Acoustic characteristics of /s/ in adolescents

Differential spectral characteristics of the Spanish fricative /s/ in the articulation of individuals with dysarthria and apraxia of speech

PURPOSE

This study examines whether there are differences in the speech of speakers with dysarthria, speakers with apraxia and healthy speakers in spectral acoustic measures during production of the central-peninsular Spanish alveolar sibilant fricative /s/.

METHOD

To this end, production of the sibilant was analyzed in 20 subjects with dysarthria, 8 with apraxia of speech and 28 healthy speakers. Participants produced 12 sV(C) words. The variables compared across groups were the fricative's spectral amplitude difference (AmpD) and spectral moments in the temporal midpoint of fricative execution.

RESULTS

The results indicate that individuals with dysarthria can be distinguished from healthy speakers in terms of the spectral characteristics AmpD, standard deviation (SD), center of gravity (CoG) and skewness, the last two in context with unrounded vowel, while no differences in kurtosis were detected. Participants with AoS group differ significantly from healthy speaker group in AmpD, SD and CoG and Kurtosis, the first one followed unrounded vowel and the latter two followed by rounded vowels. In addition, speakers with apraxia of speech group returned significant differences with respect to speakers with dysarthria group in AmpD, CoG and skewness.

CONCLUSIONS

The differences found between the groups in the measures studied as a function of the type of vowel context could provide insights into the distinctive manifestations of motor speech disorders, contributing to the differential diagnosis between apraxia and dysarthria in motor control processes.

Spectral analysis of strident fricatives in cisgender and transfeminine speakersa)

The spectral features of /s/ and /ʃ/ carry important sociophonetic information regarding a speaker's gender. Often, gender is misclassified as a binary of male or female, but this excludes people who may identify as transgender or nonbinary. In this study, we use a more expansive definition of gender to investigate the acoustics (duration and spectral moments) of /s/ and /ʃ/ across cisgender men, cisgender women, and transfeminine speakers in voiced and whispered speech and the relationship between spectral measures and transfeminine gender expression. We examined /s/ and /ʃ/ productions in words from 35 speakers (11 cisgender men, 17 cisgender women, 7 transfeminine speakers) and 34 speakers (11 cisgender men, 15 cisgender women, 8 transfeminine speakers), respectively. In general, /s/ and /ʃ/ center of gravity was highest in productions by cisgender women, followed by transfeminine speakers, and then cisgender men speakers. There were no other gender-related differences. Within transfeminine speakers, /s/ and /ʃ/ center of gravity and skewness were not related to the time proportion expressing their feminine spectrum gender or their Trans Women Voice Questionnaire scores. Taken together, the acoustics of /s/ and /ʃ/ may signal gender group identification but may not account for within-gender variation in transfeminine gender expression.

The Acoustic and Perceptual Correlates of Gender in Children's Voices

PURPOSE

This study investigates the perceptual and acoustic correlates of gender in prepubertal voices. The study is part of a longitudinal project analyzing recordings of circa 60 German primary school children from the first to fourth grades (6- to 10-year-olds).

METHOD

Spontaneous and content-controlled audio recordings were made of 62 first-grade children (29 girls, 33 boys; age: 6- to 7-year-olds) from two German primary schools. Information on gender conformity was also recorded. A total of 167 listeners judged the gender of the voices on a 7-point scale. The results of the listening experiments and gender conformity ratings were related to a range of typical acoustic parameters.

RESULTS

Measures of self-reported gender conformity differ significantly between the boys and the girls. Sixteen of the 62 children show unambiguous gender attributions in the listening experiment. A hierarchical cluster analysis including gender perception, gender conformity, and acoustic parameters shows four different types of speakers. Two multiple regression models revealed a significant main effect of fundamental frequency on the gender perception ratings of the listening experiment across and within gender. Significant correlations were found between the center of gravity and skewness of the sibilants and gender conformity, especially for the male speakers.

CONCLUSIONS

Fundamental frequency plays an important role in influencing perceptual judgments, whereas sibilant spectra are correlated with gender conformity. In further listening experiments, we will examine in more detail the role of individual acoustic parameters and analyze how the vocal expression of gender and gender conformity in individual children develops before reaching puberty.

