Formant Dispersion Research Articles

Enunciation—An important factor in speech-to-text medical transcription systems

This study aims to explore the extent to which enunciation plays a crucial role in a speech-to-text (STT) system, especially when dealing with medical terminology. To achieve this, an audio dataset was recorded containing Polish medical terms and spoken diagnoses pronounced by healthcare professionals, including general practitioners and specialists in various fields such as cardiology, pulmonology, and radiology. The next step involved comprehensive acoustical and lexical analyses of the audio recordings. Features such as harmonic-to-noise ratio, spectral tilt, zero-crossing rate, formant dispersion, jitter, and shimmer were considered. Moreover, a transformer-based ASR (Automatic Speech Recognition) model was engaged in speech-to-text transcription. Several speech quality evaluation measures were used, such as WER (Word Error Rate), MER (Match Error Rate), WIL (Word Information Loss), WIP (Word Information Preserved), CER (Character Error Rate), etc. By measuring the STT model’s quality, it was possible to analyze the correlation between acoustical features and the expression style, as well as the speaker's distinctive vocabulary choices when reading acronyms. [Work supported by the Polish National Center for Research and Development (NCBR) project: “ADMEDVOICE-Adaptive intelligent speech processing system of medical personnel with the structuring of test results and support of therapeutic process,” no. INFOSTRATEG4/0003/2022.]

Acoustic Character Governing Variation in Normal, Benign, and Malignant Voices.

Benign and malignant vocal fold lesions (VFLs) are growths that occur on the vocal folds. However, the treatments for these two types of lesions differ significantly. Therefore, it is imperative to use a multidisciplinary approach to properly recognize suspicious lesions. This study aimed to determine the important acoustic characteristics specific to benign and malignant VFLs. The acoustic model of voice quality was utilized to measure various acoustic parameters in 157 participants, including individuals with normal, benign, and malignant conditions. The study comprised 62 female and 95 male participants (43 ± 10 years). Voice samples were collected at the Shanghai Eye, Ear, Nose, and Throat Hospital of Fudan University between May 2020 and July 2021. The acoustic variables of the participants were analyzed using Principal Component Analysis (PCA) to present important acoustic characteristics that are specific to normal vocal folds, benign VFLs, and malignant VFLs. The similarities and differences in acoustic factors were also studied for benign conditions including Reinke's edema, polyps, cysts, and leukoplakia. Using the PCA method, the components that accounted for the variation in the data were identified, highlighting acoustic characteristics in the normal, benign, and malignant groups. The analysis indicated that coefficients of variation in root mean square energy were observed solely within the normal group. Coefficients of variation in pitch (F0) were found to be significant only in benign voices, while higher formant frequencies and their variability were identified as contributors to the acoustic variance within the malignant group. The presence of formant dispersion (FD) as a weighted factor in PCA was exclusively noted in individuals with Reinke's edema. The amplitude ratio between subharmonics and harmonics (SHR) and its coefficients of variation were evident exclusively in the polyps group. In the case of voices with cysts, both pitch (F0) and coefficients of variation for FD were observed to contribute to variations. Additionally, higher formant frequencies and their coefficients of variation played a role in the acoustic variance among voices of patients with leukoplakia. Experimental evidence demonstrates the utility of the PCA method in the identification of vibrational alterations in the acoustic characteristics of voice affected by lesions. Furthermore, the PCA analysis has highlighted underlying acoustic differences between various conditions such as Reinke's edema, polyps, cysts, and leukoplakia. These findings can be used in the future to develop an automated malignant voice analysis algorithm, which will facilitate timely intervention and management of vocal fold conditions.

‘Beware, I am large and dangerous’ – human listeners can be deceived by dynamic manipulation of the indexical content of agonistic dog growls

Dishonest vocal signals about body size are rarely encountered, however, dogs are capable of modifying indexical information in their growls. This apparent acoustic body-size manipulation could be affected by the level of threat experienced by the dog. We tested whether this natural size manipulation actually affects how listeners assess the size of the dog, thus whether it could be considered as a successful indexical information manipulation. We requested human participants to assess dog growls, originally recorded when dogs encountered various ‘threatening strangers’ (of different sex, stature). The participants heard several sets of growl pairs, where they had to guess, which growl belonged to the ‘larger dog’. In the Control condition, dog growls originated from two different dogs in a pair; in the Test condition, growls of the same dog were presented pair by pair, always recorded in the presence of different threatening humans. Human listeners reliably picked the larger dog from two differently sized animals based on their growls alone. In the Test condition, participants thought that the dog was ‘larger’ when it was threatened by a female experimenter, and when the dog was growling at a larger sized human. We found that while growl length modulation was the main factor behind size-choice decisions in the case of female strangers, formant dispersion difference contributed the most when listeners chose which dog was the larger in the case of male opponents. Our results provide firsthand evidence of dogs’ functionally deceptive vocalizations towards humans, a phenomenon which has not been shown before in any interspecific scenario.

