Healthy Talkers Research Articles

Improving intelligibility of dysarthric speech in noise for listeners with hearing loss

Noise reduction strategies based on time-frequency masking have been shown to provide substantial improvements in the intelligibility of speech in noise for both listeners with normal and impaired hearing. Previous studies on this type of noise reduction have involved intact, well-articulated speech spoken by healthy talkers (i.e., not disordered speech). However, the prevalence of speech disorders such as dysarthria is substantial, particularly in the aging population, which is highly susceptible to the impacts of hearing loss. We recently demonstrated the considerable impact of background noise on dysarthric speech as well as the effectiveness of time-frequency masking to improve the intelligibility of this disordered speech in noise for listeners with normal hearing (Borrie et al., 2023). Here, we present data on the feasibility of time-frequency masking to increase the intelligibility of dysarthric speech for listeners with sensorineural hearing impairment. Preliminary results indicate that the Ideal Quantized Mask, a method of time-frequency masking, significantly improves percent words correct scores of dysarthric speech in noise for listeners with hearing loss. Results will be discussed in relation to the specific impact of background noise on dysarthric speech, and the relationship between sensorineural hearing loss and dysarthric speech.

The impact of face masks on spectral acoustics of speech: Effect of clear and loud speech styles.

This study quantified the effects of face masks on spectral speech acoustics in healthy talkers using habitual, loud, and clear speaking styles. Harvard sentence lists were read aloud by 17 healthy talkers in each of the 3 speech styles without wearing a mask, when wearing a surgical mask, and when wearing a KN95 mask. Outcome measures included speech intensity, spectral moments, and spectral tilt and energy in mid-range frequencies which were measured at the utterance level. Masks were associated with alterations in spectral density characteristics consistent with a low-pass filtering effect, although the effect sizes varied. Larger effects were observed for center of gravity and spectral variability (in habitual speech) and spectral tilt (across all speech styles). KN95 masks demonstrated a greater effect on speech acoustics than surgical masks. The overall pattern of the changes in speech acoustics was consistent across all three speech styles. Loud speech, followed by clear speech, was effective in remediating the filtering effects of the masks compared to habitual speech.

Relationship between phoneme-level spectral acoustics and speech intelligibility in healthy speech: a systematic review

ABSTRACT This study aims to systematically review original articles investigating the link between spectral acoustic measures in healthy talkers and perceived speech intelligibility, according to the PRISMA guidelines. Twenty-two studies were retained. Eighteen papers investigated vowel acoustics, one studied glides and eight articles investigated consonants, mostly sibilants. Various spectral measures and intelligibility estimates were used. The following measures were shown to be linked to sub-lexical perceived speech intelligibility ratings: for vowels, steady-state F1 and F2 measures, the F1 range, the [i]-[U] F2 difference, F0-F1 and F1-F2 differences in [è-A] and [q-è], the vowel space area, the mean amount of formant movement, the vector length and the spectral change measure; for consonants, the centroid energy and the spectral peak in the [s]-sound, as well as the steady-state F1 offset frequency in vowels preceding [t] and [d].To conclude, as speech is highly variable even in healthy adult speakers, a better understanding of the imprecisions in healthy spontaneous speech will provide a more realistic baseline for the investigation of disordered speech. To date, no acoustic measure is able to predict speech intelligibility to a large extent. There is still extensive research to be carried out to identify relevant acoustic combinations that could account for perceived speech variations (e.g. vowel and consonant reductions) and to gather normative data from a large number of healthy speakers. To that end, speech-related terms (e.g. intelligibility, comprehensibility, severity) need to be clearly defined and methodologies described in sufficient details to allow for replication, cross-comparisons/meta-analyses and pooling of data. .

