibility scores in the dual-task condition were lower, with variability between tasks and speakers noted. There was a significant difference between scores for the monologue in the single-task condition and the spontaneous sample; however, there was no significant difference between the monologue in the dual-task condition and the spontaneous sample. Findings suggest that including a simple motor task during a clinical assessment may help elicit speech samples that are representative of a speaker's typical speech production.

Development of Velopharyngeal Closure for Vocalization During the First 2 Years of Life.

Purpose: The vocalizations of young infants often sound nasalized, suggesting that the velopharynx is open during the 1st few months of life. Whereas acoustic and perceptual studies seemed to support the idea that the velopharynx closes for vocalization by about 4 months of age, an aeromechanical study contradicted this (Thom, Hoit, Hixon, & Smith, 2006). Thus, the current large-scale investigation was undertaken to determine when the velopharynx closes for speech production by following infants during their first 2 years of life. Method: This longitudinal study used nasal ram pressure to determine the status of the velopharynx (open or closed) during spontaneous speech production in 92 participants (46 male, 46 female) studied monthly from age 4 to 24 months. Results: The velopharynx was closed during at least 90% of the utterances by 19 months, though there was substantial variability across participants. When considered by sound category, the velopharynx was closed from most to least often during production of oral obstruents, approximants, vowels (only), and glottal obstruents. No sex effects were observed. Conclusion: Velopharyngeal closure for spontaneous speech production can be considered complete by 19 months, but closure occurs earlier for speech sounds with higher oral pressure demands.