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Previously, we demonstrated a strong correlation between the amplitude of human speech and the emission rate of micron-scale expiratory aerosol particles, which are believed to play a role in respiratory disease transmission. To further those findings, here we systematically investigate the effect of different 'phones' (the basic sound units of speech) on the emission of particles from the human respiratory tract during speech. We measured the respiratory particle emission rates of 56 healthy human volunteers voicing specific phones, both in isolation and in the context of a standard spoken text. We found that certain phones are associated with significantly higher particle production; for example, the vowel /i/ (\"need,\" \"sea\") produces more particles than /ɑ/ (\"saw,\" \"hot\") or /u/ (\"blue,\" \"mood\"), while disyllabic words including voiced plosive consonants (e.g., /d/, /b/, /g/) yield more particles than words with voiceless fricatives (e.g., /s/, /h/, /f/). These trends for discrete phones and words were corroborated by the time-resolved particle emission rates as volunteers read aloud from a standard text passage that incorporates a broad range of the phones present in spoken English. Our measurements showed that particle emission rates were positively correlated with the vowel content of a phrase; conversely, particle emission decreased during phrases with a high fraction of voiceless fricatives. Our particle emission data is broadly consistent with prior measurements of the egressive airflow rate associated with the vocalization of various phones that differ in voicing and articulation. These results suggest that airborne transmission of respiratory pathogens via speech aerosol particles could be modulated by specific phonetic characteristics of the language spoken by a given human population, along with other, more frequently considered epidemiological variables.

Purpose: We explored the reliability and validity of 2 quantitative approaches to document presence and severity of speech properties associated with apraxia of speech (AOS). Method: A motor speech evaluation was administered to 39 individuals with aphasia. Audio-recordings of the evaluation were presented to 3 experienced clinicians to determine AOS diagnosis and to rate severity of 11 speech dimensions. Additionally, research assistants coded 11 operationalized metrics of articulation, fluency, and prosody in the same speech samples and in recordings from 20 neurologically healthy participants. Results: Agreement among the 3 clinicians was limited for both AOS diagnosis and perceptual scaling, but inter-observer reliability for the operationalized metrics was strong. The relationships between most operationalized metrics and mean severity ratings for corresponding perceptual dimensions were moderately strong and statistically significant. Both perceptual scaling and operationalized quantification approaches were sensitive to the presence or absence of AOS. Conclusions: Perceptual scaling and operationalized metrics are promising quantification techniques that can help establish diagnostic transparency for AOS. However, because satisfactory reliability cannot be assumed for scaling techniques, effective training and calibration procedures should be implemented. Operationalized metrics show strong potential for enhancing diagnostic objectivity and sensitivity.

The aim of the current study was to survey if vowel articulation in speakers with Parkinson's disease (PD) shows specific changes in the course of the disease. 67 patients with PD (42 male) and 40 healthy speakers (20 male) were tested and retested after an average time interval of 34 months. Participants had to read a given text as source for subsequent calculation of the triangular vowel space area (tVSA) and vowel articulation index (VAI). Measurement of tVSA and VAI were based upon analysis of the first and second formant of the vowels /α/, /i/and /u/ extracted from defined words within the text. At first visit, VAI values were reduced in male and female PD patients as compared to the control group, and showed a further decrease at the second visit. Only in female Parkinsonian speakers, VAI was correlated to overall speech impairment based upon perceptual impression. VAI and tVSA were correlated to gait impairment, but no correlations were seen between VAI and global motor impairment or overall disease duration. tVSA showed a similar reduction in the PD as compared to the control group and was also found to further decline between first and second examination in female, but not in male speakers with PD. Measurement of VAI seems to be superior to tVSA in the description of impaired vowel articulation and its further decline in the course of the disease in PD. Since impairment of vowel articulation was found to be independent from global motor function but correlated to gait dysfunction, measurement of vowel articulation might have a potential to serve as a marker of axial disease progression.

Purpose: In this investigation, the authors determined the strength of association between tongue kinematic and speech acoustics changes in response to speaking rate and loudness manipulations. Performance changes in the kinematic and acoustic domains were measured using two aspects of speech production presumably affecting speech clarity: phonetic specification and variability. Method: Tongue movements for the vowels /ia/ were recorded in 10 healthy adults during habitual, fast, slow, and loud speech using three-dimensional electromagnetic articulography. To determine articulatory-to-acoustic relations for phonetic specification, the authors correlated changes in lingual displacement with changes in acoustic vowel distance. To determine articulatory-to-acoustic relations for phonetic variability, the authors correlated changes in lingual movement variability with changes in formant movement variability. Results: A significant positive linear association was found for kinematic and acoustic specification but not for kinematic and acoustic variability. Several significant speaking task effects were also observed. Conclusion: Lingual displacement is a good predictor of acoustic vowel distance in healthy talkers. The weak association between kinematic and acoustic variability raises questions regarding the effects of articulatory variability on speech clarity and intelligibility, particularly in individuals with motor speech disorders.

Purpose: The purpose of this longitudinal study was to examine the effect of time and sentence length on speech rate and its characteristics, articulation rate and pauses, within 2 groups of children with cerebral palsy (CP). Method: Thirty-four children with CP, 18 with no speech motor involvement and 16 with speech motor involvement, produced sentences of varying lengths at 3 time points that were 1 year apart (mean age = 56 months at first time point). Dependent measures included speech rate, articulation rate, proportion of time spent pausing, and average number and duration of pauses. Results: There were no significant effects of time. For children with no speech motor involvement, speech rate increased with longer sentences due to increased articulation rate. For children with speech motor involvement, speech rate did not change with sentence length due to significant increases in the proportion of time spent pausing and average number of pauses in longer sentences. Conclusions: There were no significant age-related differences in speech rate in children with CP regardless of group membership. Sentence length differentially impacted speech rate and its characteristics in both groups of children with CP. This may be due to cognitive-linguistic and/or speech motor control factors.