Intra- and inter-speaker variation in eight Russian fricativesa)

Acoustic variation is central to the study of speaker characterization. In this respect, specific phonemic classes such as vowels have been particularly studied, compared to fricatives. Fricatives exhibit important aperiodic energy, which can extend over a high-frequency range beyond that conventionally considered in phonetic analyses, often limited up to 12 kHz. We adopt here an extended frequency range up to 20.05 kHz to study a corpus of 15 812 fricatives produced by 59 speakers in Russian, a language offering a rich inventory of fricatives. We extracted two sets of parameters: the first is composed of 11 parameters derived from the frequency spectrum and duration (acoustic set) while the second is composed of 13 mel frequency cepstral coefficients (MFCCs). As a first step, we implemented machine learning methods to evaluate the potential of each set to predict gender and speaker identity. We show that gender can be predicted with a good performance by the acoustic set and even more so by MFCCs (accuracy of 0.72 and 0.88, respectively). MFCCs also predict individuals to some extent (accuracy = 0.64) unlike the acoustic set. In a second step, we provide a detailed analysis of the observed intra- and inter-speaker acoustic variation.

Differences in Sibilant Perception between Gender Expansive and Cisgender Individuals

Acoustic cues of voice gender influence not only how people perceive the speaker's gender (e.g., whether that person is a man, woman, or non-binary) but also how they perceive certain phonemes produced by that person. One such sociophonetic cue is the [s]/[ʃ] distinction in English; which phoneme is perceived depends on the perceived gender of the speaker. Recent research has shown that gender expansive people differ from cisgender people in their perception of voice gender and thus, this could be reflected in their categorization of sibilants. Despite this, there has been no research to date on how gender expansive people categorize sibilants. Furthermore, while voice gender expression is often discussed within a biological context (e.g., vocal folds), voice extends to those who use other communication methods. The current study fills this gap by explicitly recruiting people of all genders and asking them to perform a sibilant categorization task using synthetic voices. The results show that cisgender and gender expansive people perceive synthetic sibilants differently, especially from a "nonbinary" synthetic voice. These results have implications for developing more inclusive speech technology for gender expansive individuals, in particular for nonbinary people who use speech-generating devices.

Alternatives to moments for characterizing fricatives: Reconsidering Forrest et al. (1988)

Means of characterizing acoustic signals of fricatives with a few parameters have long been sought. When Forrest, Weismer, Milenkovic, and Dougall [(1988) J. Acoust. Soc. Am. 84, 115-123] described their system of treating spectra as probability density functions and computing the first four spectral moments, others quickly adopted their clearly described method, although it did not distinguish /f/ and /θ/. Various problems with their method are described, including the lack of spectral averaging, the necessity of normalizing the amplitude, and correlation between pairs of moments. Even when these issues are rectified by alternative methods, the fact remains that moments are not ideal descriptors because they can only describe departures from the shape of a normal Gaussian distribution. Fricative spectra, particularly of non-sibilants, are often quite dissimilar in shape from Gaussians. Furthermore, shape descriptors do not lend themselves to direct inferences about the production variables that caused the acoustic effects. Here, alternative parameters are defined, it is shown how to adapt them to specific experimental conditions, and tests of efficacy are proposed. These parameters are strongly linked to the articulatory and aerodynamic variables that underlie fricative production.

Acoustic and Perceptual Characteristics of Mandarin Speech in Gay and Heterosexual Male Speakers

This study investigated acoustic and perceptual characteristics of Mandarin speech produced by gay and heterosexual male speakers. Acoustic analysis of monosyllabic words showed significant differences between the two groups in voice fundamental frequency (F0), F1 of low vowel, and duration of aspiration/frication in consonants. The acoustic patterns on F0, formants, and center of gravity as well as spectral skewness of /s/ differed from those reported for Western languages like American English, which could be interpreted from a sociopsychological point of view based on different acceptability of gay identity in the two societies. The results of a perceptual experiment revealed significant but weak correlations between the acoustic parameters and the score of perceived gayness, which was significantly higher on gay speech than on heterosexual male speech. Although the observed F0 and F1 patterns in Mandarin gay speech were opposite to the stereotype of gayness, gay identity can still be identified to some extent from speech due to the existence of other acoustic cues such as a longer fricative duration, which is not a stereotype of gayness but has been consistently observed in Mandarin and Western languages.