Effects of room acoustics on talkers: A use case for speech-acoustic signal processing in architectural acoustics

In the past, several room-acoustic parameters, recommendations, and standards have been developed with emphasis on accommodating the listener. Recent research has shown that talkers also respond to room acoustics via vocal adaptations. In fact, room acoustics may influence the development of voice disorders in occupational speech users. To evaluate the relationships between room acoustics and vocal parameters of healthy talkers, the authors of this presentation analyzed speech-acoustic signals under a variety of acoustical conditions. Vocal parameters were derived from recordings, and statistically significant effects of room acoustics were verified using mixed-model analysis of variance tests. Changes in reverberation time (T20), early decay time (EDT), clarity index (C50), speech transmission index (STI), and room gain (GRG) all showed highly correlated effects on certain vocal parameters, including speaking level standard deviation, speaking rate, and acoustic vocal quality index. The results show that as T20, EDT, and GRG increased, and as C50 and STI decreased, vocal parameters tended toward dysphonic phonation. These findings increase our understanding of the impact of room acoustics on vocal production, informing room design to help mitigate unhealthy vocal exertion and, by extension, voice problems. The study provides examples of how signal processing of speech signals benefits architectural-acoustics knowledge.

Variations of F2 range measures in mild dysarthria and healthy talkers

Diminished vocalic segments indexed by the extent, duration, and rate of change in the second formant (F2) are common in dysarthria and are known to reduce intelligibility in adults with multiple sclerosis (MS; Hartelius et al., 2010). When F2 range was measured over select sentences from a reading passage, results indicated that the F2 range may not be sensitive to mild dysarthria in MS (Rosen et al., 2008). However, measures of the F2 range should be further explored for sentences imposing greater speech-motor and cognitive-linguistic demands. As such, phonetic contexts requiring even small vocal tract movement may contribute to intelligibility for speakers with mild dysarthria in MS. Thus, this study will investigate the impact of sentence length and complexity on within-speaker variations of F2 movement and group differences for 12 adults with mild dysarthria in MS and 12 healthy talkers. Various F2 range measures shown to be sensitive to speech motor capabilities will be obtained from 11 audio-recorded sentences varying in length and complexity. The results of this study will provide a better understanding of the speech motor control capabilities of speakers with mild dysarthria with relatively preserved intelligibility in MS. [Work supported by ASH Foundation and the University at Buffalo MDRF.]Diminished vocalic segments indexed by the extent, duration, and rate of change in the second formant (F2) are common in dysarthria and are known to reduce intelligibility in adults with multiple sclerosis (MS; Hartelius et al., 2010). When F2 range was measured over select sentences from a reading passage, results indicated that the F2 range may not be sensitive to mild dysarthria in MS (Rosen et al., 2008). However, measures of the F2 range should be further explored for sentences imposing greater speech-motor and cognitive-linguistic demands. As such, phonetic contexts requiring even small vocal tract movement may contribute to intelligibility for speakers with mild dysarthria in MS. Thus, this study will investigate the impact of sentence length and complexity on within-speaker variations of F2 movement and group differences for 12 adults with mild dysarthria in MS and 12 healthy talkers. Various F2 range measures shown to be sensitive to speech motor capabilities will be obtained from 11 audio-record...

Effects of added absorption on the vocal exertions of talkers in a reverberant room

Occupational speech users such as schoolteachers develop voice disorders at higher rates than the general population. Previous research has suggested that room acoustics may influence these trends. The research reported in this paper utilized varying acoustical conditions in a reverberant room to assess the effects on vocal parameters of healthy talkers. Thirty-two participants were recorded while completing a battery of speech tasks under eight room conditions. Vocal parameters were derived from the recordings and the statistically significant effects of room acoustics were verified using mixed-model analysis of variance tests. Changes in reverberation time (T20), early decay time (EDT), clarity index (C50), speech transmission index (STI), and room gain (GRG) all showed highly correlated effects on certain vocal parameters, including speaking level standard deviation, speaking rate, and the acoustic vocal quality index. As T20, EDT, and GRG increased, and as C50 and STI decreased, vocal parameters showed tendencies toward dysphonic phonation. Empirically derived equations are proposed that describe the relationships between select room-acoustic parameters and vocal parameters. This study provides an increased understanding of the impact of room acoustics on voice production, which could assist acousticians in improving room designs to help mitigate unhealthy vocal exertion and, by extension, voice problems.

An Optimal Set of Flesh Points on Tongue and Lips for Speech-Movement Classification.