Voice pitch is negatively associated with sociosexual behavior in males but not in females.

Acoustic cues play a major role in social interactions in many animal species. In addition to the semantic contents of human speech, voice attributes - e.g., voice pitch, formant position, formant dispersion, etc. - have been proposed to provide critical information for the assessment of potential rivals and mates. However, prior studies exploring the association of acoustic attributes with reproductive success, or some of its proxies, have produced mixed results. Here, we investigate whether the mean fundamental frequency (F0), formant position (Pf), and formant dispersion (Df) - dimorphic attributes of the human voice - are related to sociosexuality, as measured by the Revised Sociosexual Orientation Inventory (SOI-R) - a trait also known to exhibit sex differences - in a sample of native Spanish-speaking students (101 males, 147 females). Analyses showed a significant negative correlation between F0 and sociosexual behavior, and between Pf and sociosexual desire in males but not in females. These correlations remained significant after correcting for false discovery rate (FDR) and controlling for age, a potential confounding variable. Our results are consistent with a role of F0 and Pf serving as cues in the mating domain in males but not in females. Alternatively, the association of voice attributes and sociosexual orientation might stem from the parallel effect of male sex hormones both on the male brain and the anatomical structures involved in voice production.

Structure and acoustics of the speech of verbal autistic preschoolers.

In this study, we report an extensive investigation of the structural language and acoustical specificities of the spontaneous speech of ten three- to five-year-old verbal autistic children. The autistic children were compared to a group of ten typically developing children matched pairwise on chronological age, nonverbal IQ and socioeconomic status, and groupwise on verbal IQ and gender on various measures of structural language (phonetic inventory, lexical diversity and morpho-syntactic complexity) and a series of acoustical measures of speech (mean and range fundamental frequency, a formant dispersion index, syllable duration, jitter and shimmer). Results showed that, overall, the structure and acoustics of the verbal autistic children's speech were highly similar to those of the TD children. Few remaining atypicalities in the speech of autistic children lay in a restricted use of different vocabulary items, a somewhat diminished morpho-syntactic complexity, and a slightly exaggerated syllable duration.

Penguins perceive variations of source- and filter-related vocal parameters of species-specific vocalisations.

Animal vocalisations encode a wide range of biological information about the age, sex, body size, and social status of the emitter. Moreover, vocalisations play a significant role in signalling the identity of the emitter to conspecifics. Recent studies have shown that, in the African penguin (Spheniscus demersus), acoustic cues to individual identity are encoded in the fundamental frequency (F0) and resonance frequencies (formants) of the vocal tract. However, although penguins are known to produce vocalisations where F0 and formants vary among individuals, it remains to be tested whether the receivers can perceive and use such information in the individual recognition process. In this study, using the Habituation-Dishabituation (HD) paradigm, we tested the hypothesis that penguins perceive and respond to a shift of ± 20% (corresponding to the natural inter-individual variation observed in ex-situ colonies) of F0 and formant dispersion (ΔF) of species-specific calls. We found that penguins were more likely to look rapidly and for longer at the source of the sound when F0 and formants of the calls were manipulated, indicating that they could perceive variations of these parameters in the vocal signals. Our findings provide the first experimental evidence that, in the African penguin, listeners can perceive changes in F0 and formants, which can be used by the receiver as potential cues for the individual discrimination of the emitter.