Resynthesis of Transmasculine Voices to Assess Gender Perception as a Function of Testosterone Therapy

PURPOSE

The goal of this study was to use speech resynthesis to investigate the effects of changes to individual acoustic features on speech-based gender perception of transmasculine voice samples following the onset of hormone replacement therapy (HRT) with exogenous testosterone. We hypothesized that mean fundamental frequency (f o) would have the largest effect on gender perception of any single acoustic feature.

METHOD

Mean f o, f o contour, and formant frequencies were calculated for three pairs of transmasculine speech samples before and after HRT onset. Sixteen speech samples with unique combinations of these acoustic features from each pair of speech samples were resynthesized. Twenty young adult listeners evaluated each synthesized speech sample for gender perception and synthetic quality. Two analyses of variance were used to investigate the effects of acoustic features on gender perception and synthetic quality.

RESULTS

Of the three acoustic features, mean f o was the only single feature that had a statistically significant effect on gender perception. Differences between the speech samples before and after HRT onset that were not captured by changes in f o and formant frequencies also had a statistically significant effect on gender perception.

CONCLUSION

In these transmasculine voice samples, mean f o was the most important acoustic feature for voice masculinization as a result of HRT; future investigations in a larger number of transmasculine speakers and on the effects of behavioral therapy-based changes in concert with HRT is warranted.

Acoustic-phonetic and auditory mechanisms of adaptation in the perception of sibilant fricatives

Listeners are highly proficient at adapting to contextual variation when perceiving speech. In the present study, we examined the effects of brief speech and nonspeech contexts on the perception of sibilant fricatives. We explored three theoretically motivated accounts of contextual adaptation, based on phonetic cue calibration, phonetic covariation, and auditory contrast. Under the cue calibration account, listeners adapt by estimating a talker-specific average for each phonetic cue or dimension; under the cue covariation account, listeners adapt by exploiting consistencies in how the realization of speech sounds varies across talkers; under the auditory contrast account, adaptation results from (partial) masking of spectral components that are shared by adjacent stimuli. The spectral center of gravity, a phonetic cue to fricative identity, was manipulated for several types of context sound: /z/-initial syllables, /v/-initial syllables, and white noise matched in long-term average spectrum (LTAS) to the /z/-initial stimuli. Listeners' perception of the /s/-/ʃ/ contrast was significantly influenced by /z/-initial syllables and LTAS-matched white noise stimuli, but not by /v/-initial syllables. No significant difference in adaptation was observed between exposure to /z/-initial syllables and matched white noise stimuli, and speech did not have a considerable advantage over noise when the two were presented consecutively within a context. The pattern of findings is most consistent with the auditory contrast account of short-term perceptual adaptation. The cue covariation account makes accurate predictions for speech contexts, but not for nonspeech contexts or for the absence of a speech-versus-nonspeech difference.

Acoustic characteristics of Arabic pharyngealized obstruents in children with cochlear implants

Speech production of children with cochlear implants (CIs) is generally characterized by low intelligibility and reduced phoneme accuracy. However, limited research investigated their speech production using acoustic measures. The current study examined voice onset time (VOT) for pharyngealized plosives [t,d], and spectral moments and noise duration for pharyngealized fricatives [s,ð] produced by Arabic speaking children with CIs. Productions from children with CIs were compared with both chronological age-matched and hearing experience-matched normal hearing children. Results showed that children with CIs exhibited difficulty producing distinct VOTs between plosives and produced different spectral patterns of both fricatives relative to both comparison groups; however, they were able to produce an acoustic distinction between both fricatives. Children with CIs produced the fricatives with lower spectral mean and higher skewness and kurtosis. The sources for inter-group differences in the acoustic measures appeared to be due in part to limitations in the quality of auditory input provided by CIs as well as reduced motor experience in speech production. Results suggest that VOT and spectral moments are sensitive to changes in perceived sound quality. Spectral moments analysis appears to give details on subtle aspects of fricative production at the phonetic level beyond that available using perceptual judgments.