The authors sought to determine an optimal set of flesh points on the tongue and lips for classifying speech movements. The authors used electromagnetic articulographs (Carstens AG500 and NDI Wave) to record tongue and lip movements from 13 healthy talkers who articulated 8 vowels, 11 consonants, a phonetically balanced set of words, and a set of short phrases during the recording. We used a machine-learning classifier (support-vector machine) to classify the speech stimuli on the basis of articulatory movements. We then compared classification accuracies of the flesh-point combinations to determine an optimal set of sensors. When data from the 4 sensors (T1: the vicinity between the tongue tip and tongue blade; T4: the tongue-body back; UL: the upper lip; and LL: the lower lip) were combined, phoneme and word classifications were most accurate and were comparable with the full set (including T2: the tongue-body front; and T3: the tongue-body front). We identified a 4-sensor set--that is, T1, T4, UL, LL--that yielded a classification accuracy (91%-95%) equivalent to that using all 6 sensors. These findings provide an empirical basis for selecting sensors and their locations for scientific and emerging clinical applications that incorporate articulatory movements.

Acoustic characteristics of the Lombard effect from talkers with Parkinson’s disease

Speech production in noise elicits the Lombard effect, characterized by an increase in vocal effort. In talkers with Parkinson’s disease (PD), noisy environments are a stressor to speech production. Recently, the intelligibility of speech from PD talkers speaking in noisy (additive multi-talker babble) and reverberant environments was shown to be more sensitive to both factors than speech from healthy talkers [Kopf et al., ASHA 7387 (2013)]. The current study investigated the acoustic properties of speech and how they change in noise and reverberation for PD talkers compared to healthy talkers. Healthy talkers increased their level and fundamental frequency in additive noisy environments and, to a lesser degree, in reverberant environments. PD talkers also changed their level and fundamental frequency but to a more limited extent compared to healthy talkers. Additional changes in speech production (speaking rate, articulation range, and voice quality) were observed in individual talkers from both groups.

Articulatory Distinctiveness of Vowels and Consonants: A Data-Driven Approach

To quantify the articulatory distinctiveness of 8 major English vowels and 11 English consonants based on tongue and lip movement time series data using a data-driven approach. Tongue and lip movements of 8 vowels and 11 consonants from 10 healthy talkers were collected. First, classification accuracies were obtained using 2 complementary approaches: (a) Procrustes analysis and (b) a support vector machine. Procrustes distance was then used to measure the articulatory distinctiveness among vowels and consonants. Finally, the distance (distinctiveness) matrices of different vowel pairs and consonant pairs were used to derive articulatory vowel and consonant spaces using multidimensional scaling. Vowel classification accuracies of 91.67% and 89.05% and consonant classification accuracies of 91.37% and 88.94% were obtained using Procrustes analysis and a support vector machine, respectively. Articulatory vowel and consonant spaces were derived based on the pairwise Procrustes distances. The articulatory vowel space derived in this study resembled the long-standing descriptive articulatory vowel space defined by tongue height and advancement. The articulatory consonant space was consistent with feature-based classification of English consonants. The derived articulatory vowel and consonant spaces may have clinical implications, including serving as an objective measure of the severity of articulatory impairment.

A novel fixed-target task to determine articulatory speed constraints in persons with amyotrophic lateral sclerosis

Purpose The goal of this study was to determine if talkers with ALS are limited in their ability to increase lower lip and jaw speed at an early stage of the disease when their speaking rate and intelligibility are only minimally or not affected. Method A novel metronome paced fixed-target task was used to assess movement speed capacities during lower lip and jaw oscillations in seven talkers with ALS and seven age and gender matched controls. Results Lower lip peak speeds were significantly lower in talkers with mild ALS than in healthy talkers suggesting a lower lip speed constraint in talkers with mild ALS. Jaw peak speeds tended to be lower, but jaw displacements tended to be larger in talkers with mild ALS than in healthy talkers. Because greater speeds are typically expected for larger displacements, outcomes also suggest a jaw speed constraint in talkers with mild ALS. Conclusions Lower lip and jaw peak speeds may be sensitive measures to identify bulbar motor performance decline at an early stage of the disease when speaking rate and intelligibility are only minimally affected. Learning Outcomes: The reader will be able to explain two different articulatory strategies to increase speaking rate and understand why fast speech tasks and diadochokinetic pseudo-speech tasks are not suited to assess articulatory speed capacity in healthy and impaired talkers. The reader will also be able to explain how orofacial movement speed capacity can be tested using a fixed-target task and how ALS affects lower lip and jaw speed capacities during the early stages of the disease.