Women misjudge men’s physical characteristics based on vocal cues

ABSTRACT Voice is an important biological cue, which may reveal a significant amount of information about an individual. Particularly in males, it plays a crucial role in processes like male competition or sexual selection. Additionally, voice can provide a cue for body size assessment. This study investigates the relationship between male voice characteristics and physical features (assessed by women) and determines the accuracy of these assessments. Three groups of female judges assessed 60 male voices (20 different voices per group) across seven categories of male physical features: height, body fat, musculature, body shape, hirsuteness, age and strength. Recordings of five vowels and sentence and number of anthropometric measurements were made for each of the studied men. Intra- and extragroup agreement of assessments of men’s physical characteristics was demonstrated. Men with lower fundamental frequency (F0 ) and lower formant dispersion (Df ) values were perceived as being heavier, older, stronger and more likely to have chest hair. However, across all the analysed fields of assessment, no accuracy was registered between estimates and men’s actual physical characteristics. These findings suggest that females were guided by stereotypes in their assessment of men’s appearance from voice alone. We propose the size exaggeration hypothesis as an explanation of this phenomenon

Within- versus between-speaker acoustic variability in Thai

This paper continues our studies of acoustic variability in voice between and within speakers. Previous work indicates that acoustic variability is characterized by the balance between high-frequency harmonic and inharmonic energy in the voice (measured using cepstral peak prominence) and by formant dispersion, regardless of the speaker’s sex, native language, or speaking style. Our recent investigation of the language effect on voice variability surveyed three languages, English, Korean, and White Hmong, which form an organized subset with respect to their linguistic use of F0 and the phonological status of phonation quality. The cross-linguistic comparisons revealed a second tier of language-specific variability that reflects features of the phonology of each language. The present paper adds a tone language, Thai, to the mix. Samples of read speech from fifty Thai speakers (33F, 17M) were evaluated as in our previous studies. Results revealed that variability in Thai voices is primarily accounted for by the same biologically relevant measures observed globally, and further shaped by the language-specific use of F0. These data further support our hypothesis that acoustic variability in voice is governed first by biological factors, secondly by language-specific, cultural factors, and finally by idiosyncrasies of an individual’s anatomy and personal speaking style.

Acoustical impacts of blindness on speech production strategies linked to Lombard speech and audiovisual interaction

This paper investigates the acoustical correlates of Lombard speech and audiovisual interaction, in blind and sighted adults. Ten blind and nine sighted adults were recorded while producing repetitions of the French vowels /i/, /u/, /a/ in a “pVp” context. Sentences were produced under four conditions, varying in terms of interaction type (whether the speaker could be heard and seen—audiovisual interaction—or only heard— auditory interaction—by the interlocutor) and presence/absence of noise. Inter-vocalic and intra-vocalic formant dispersion as well as fundamental frequency (F0), intensity and vowel duration values were measured. Results of linear mixed effects models showed that blind speakers increased their inter-vocalic distances in noise, but decreased it when they were told they were seen by the interlocutor (audiovisual interaction). Blind speakers decreased F0 in the audiovisual conditions while sighted speakers increased F0 in noise. Finally, sighted speakers produced louder vowels in the noisy conditions and in the auditory interactive conditions. This pattern was only found for unrounded vowels in blind speakers. These results highlight the role of vision on speech production and show that sighted speakers likely use active strategies to enhance visual cues in audiovisual interactions, compared to auditory only interactions.

Assessment of the obesity based on voice perception

Human voice is an extremely important biological signal which contains information about sex, age, emotional state, health and physical features of a speaker. Estimating a physical appearance from a vocal cue can be an important asset for sciences including forensics and dietetics. Although there have been several studies focused on the relationships between vocal parameters and ratings of height, weight, age and musculature of a speaker, to our knowledge, there has not been a study examining the assessment of one’s BMI based on voice alone. The purpose of the current study was to determine the ability of female “Judges” to evaluate speakers’ (men and women) obesity and body fat distribution from their vocal cues. It has also been checked which voice parameters are key vocal cues in this assessment. The study material consisted of 12 adult speakers’ (6 women) voice recordings assessed by 87 “Judges” based on a 5-point graphic scale presenting body fat level and distribution (separately for men and women). For each speaker body height, weight, BMI, Visceral Fat Level (VFL, InBody 270) and acoustic parameters were measured. In addition, the accuracy of BMI category was verified. This study also aimed to determine which vocal parameters were cues for the assessment for men and women. To achieve it, two independent experiments were conducted: I: “Judges” had to choose one (obese) speaker from 3 voices (in 4 series); II: they were asked to rate body fat level of the same 12 speakers based on 5-point graphic scale. Obese speakers (i.e., BMI above 30) were selected correctly with the accuracy greater than predicted by chance (experiment I). By using a graphic scale, our study found that speakers exhibiting higher BMI were rated as fatter (experiment II). For male speakers the most important vocal predictors of the BMI were harmonics-to-noise ratio (HNR) and formant dispersion (Df); for women: formant spacing (Pf) and intensity (loudness). Human voice contains information about one’s increased BMI level which are hidden in some vocal cues.