Sibilant production in Hebrew-speaking adults: Apical versus laminal

The Hebrew IPA charts describe the sibilants /s, z/ as 'alveolar fricatives', where the place of articulation on the palate is the alveolar ridge. The point of constriction on the tongue is not defined - apical (tip) or laminal (blade). Usually, speech and language pathologists (SLPs) use the apical placement in Hebrew articulation therapy. Some researchers and SLPs suggested that acceptable /s, z/ could be also produced with the laminal placement (i.e. the tip of the tongue approximating the lower incisors). The present study focused at the clinical level, attempting to determine the prevalence of these alternative points of constriction on the tongue for /s/ and /z/ in three different samples of Hebrew-speaking young adults (total n = 242), with typical articulation. Around 60% of the participants reported using the laminal position, regardless of several speaker-related variables (e.g. tongue-thrust swallowing, gender). Laminal production was more common in /s/ (than /z/), coda (than onset) position of the sibilant, mono- (than di-) syllabic words, and with non-alveolar (than alveolar) adjacent consonants. Experiment 3 revealed no acoustical differences between apical and laminal productions of /s/ and of /z/. From a clinical perspective, we wish to raise the awareness of SLPs to the prevalence of the two placements when treating Hebrew speakers, noting that tongue placements were highly correlated across sibilants. Finally, we recommend adopting a client-centred practice, where tongue placement is matched to the client. We further recommend selecting targets for intervention based on our findings, and separating between different prosodic positions in treatment.

A Diagnostic Marker to Discriminate Childhood Apraxia of Speech From Speech Delay: I. Development and Description of the Pause Marker

Purpose

The goal of this article (PM I) is to describe the rationale for and development of the Pause Marker (PM), a single-sign diagnostic marker proposed to discriminate early or persistent childhood apraxia of speech from speech delay.

Method

The authors describe and prioritize 7 criteria with which to evaluate the research and clinical utility of a diagnostic marker for childhood apraxia of speech, including evaluation of the present proposal. An overview is given of the Speech Disorders Classification System, including extensions completed in the same approximately 3-year period in which the PM was developed.

Results

The finalized Speech Disorders Classification System includes a nosology and cross-classification procedures for childhood and persistent speech disorders and motor speech disorders (Shriberg, Strand, & Mabie, 2017). A PM is developed that provides procedural and scoring information, and citations to papers and technical reports that include audio exemplars of the PM and reference data used to standardize PM scores are provided.

Conclusions

The PM described here is an acoustic-aided perceptual sign that quantifies one aspect of speech precision in the linguistic domain of phrasing. This diagnostic marker can be used to discriminate early or persistent childhood apraxia of speech from speech delay.

Compensatory Strategies in the Developmental Patterns of English /s/: Gender and Vowel Context Effects

PURPOSE

The developmental trajectory of English /s/ was investigated to determine the extent to which children's speech productions are acoustically fine-grained. Given the hypothesis that young children have adultlike phonetic knowledge of /s/, the following were examined: (a) whether this knowledge manifests itself in acoustic spectra that match the gender-specific patterns of adults, (b) whether vowel context affects the spectra of /s/ in adults and children similarly, and (c) whether children adopt compensatory production strategies to match adult acoustic targets.

METHOD

Several acoustic variables were measured from word-initial /s/ (and /t/) and the following vowel in the productions of children aged 2 to 5 years and adult controls using 2 sets of corpora from the Paidologos database.

RESULTS

Gender-specific patterns in the spectral distribution of /s/ were found. Acoustically, more canonical /s/ was produced before vowels with higher F1 (i.e., lower vowels) in children, a context where lingual articulation is challenging. Measures of breathiness and vowel intrinsic F0 provide evidence that children use a compensatory aerodynamic mechanism to achieve their acoustic targets in articulatorily challenging contexts.

CONCLUSION

Together, these results provide evidence that children's phonetic knowledge is acoustically detailed and gender specified and that speech production goals are acoustically oriented at early stages of speech development.

Ultrasound and acoustic analysis of sibilant fricatives in preadolescents and adults

This study describes the production of sibilant fricatives /s/ and /∫/, comparing Scottish English speaking preadolescent children with adults. The materials were the sequences /əCa/ and /əCi/ produced by 15 adults and 15 children aged between 10 and 12 years old. Quantitative analyses were carried out on both spectral information and on ultrasound imaging data on tongue shape, taken from nine successive time points during the fricative. The two groups of speakers were very similar to each other in the articulatory and acoustic characteristics distinguishing the two fricatives. Age-related differences in the fricative centroid measure occurred at consonant-vowel boundaries, with lower values in the preadolescents. Within-speaker variability was mostly similar across age groups, with the exception of the fricative centroid for /∫/, which was significantly more variable in preadolescents than in adults. Throughout the consonant duration, both groups consistently differentiated between the two consonants in both the fricative centroid and in one measure of tongue shape.