Articulatory-to-acoustic relations in response to speaking rate and loudness manipulations.

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. 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. 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. 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.

A kinematic investigation of anticipatory lingual movement in acquired apraxia of speech

Background: Apraxia of speech (AOS) is considered a disorder of speech planning or programming. Evidence for this stems from perceptual, acoustic, and electropalatographic investigations of articulation in AOS that revealed a delayed onset of anticipatory vowel gestures. Articulatory prolongation and syllable segregation have been attributed to a disturbance in anticipatory coarticulation. Aims: The aim of the current study was to investigate anticipatory lingual movement for consonantal gestures in AOS, and its impact on absolute and relative speech timing. Methods & Procedures: Tongue-tip movement and tongue-to-palate contact patterns were recorded for three speakers with AOS and a concomitant aphasia (age range = 35–63 years; M = 50.67 years; SD = 14.29) and five healthy talkers (age range = 29–65 years; M = 52.6 years; SD = 14.5) during the phrases “a scarlet” and “a sergeant”, using electromagnetic articulography (EMA) (AG-200 system) and electropalatography (EPG) (Reading Electropalatograph system). Anticipatory lingual movement and speech timing were analysed during the final C1VC/C2 syllable in each of these phrases, where C represented an alveolar or postalveolar consonant. Specifically, tongue-tip displacement was calculated from the onset of release to the end of release of C1 to provide an indication of anticipatory lingual movement. With respect to speech timing, absolute (i.e., duration from time of maximum contact for C1 to time of maximum contact for C2) and relative (i.e., absolute duration expressed as a function of total syllable duration) durational measures were recorded, as was the stability of each. The results recorded for each of the participants with AOS were individually compared to those obtained by the control group. Outcomes & Results: The EMA results indicated that two participants with AOS exhibited reduced anticipatory lingual movement (i.e., greater tongue-tip displacement) during repetitions of “sergeant”; however, all speakers produced a comparable tongue-tip displacement to that produced by the control group during the release of /l/ in “scarlet”. The EPG results indicated that absolute duration was significantly prolonged during the final syllables of both stimuli for each of the apraxic speakers. Equivocal results were reported for relative timing and temporal stability. Conclusions: The results provide some preliminary evidence of reduced anticipatory lingual movement in AOS, and have demonstrated that this can have a significant impact on absolute speech timing. However, measures of relative timing were suggestive of either unimpaired or more extensive coarticulation. Additional research is required to resolve this issue.

The Effect of Fundamental Frequency on the Intelligibility of Speech With Flattened Intonation Contours

To examine the effect of fundamental frequency (F0) on the intelligibility of speech with flattened F0 contours in noise. Participants listened to sentences produced by 2 female talkers in white noise. The listening conditions included the unmodified original sentences and sentences with resynthesized F0 that reflected the average low F0, the median F0, and the average high F0 of each talker's productions. The sentences with flattened F0 contours yielded poorer intelligibility than the unmodified ones, but the sentences with flattened F0 did not produce equivalent performance. The sentences with F0 contours flattened at the average low F0 yielded better performance than sentences at the median F0. The sentences with F0 flattened at the average high F0 yielded poorer performance than the sentences flattened at the median F0. F0 height accounted for only a small amount of the drop in speech understanding in speech with a flattened F0 in healthy talkers. Although this study used healthy talkers, the findings suggest that clinicians should focus on having clients produce speech with naturally varying F0; F0 height is a secondary factor in the drop in intelligibility seen in monotone speech for female talkers.

Estimating Mandibular Motion Based on Chin Surface Targets During Speech

The movement of the jaw during speech and chewing has frequently been studied by tracking surface landmarks on the chin. However, the extent to which chin motions accurately represent those of the underlying mandible remains in question. In this investigation, the movements of a pellet attached to the incisor of the mandible were compared with those of pellets attached to different regions of the chin. Ten healthy talkers served as participants. Three speaking contexts were recorded from each participant: word, sentence, and paragraph. Chin position errors were estimated by computing the standard distance between the mandibular incisor pellet and the chin pellets. Relative to the underlying mandible, chin pellets moved with an average absolute and relative error of 0.81 mm and 7.30%, respectively. The movements of chin and mandibular pellets were tightly coupled in time. The chin tracking errors observed in this investigation are considered acceptable for descriptive studies of oromotor behavior, particularly in situations where mandibular placements are not practical (e.g., young children or edentulous adults). The observed amount of error, however, may not be tolerable for fine-grained analyses of mandibular biomechanics. Several guidelines are provided for minimizing error associated with tracking surface landmarks on the chin.