Enhancement of formant regions in magnitude spectra to develop children’s KWS system in zero resource scenario

The mismatches due to pitch, speaking rate, formant dispersion and ambient noise deteriorate the performance of an automatic keyword spotting (KWS) system. The work presented in this paper aims at reducing the aforementioned mismatches through front-end signal processing. In the proposed approach, the short-term magnitude spectra (ST-MS) are firstly computed with a smaller frameshift and then averaged over the adjacent frames to enhance the formant regions. The formant regions in the ST-MS have a higher magnitude than the nearing frequency regions. Consequently, temporal averaging of ST-MS over adjacent frames suppresses the high-frequency variation due to pitch, and formant dispersion. Furthermore, the formant peaks can be more accurately detected from the temporal averaged ST-MS when compared to detection from the original ST-MS. The Mel frequency cepstral coefficients (MFCC) computed from the temporally averaged magnitude spectra (TAS-MFCC) are pitch robust compared to the MFCC, and MFCC extracted from the reported spectral smoothing approaches employing variational mode decomposition (VMD-MFCC), pitch adaptive cepstral truncation (PACT-MFCC) and single-pole filter (SPS-MFCC). Performance of TA-MFCC feature in mismatched test condition is further improved by appending five logarithmically compressed resonant peaks at least separated by 400 Hz, here this feature is termed as TAS-MFCC-ARP. The spectral peaks mostly represent the formants in ST-MS. The performances of the deep neural network-hidden Markov model-based children’s KWS system reported in this work show that the TAS-MFCC-ARP provides a relative performance improvement of 103.83% compared to MFCC. The performance of the KWS system is further improved by data-augmented training through duration modification.

Gender detection in children’s speech utterances for human-robot interaction

The human voice speech essentially includes paralinguistic information used in many real-time applications. Detecting the children’s gender is considered a challenging task compared to the adult’s gender. In this study, a system for human-robot interaction (HRI) is proposed to detect the gender in children’s speech utterances without depending on the text. The robot's perception includes three phases: Feature’s extraction phase where four formants are measured at each glottal pulse and then a median is calculated across these measurements. After that, three types of features are measured which are formant average (AF), formant dispersion (DF), and formant position (PF). Feature’s standardization phase where the measured feature dimensions are standardized using the z-score method. The semantic understanding phase is where the children’s gender is detected accurately using the logistic regression classifier. At the same time, the action of the robot is specified via a speech response using the text to speech (TTS) technique. Experiments are conducted on the Carnegie Mellon University (CMU) Kids dataset to measure the suggested system’s performance. In the suggested system, the overall accuracy is 98%. The results show a relatively clear improvement in terms of accuracy of up to 13% compared to related works that utilized the CMU Kids dataset.

Vocal Cues to Male Physical Formidability.

Animal vocalizations convey important information about the emitter, including sex, age, biological quality, and emotional state. Early on, Darwin proposed that sex differences in auditory signals and vocalizations were driven by sexual selection mechanisms. In humans, studies on the association between male voice attributes and physical formidability have thus far reported mixed results. Hence, with a view to furthering our understanding of the role of human voice in advertising physical formidability, we sought to identify acoustic attributes of male voices associated with physical formidability proxies. Mean fundamental frequency (F0), formant dispersion (Df), formant position (Pf), and vocal tract length (VTL) data from a sample of 101 male voices was analyzed for potential associations with height, weight, and maximal handgrip strength (HGS). F0 correlated negatively with HGS; Pf showed negative correlations with HGS, height and weight, whereas VTL positively correlated with HGS, height and weight. All zero-order correlations remained significant after controlling for false discovery rate (FDR) with the Benjamini–Hochberg method. After controlling for height and weight—and controlling for FDR—the correlation between F0 and HGS remained significant. In addition, to evaluate the ability of human male voices to advertise physical formidability to potential mates, 151 heterosexual female participants rated the voices of the 10 strongest and the 10 weakest males from the original sample for perceived physical strength, and given that physical strength is a desirable attribute in male partners, perceived attractiveness. Generalized linear mixed model analyses—which allow for generalization of inferences to other samples of both raters and targets—failed to support a significant association of perceived strength or attractiveness from voices alone and actual physical strength. These results add to the growing body of work on the role of human voices in conveying relevant biological information.