Gender difference in the affricate productions of young Seoul Korean speakers

This study explored gender-related differences in affricates' place of articulation of young Seoul Korean speakers. Word-initial and medial affricates before /a/ and /i/ collected from 42 adult Seoul speakers were compared with alveolar and palatalized fricatives in the same vowel conditions by examining spectral peak frequencies of the frication part of the consonants. Results showed evidence of gender differences in the acoustic realization of word-medial affricates, which implies a more anterior articulation in females' productions before /a/. Possibilities for sound change in affricates led by females or the use of anterior affricates as a socially indexed gender marker are discussed.

Developmental and gender-related trends of intra-talker variability in consonant production

This study investigates the effect of age and gender on the internal structure, cross-category distance, and discriminability of phonemic categories for two contrasts varying in fricative place of articulation (/s/-/∫/) and stop voicing (/b/-/p/) in word-initial tokens spoken by adults and normally developing children aged 9-14 yr. Vast between- and within-talker variability was observed with 16% of speakers exhibiting some degree of overlap between phonemic categories-a possible contribution to the range of talker intelligibility found in the literature. Females of all ages produced farther and thus more discriminable categories than males, although gender-marking for fricative between-category distance did not emerge until approximately 11 yr of age. Children produced farther yet also much more dispersed categories than adults with increasing discriminability with age, such that by age 13, children's categories were no less discriminable than those of adults. However, children's ages did not predict category distance or dispersion, indicating that convergence on adult-like category structure must occur later in adolescence.

Toward improved spectral measures of /s/: results from adolescents

PURPOSE

This article introduces theoretically driven acoustic measures of /s/ that reflect aerodynamic and articulatory conditions. The measures were evaluated by assessing whether they revealed expected changes over time and labiality effects, along with possible gender differences suggested by past work.

METHOD

Productions of /s/ were extracted from various speaking tasks from typically speaking adolescents (6 boys, 6 girls). Measures were made of relative spectral energies in low- (550-3000 Hz), mid- (3000-7000 Hz), and high-frequency regions (7000-11025 Hz); the mid-frequency amplitude peak; and temporal changes in these parameters. Spectral moments were also obtained to permit comparison with existing work.

RESULTS

Spectral balance measures in low-mid and mid-high frequency bands varied over the time course of /s/, capturing the development of sibilance at mid-fricative along with showing some effects of gender and labiality. The mid-frequency spectral peak was significantly higher in nonlabial contexts, and in girls. Temporal variation in the mid-frequency peak differentiated ±labial contexts while normalizing over gender.

CONCLUSIONS

The measures showed expected patterns, supporting their validity. Comparison of these data with studies of adults suggests some developmental patterns that call for further study. The measures may also serve to differentiate some cases of typical and misarticulated /s/.

Relationship between Occlusion and Lisping in Children with Cleft Lip and Palate

Introduction

The literature suggests that individuals with history of cleft lip and palate who present with midfacial growth deficiency are at higher risk of presenting lisping. The relationship between distortions during production of linguoalveolar fricative sounds and the severity of malocclusion, however, has not been established for the population with cleft.

Objective

To study the association between lisping and dental arch relationship.

Methodology

Speech samples and dental arch casts were obtained from 106 children with operated unilateral cleft lip and palate (UCLP) during the stage of mixed dentition and before orthodontic treatment. Videotaped productions of the phrase lu saci saiw sedul were rated by speech-language pathologists for the identification of lisping during [s]. Dental arch casts were rated by orthodontists using the Goslon Yardstick and the Five-Year Index to establish dental arch relationship.

Results

Multiple logistic regression showed no significant association between lisping and dento-occlusal index ( p = .802) and age ( p = .662). Substantial interjudge agreement during auditory-perceptual ratings was found (kappa = .63). Almost perfect agreement was found between orthodontists while establishing the dental arch relationship (kappa = .81).

Discussion

This study failed to reveal an association between lisping and dental arch relationship in children with operated UCLP. Multiple variables may play a role in determining occurrence of lisping, warranting further investigation.