Perception of Coarticulatory Information in Normal Speech and Dysarthria

This study addressed three research questions: (a) Can listeners use anticipatory vowel information in prevocalic consonants produced by talkers with dysarthria to identify the upcoming vowel? (b) Are listeners sensitive to interspeaker variation in anticipatory coarticulation during prevocalic consonants produced by healthy talkers and/or talkers with dysarthria, as measured by vowel identification accuracy? (c) Is interspeaker variation in anticipatory coarticulation reflected in measures of intelligibility? Stimuli included 106 CVC words produced by 20 speakers with either Parkinson's disease or multiple sclerosis or by 16 healthy controls characterized by an operationally defined normal, under, or over level of anticipatory vowel coarticulation. Ten listeners were presented with prevocalic consonants for identification of the vowel. Ten additional listeners judged single-word intelligibility. An analysis of variance was used to determine differences in vowel identification accuracy and intelligibility as a function of speaker group, coarticulation level, and vowel type. Listeners accurately identified vowels produced by all speaker groups from the aperiodic portion of prevocalic consonants, but interspeaker variations in strength of coarticulation did not strongly affect vowel identification accuracy or intelligibility. Listeners appear to be tuned to similar types of information in the acoustic speech stream irrespective of the source or speaker, and any perceptual effects of interspeaker variation in coarticulation are subtle.

Characteristics of the Lax Vowel Space in Dysarthria

It has been hypothesized that lax vowels may be relatively unaffected by dysarthria, owing to the reduced vocal tract shapes required for these phonetic events (G. S. Turner, K. Tjaden, & G. Weismer, 1995). It also has been suggested that lax vowels may be especially susceptible to speech mode effects (M. A. Picheny, N. I. Durlach, & L. D. Braida, 1986). Studies evaluating these suggestions are lacking, however. The present study was an initial investigation of the vowel space area formed by the lax vowels /Iota/, /epsilon/, and /upsilon/, occurring in a passage read in habitual, fast, and slow conditions by speakers with amyotrophic lateral sclerosis (ALS), speakers with Parkinson's disease (PD), and healthy controls. Vowel space areas for speakers with ALS but not speakers with PD differed from those for the appropriate control group. Thus, only the results for the PD group support the hypothesis that lax vowel space areas for speakers with dysarthria should be similar to those for neurologically normal talkers. Compared with the habitual condition, rate reduction was associated with an expanded vowel space area for all of the healthy talkers but for only about half of the speakers with dysarthria. In addition, about half of the speakers in each group demonstrated a reduced vowel space area for the fast condition relative to the habitual condition, although the statistical analyses indicated no difference in vowel space areas for the fast and habitual conditions. The current study therefore provides only limited support for the idea that lax vowels are highly susceptible to speech mode effects, at least when the speech modes under consideration include faster-than-normal and slower-than normal rates. Clinical implications are discussed.

Identification of 20-ms speech samples from normal and neurologically impaired talkers: Do coarticulation differences matter?

Prior studies of speech suggest that the extent of coarticulation varies both across and within talkers. Speakers sometime use average, high, or low amounts of coarticulation. The perceptual consequences of coarticulatory variability are not well understood, particularly for the speech of individuals with motor control disorders. In the current study, listeners heard the same 20-ms tokens that were used to calculate the degree of anticipatory coarticulation of the following vowel. Acoustic measures were made from the first 20 ms of stop consonants [k] or [t], or from a point 70 ms preceding the vowel in [s] productions. Healthy talkers, speakers with Multiple Sclerosis, and speakers with Parkinson’s disease produced the stimuli. Speech tokens included three degrees of anticipatory coarticulation: average, high, and low. The listeners’ task was to identify whether the vowels that followed the consonant were originally [i] or [u]. Results showed that identification accuracy was poorer for the current 20-ms tokens than for prior speech samples including all aperiodicity of consonants. Identification was poorest for [s] and best for [k] tokens. The speed of listener response gave some indication of the differing extents of coarticulation. Perceptual validity for the 20-ms measure of coarticulation is discussed.