Linguistic and personal influences on speaker variability

Our previous studies examined the manner in which within- and between-speaker acoustic variability in voice follow patterns determined by biological factors, the language spoken, and individual idiosyncrasies. To date, we have analyzed data from speakers of English, Seoul Korean, and Hmong, which differ in whether they contrast phonation type and/or tone. We found several factors that consistently account for acoustic variability across languages, but also factors that vary with phonology. The present study adds Gujarati (which contrasts breathy with modal phonation) and Thai (a tone language without contrastive phonation) to this work. We hypothesize that F0 will emerge from analyses of Thai, as it did for Hmong and Korean (but not for English), and that differences in the amplitudes of lower harmonics will emerge for Gujarati, as occurred for Hmong, but not for English or Korean. We further hypothesize that two factors—the balance of high-frequency harmonic and inharmonic energy and formant dispersion—will emerge as the most important factors explaining acoustic variance for these new sets of speakers and languages, as they have in our previous studies. Such a result would be consistent with the view that speaker variability is governed by both biological and linguistic factors.

The acoustic bases of human voice identity processing in dogs

Speech carries identity-diagnostic acoustic cues that help individuals recognize each other during vocal–social interactions. In humans, fundamental frequency, formant dispersion and harmonics-to-noise ratio serve as characteristics along which speakers can be reliably separated. The ability to infer a speaker’s identity is also adaptive for members of other species (like companion animals) for whom humans (as owners) are relevant. The acoustic bases of speaker recognition in non-humans are unknown. Here, we tested whether dogs can recognize their owner’s voice and whether they rely on the same acoustic parameters for such recognition as humans use to discriminate speakers. Stimuli were pre-recorded sentences spoken by the owner and control persons, played through loudspeakers placed behind two non-transparent screens (with each screen hiding a person). We investigated the association between acoustic distance of speakers (examined along several dimensions relevant in intraspecific voice identification) and dogs’ behavior. Dogs chose their owner’s voice more often than that of control persons’, suggesting that they can identify it. Choosing success and time spent looking in the direction of the owner’s voice were positively associated, showing that looking time is an index of the ease of choice. Acoustic distance of speakers in mean fundamental frequency and jitter were positively associated with looking time, indicating that the shorter the acoustic distance between speakers with regard to these parameters, the harder the decision. So, dogs use these cues to discriminate their owner’s voice from unfamiliar voices. These findings reveal that dogs use some but probably not all acoustic parameters that humans use to identify speakers. Although dogs can detect fine changes in speech, their perceptual system may not be fully attuned to identity-diagnostic cues in the human voice.

Sound-meaning relations in Japanese Tanka

Abstract This study aimed to test sound-meaning relations in Japanese poetry. To this end, participants assessed the sentiments expressed in a random selection of Tanka (a specific form of Japanese poetry) on six bipolar scales comprising Evaluation (emotional valence), Potency (dominance), and Activity (arousal). The selected Tanka differed with regard to their average formant-dispersion (i.e., the distance between the first and second formant). Corroborating results of a previous study that tested the relation between formant dispersion and emotional tone in German poetry, results suggest that poems with an extremely low average formant dispersion have a significantly higher likelihood of expressing dominance and activity than poems with an extremely high formant dispersion. No significant differences regarding the Evaluation dimension were found.

Chest beats as an honest signal of body size in male mountain gorillas (Gorilla beringei beringei)

Acoustic signals that reliably indicate body size, which usually determines competitive ability, are of particular interest for understanding how animals assess rivals and choose mates. Whereas body size tends to be negatively associated with formant dispersion in animal vocalizations, non-vocal signals have received little attention. Among the most emblematic sounds in the animal kingdom is the chest beat of gorillas, a non-vocal signal that is thought to be important in intra and inter-sexual competition, yet it is unclear whether it reliably indicates body size. We examined the relationship among body size (back breadth), peak frequency, and three temporal characteristics of the chest beat: duration, number of beats and beat rate from sound recordings of wild adult male mountain gorillas. Using linear mixed models, we found that larger males had significantly lower peak frequencies than smaller ones, but we found no consistent relationship between body size and the temporal characteristics measured. Taken together with earlier findings of positive correlations among male body size, dominance rank and reproductive success, we conclude that the gorilla chest beat is an honest signal of competitive ability. These results emphasize the potential of non-vocal signals to convey important information in mammal communication.