A longitudinal acoustic study of the effects of the radial forearm free flap reconstruction on sibilants produced by tongue cancer patients

Acoustic properties of 980 tokens of sibilants /s, z, ƒ/ produced by 17 Canadian English-speaking female and male tongue cancer patients were studied. The patients had undergone tongue resection and tongue reconstruction with a radial forearm free flap (RFFF). The spectral moments (mean, skewness) and frication duration were analysed in connected speech samples produced before the tongue resection, and 1, 6 and 12 months after the surgery. The effects of radiation therapy (RT) and inclusion of the floor of the mouth (FOM) were also studied. Acoustic changes were observed only on alveolar sibilants /s, z/ such that speech was found to improve towards normal over the 1-year period. The reduction of acoustic distinction between /s, z/ and /ƒ/ was short term. A history of RT and involvement of the FOM had no differing effects on outcomes compared with non-RT or non-FOM. Variability between individuals was found, accentuating the speaker-specific abilities for adaptation, compensation and relearning after oral reconstruction.

Evaluating the spectral distinction between sibilant fricatives through a speaker-centered approach

This study was designed to examine the feasibility of using the spectral mean and/or spectral skewness to distinguish between alveolar and palato-alveolar fricatives produced by individual adult speakers of English. Five male and five female speaker participants produced 100 CVC words with an initial consonant /s/ or /ʃ/. The spectral mean and skewness were derived every 10 milliseconds throughout the fricative segments and plotted for all productions. Distinctions were examined for each speaker through visual inspection of these time history plots and statistical comparisons were completed for analysis windows centered 50 ms after the onset of the fricative segment. The results showed significant differences between the alveolar and palato-alveolar fricatives for both the mean and skewness values. However, there was considerable inter-speaker overlap, limiting the utility of the measures to evaluate the adequacy of the phonetic distinction. When the focus shifted to individual speakers rather than average group performance, only the spectral mean distinguished consistently between the two phonetic categories. The robustness of the distinction suggests that intra-speaker overlap in spectral mean between prevocalic /s/ and /ʃ/ targets may be indicative of abnormal fricative production and a useful measure for clinical applications.

Adaptation to an electropalatograph palate: acoustic, impressionistic, and perceptual data

PURPOSE

The purpose of this study was to evaluate adaptation to the electropalatograph (EPG) from the perspective of consonant acoustics, listener perceptions, and speaker ratings.

METHOD

Seven adults with typical speech wore an EPG and pseudo-EPG palate over 2 days and produced syllables, read a passage, counted, and rated their adaptation to the palate. Consonant acoustics, listener ratings, and speaker ratings were analyzed.

RESULTS

The spectral mean for the burst (/t/) and frication (/s/) was reduced for the first 60-120 min of wearing the pseudo-EPG palate. Temporal features (stop gap, frication, and syllable duration) were unaffected by wearing the pseudo-EPG palate. The EPG palate had a similar effect on consonant acoustics as the pseudo-EPG palate. Expert listener ratings indicated minimal to no change in speech naturalness or distortion from the pseudo-EPG or EPG palate. The sounds [see text] were most likely to be affected. Speaker self-ratings related to oral comfort, speech, tongue movement, appearance, and oral sensation were negatively affected by the presence of the palatal devices.

CONCLUSIONS

Speakers detected a substantial difference when wearing a palatal device, but the effects on speech were minimal based on listener ratings. Spectral features of consonants were initially affected, although adaptation occurred. Wearing an EPG or pseudo-EPG palate for approximately 2 hr results in relatively normal-sounding speech with acoustic features similar to a no-palate condition.