Purpose: To determine if speech error patterns in preschoolers with speech sound disorders (SSDs) predict articulation and phonological awareness (PA) outcomes almost 4 years later. Method: Twenty-five children with histories of preschool SSDs (and normal receptive language) were tested at an average age of 4;6 (years;months) and were followed up at age 8;3. The frequency of occurrence of preschool distortion errors, typical substitution and syllable structure errors, and atypical substitution and syllable structure errors was used to predict later speech sound production, PA, and literacy outcomes. Results: Group averages revealed below-average school-age articulation scores and low-average PA but age-appropriate reading and spelling. Preschool speech error patterns were related to school-age outcomes. Children for whom greater than 10% of their speech sound errors were atypical had lower PA and literacy scores at school age than children who produced less than 10% atypical errors. Preschoolers who produced more distortion errors were likely to have lower school-age articulation scores than preschoolers who produced fewer distortion errors. Conclusion: Different preschool speech error patterns predict different school-age clinical outcomes. Many atypical speech sound errors in preschoolers may be indicative of weak phonological representations, leading to long-term PA weaknesses. Preschoolers' distortions may be resistant to change over time, leading to persisting speech sound production problems. (Contains 4 tables, 2 figures and 1 footnote.)

Purpose: We aimed to develop normative growth curves for articulation rate during sentence repetition for typically developing children. Our primary goal was the development of quantile/percentile growth curves so that typical variation in articulation rate with age could be estimated. We also estimated when children became adultlike in their articulation rate, and we examined the contributions of age and utterance length to articulation rate. Method: This cross-sectional study involved collection of in-person speech samples from 570 typically developing children (297 girls; 273 boys) who passed speech, language, and hearing screening measures. Pauses greater than 150 ms in duration were removed from the samples, and articulation rate was measured in syllables per second (sps). Results: Articulation rate reliably increased with age and utterance length. Rate in all key percentiles increased with age. The median rate (50th percentile) increased from 2.7 sps at 36 months to 3.3 sps at 96 months. The 5th percentile increased from 2.3 to 3.1 sps over the same age range. Using 3.2 sps as a benchmark for adultlike speech, we found the 25th, 50th, and 75th percentiles reached adultlike rates at 99, 75, and 53 months, respectively. Conclusions: Articulation rate increases from early childhood into middle childhood, and it is generally adultlike by 10 years of age. Variability in articulation rate among typical children was substantial. Implications for prior research and for clinical usage are discussed.

Purpose: The primary purpose of this study was to examine the effect of sentence length on speech rate and its characteristics, articulation rate and pauses, in typically developing children. Method: Sixty-two typically developing children between the ages of 10 and 14 years repeated sentences varying in length from two to seven words. Dependent variables included speech rate (syllables per second), articulation rate (syllables per second), and proportion of time spent pausing. Results: Speech rate and articulation rate significantly increased with increases in sentence length, but proportion of time spent pausing did not increase with sentence length. There were no significant main effects of age. Conclusions: This is the first study to suggest that sentence length differentially impacts the component parts of speech rate, articulation rate and pause time. Increases in sentence length led to increases in speech rate, primarily due to increases in articulation rate and not increases in pause time. Articulation rate appears to be highly sensitive to the impact of sentence length, while a higher cognitive-linguistic load may be required to see sentence length effects on pause time.

Purpose: As a class, fricatives are more \"resistant\" to consonant-vowel coarticulation than other English sounds. This study investigates the relative coarticulatory resistance of /[voiceless dental fricative], s, [voiceless palato-alveolar fricative]/ in child and adult speech to better understand the acquisition of individuated speech sounds. Method: Ten 5-year-old children, seven 8-year-old children, and nine college-age adults produced [[schwa]FV] sequences in carrier phrases, where F was /[voiceless dental fricative]/, /s/, or /[voiceless palato-alveolar fricative]/ and V was /ae/, /i/, or /u/. In Experiment 1, coarticulation was perceptually indexed: 65 adults predicted the target stressed vowel based on forward-gated audiovisual speech samples for a subset of four speakers from each age group. In Experiment 2, dynamic spectral measures of the /[schwa]FV/ sequences were analyzed using smoothing spline analysis of variance to again test for vowel effects on fricative articulation across age groups. Results: The perceptual results indicated that fricatives blocked vowel-vowel coarticulation across speaker age groups. Contrary to expectation, vowels were most accurately predicted when F was /s/ and not when it was /[voiceless palato-alveolar fricative]/ or /[voiceless dental fricative]/ across age groups. Acoustic results indicated the expected biomechanically motivated /[voiceless palato-alveolar fricative]/ > /s/ > /[voiceless dental fricative]/ coarticulatory resistance hierarchy in adults' speech. By contrast, /[voiceless palato-alveolar fricative]/ > /s/ were similarly influenced by context in 8-year-olds' speech, and the results from 5-year-olds' speech suggested an influence of order of acquisition in that /[voiceless dental fricative]/ was surprisingly resistant to coarticulation. Conclusion: The study results are taken to suggest that a temporal constraint on fricative articulation interacts with biomechanical constraints during development to influence patterns of coarticulation in school-age children's speech.