Do listeners perceive coarticulatory differences for normal talkers and neurologically impaired talkers?

Speech production studies suggest that the extent of coarticulation varies across talkers. The extent of coarticulation may even vary for repetitions of the same utterance produced by a single talker. Thus, an utterance or talker could be characterized by an average degree of coarticulation, a high degree of coarticulation, or a low degree of coarticulation. The perceptual consequences, if any, of this coarticulatory variability are not well understood, particularly for individuals with speech motor control disorders. The current study examined whether the listeners’ speed and accuracy of vowel identification for naturally-produced CV sequences varied depending on the extent of anticipatory vowel coarticulation. Speakers and speech tokens included those characterized by an average degree of anticipatory coarticulation, a high degree of coarticulation, and a low degree of coarticulation. Healthy talkers, speakers with multiple sclerosis, and speakers with Parkinson’s disease produced the stimuli. Consonants in CV syllables beginning with /s/, /k/, or /t/ followed by the vowels /i/ or /u/ were excised and presented to listeners for identification of the following vowel. While identification accuracy may be high across speakers and stimuli, the speed of response should vary with extent of coarticulation, if listeners are sensitive to coarticulatory cues in the acoustic speech stream.

Characteristics of diadochokinesis in Parkinson’s Disease and Multiple Sclerosis

The current study applies a quantitative, acoustic analysis procedure for the study of rapid syllable productions outlined by Kent and colleagues [R. D. Kent et al., J. Med. Sp. Lang. Path. 7, 83–90 (1999)] to syllables produced by speakers with Parkinson’s Disease and Multiple Sclerosis. Neurologically healthy talkers will be studied for comparison purposes. Acoustic measures will be reported for syllable repetitions of /pə/, /tə/, and /kə/. Temporal measures will include syllable duration, syllable rate, and stop gap duration. The energy envelope of syllable repetitions will be quantified using measures of rms amplitude minima and maxima. Acoustic measures will be contrasted to determine the extent to which acoustic profiles of diadochokinesis distinguish hypokinetic dysarthria associated with Parkinson’s Disease, ataxic dysarthria secondary to Multiple Sclerosis, and spastic dysarthria secondary to Multiple Sclerosis. It also is of interest to determine whether speakers with Parkinson’s Disease and Multiple Sclerosis judged to be nondysarthric via perceptual analyses also demonstrate objective, acoustic profiles of diadochokinesis that are within normal limits. [Work supported by NIH.]

Segmental Timing in Amyotrophic Lateral Sclerosis

This study describes segmental timing patterns for a passage read by speakers with ALS and a group of age- and gender-matched neurologically healthy speakers. Segment durations for ALS speakers' habitual rates (ALS condition) were compared to segment durations for healthy speakers' habitual and slow reading rates (Control Habitual and Control Slow conditions). Temporal differences for pairs of sound classes (i.e., long-short vowels, voiceless-voiced fricatives, voiceless-voiced stop gaps, high-low vowels) and prepausal lengthening of vowels also were studied. The results of the ALS-Control Habitual comparison suggested that the slowed articulatory rate of ALS influences segmental timing for most phonetic events. The finding that local segmental cues for disordered speakers were broadly consistent with their overall (slow) articulatory rate suggests that duration likely does not contribute in a significant way to intelligibility deficits in ALS. A qualitative analysis further indicated that the slowed rate of ALS is not uniformly distributed across phonetic events, but influences segment durations of particular sound categories in ways consistent with the disease process. The analysis comparing segment durations for the ALS and Control Slow conditions suggested that the overall pattern of segmental timing for speakers with ALS was broadly similar to the pattern for voluntarily slowed speech of healthy talkers. Finally, temporal differences for sound classes (i.e., voiceless-voiced fricatives, long-short vowels) and prepausal lengthening for speakers with ALS typically were similar to healthy speakers' habitual and slow speech. There were substantial variability within speaker groups and reversals of expected effects, however. The implication is that temporal differences for sound classes, such as short and long vowels, are not a particularly reliable perceptual cue for listeners.