Sound Predicts Meaning: Cross‐Modal Associations Between Formant Frequency and Emotional Tone in Stanzas

Research on the relation between sound and meaning in language has reported substantial evidence for implicit associations between articulatory-acoustic characteristics of phonemes and emotions. In the present study, we specifically tested the relation between the acoustic properties of a text and its emotional tone as perceived by readers. To this end, we asked participants to assess the emotional tone of single stanzas extracted from a large variety of poems. The selected stanzas had either an extremely high, a neutral, or an extremely low average formant dispersion. To assess the average formant dispersion per stanza, all words were phonetically transcribed and the distance between the first and second formant per vowel was calculated. Building on a long tradition of research on associations between sound frequency on the one hand and non-acoustic concepts such as size, strength, or happiness on the other hand, we hypothesized that stanzas with an extremely high average formant dispersion would be rated lower on items referring to Potency (dominance) and higher on items referring to Activity (arousal) and Evaluation (emotional valence). The results confirmed our hypotheses for the dimensions of Potency and Evaluation, but not for the dimension of Activity. We conclude that, at least in poetic language, extreme values of acoustic features of vowels are a significant predictor for the emotional tone of a text.

Dominance status and copulatory vocalizations among male stump-tailed macaques in Thailand

Male copulation calls sometimes play important roles in sexual strategies, attracting conspecific females or advertising their social status to conspecific males. These calls generally occur in sexually competitive societies such as harem groups and multi-male and multi-female societies. However, the call functions remain unclear because of limited availability of data sets that include a large number of male and female animals in naturalistic environments, particularly in primates. Here, we examined the possible function of male-specific copulation calls in wild stump-tailed macaques (Macaca arctoides) by analyzing the contexts and acoustic features of vocalizations. We observed 395 wild stump-tailed macaques inhabiting the Khao Krapuk Khao Taomor Non-Hunting Area in Thailand and recorded all occurrences of observed copulations. We counted 446 male-specific calls in 383 copulations recorded, and measured their acoustic characteristics. Data were categorized into three groups depending on their social status: dominant (alpha and coalition) males and non-dominant males. When comparing male status, alpha males most frequently produced copulation calls at ejaculation, coalition males produced less frequent calls than alpha males, and other non-dominant males rarely vocalized, maintaining silence even when mounting females. Acoustic analysis indicated no significant influence of status (alpha or coalition) on call number, bout duration, or further formant dispersion parameters. Our results suggest that male copulation calls of this species are social status-dependent signals. Furthermore, dominant males might actively transmit their social status and copulations to other male rivals to impede their challenging attacks, while other non-dominant males maintain silence to prevent the interference of dominants.

Vowel Acoustics and Speech Intelligibility in Young Adults With Down Syndrome

Purpose Speech production deficits and reduced intelligibility are frequently noted in individuals with Down syndrome (DS) and are attributed to a combination of several factors. This study reports acoustic data on vowel production in young adults with DS and relates these findings to perceptual analysis of speech intelligibility. Method Participants were eight young adults with DS as well as eight age- and gender-matched typically developing (TD) controls. Several different acoustic measures of vowel centralization and variability were applied to tokens of corner vowels (/ɑ/, /æ/, /i/, /u/) produced in common English words. Intelligibility was assessed for single-word productions of speakers with DS, by means of transcriptions from 14 adult listeners. Results Group differentiation was found for some, but not all, of the acoustic measures. Low vowels were more acoustically centralized and variable in speakers with DS than TD controls. Acoustic findings were associated with overall intelligibility scores. Vowel formant dispersion was the most sensitive measure in distinguishing DS and TD formant data. Conclusion Corner vowels are differentially affected in speakers with DS. The acoustic characterization of vowel production and its association with speech intelligibility scores within the DS group support the conclusion of motor control deficits in the overall speech impairment. Implications are discussed for effective treatment planning.