Toward diagnostic and phenotype markers for genetically transmitted speech delay

Converging evidence supports the hypothesis that the most common subtype of childhood speech sound disorder (SSD) of currently unknown origin is genetically transmitted. We report the first findings toward a set of diagnostic markers to differentiate this proposed etiological subtype (provisionally termed speech delay-genetic) from other proposed subtypes of SSD of unknown origin. Conversational speech samples from 72 preschool children with speech delay of unknown origin from 3 research centers were selected from an audio archive. Participants differed on the number of biological, nuclear family members (0 or 2+) classified as positive for current and/or prior speech-language disorder. Although participants in the 2 groups were found to have similar speech competence, as indexed by their Percentage of Consonants Correct scores, their speech error patterns differed significantly in 3 ways. Compared with children who may have reduced genetic load for speech delay (no affected nuclear family members), children with possibly higher genetic load (2+ affected members) had (a) a significantly higher proportion of relative omission errors on the Late-8 consonants; (b) a significantly lower proportion of relative distortion errors on these consonants, particularly on the sibilant fricatives /s/, /z/, and //; and (c) a significantly lower proportion of backed /s/ distortions, as assessed by both perceptual and acoustic methods. Machine learning routines identified a 3-part classification rule that included differential weightings of these variables. The classification rule had diagnostic accuracy value of 0.83 (95% confidence limits = 0.74-0.92), with positive and negative likelihood ratios of 9.6 (95% confidence limits = 3.1-29.9) and 0.40 (95% confidence limits = 0.24-0.68), respectively. The diagnostic accuracy findings are viewed as promising. The error pattern for this proposed subtype of SSD is viewed as consistent with the cognitive-linguistic processing deficits that have been reported for genetically transmitted verbal disorders.

Articulation rate and speech-sound normalization failure

Not all children with speech delay (SD) of unknown origin develop fully normal speech even with intervention. Many retain residual distortion errors into adolescence and ultimately into adulthood. The current study examined whether articulation rate distinguishes those children who retain residual errors from those who normalize. Two groups of speech-delayed children originally identified at preschool age were retested at age 9 years (the early follow-up group) and at age 12-16 years (the late follow-up group), respectively. No differences in articulation rate were observed at either test time in conversational speech between those children who continued to produce residual distortion errors (RE) compared to those children who had fully normalized speech (NSA). For the late follow-up group, children in the RE outcome group articulated speech at significantly slower rates than the children in the NSA outcome group in an embedded words task using both syllables per second and phones per second measures. Findings suggested that children with SD of unknown origin who fail to normalize may have relative speech-motor deficits and possibly deficits in language formulation skill. Alternatively, slower articulation rate in structured tasks may represent some sort of compensation for the continuing presence of speech-sound errors. Possible motivations for such compensation are discussed.

The perceptual consequences of within-talker variability in fricative production

The effect of talker and token variability on speech perception has engendered a great deal of research. However, most of this research has compared listener performance in multiple-talker (or variable) situations to performance in single-talker conditions. It remains unclear to what extent listeners are affected by the degree of variability within a talker, rather than simply the existence of variability (being in a multitalker environment). The present study has two goals: First, the degree of variability among speakers in their /s/ and /S/ productions was measured. Even among a relatively small pool of talkers, there was a range of speech variability: some talkers had /s/ and /S/ categories that were quite distinct from one another in terms of frication centroid and skewness, while other speakers had categories that actually overlapped one another. The second goal was to examine whether this degree of variability within a talker influenced perception. Listeners were presented with natural /s/ and /S/ tokens for identification, under ideal listening conditions, and slower response times were found for speakers whose productions were more variable than for speakers with more internal consistency in their speech. This suggests that the degree of variability, not just the existence of it, may be the more critical factor in perception.

Prevalence of speech delay in 6-year-old children and comorbidity with language impairment

We estimate the prevalence of speech delay (L.D. Shriberg, D. Austin, B. A. Lewis, J. L. McSweeny, & D. L. Wilson, 1997b) in the United States on the basis of findings from a demographically representative population subsample of 1,328 monolingual English-speaking 6-year-old children. All children's speech and language had been previously assessed in the "Epidemiology of Specific Language Impairment" project (see J. B. Tomblin et al., 1997), which screened 7,218 children in stratified cluster samples within 3 population centers in the upper Midwest. To assess articulation, the Word Articulation subtest of the Test of Language Development-2: Primary (Newcomer & Hammill, 1988) was administered to each of the 1,328 children, and conversational speech samples were obtained for a subsample of 303 (23%) children. The 6 primary findings are as follows: (a) The prevalence of speech delay in 6-year-old children was 3.8%; (b) speech delay was approximately 1.5 times more prevalent in boys (4.5%) than girls (3.1%); (c) cross-tabulations by sex, residential strata, and racial/cultural backgrounds yielded prevalence rates for speech delay ranging from 0% to approximately 9%; (d) comorbidity of speech delay and language impairment was 1.3%, 0.51% with Specific Language Impairment (SLI); (e) approximately 11-15% of children with persisting speech delay had SLI; and (f) approximately 5-8% of children with persisting SLI had speech delay. Discussion includes implications of findings for speech-language phenotyping in genetics studies.