Stop Clusters Research Articles

Aspirates: Their development and depression in Ikalanga

This paper looks at the development of aspiration in Ikalanga (Kalanga) stops, a Bantu language of the Shona group classified in Guthrie as S. 16. As in many other languages, Ikalanga has phonemic aspiration. As a result, it makes a three-way contrast between voiceless non-aspirated stops, voiceless aspirated stops, and voiced stops. Aspiration in some of the Ikalanga stops developed from two factors : (i) the influence of the super close vowels of Proto-Bantu on the preceding voiceless stop and (ii) a nasal plus stop sequence in Proto-Bantu. Aspirated stops from a nasal+stop cluster are phonetically and phonologically distinct from other aspirated stops in that, in their interaction with High tones, they behave like depressor consonants. Thus, Ikalanga is shown to have two sets of depressor consonants: voiced obstruents, and breathy voice aspirates derived from Proto-Bantu nasal plus stop clusters.

The relative weighting of acoustic properties in the perception of [s] + stop clusters by children and adults.

We examined the perceptual weighting by children and adults of the acoustic properties specifying complete closure of the vocal tract following a syllable-initial [s]. Experiment 1 was a novel manipulation of previously examined acoustic properties (duration of a silent gap and first formant transition) and showed that children weight the first formant transition more than adults. Experiment 2, an acoustic analysis of naturally produced say and stay, revealed that, contrary to expectations, a burst can be present in stay and that first formant transitions do not necessarily distinguish say and stay in natural tokens. Experiment 3 manipulated natural speech portions to create stimuli that varied primarily in the duration of the silent gap and in the presence or absence of a stop burst, and showed that children weight these stop bursts less than adults. Taken together, the perception experiments support claims that children integrate multiple acoustic properties as adults do, but that they weight dynamic properties of the signal more than adults and weight static properties less.

Integration of acoustic information in the perception of [s] ± stop clusters by children and adults

To compare the integration of acoustic information in phonetic perception by young children and adults, second formant frequency at voicing onset (F2 onset) and gap duration were varied as cues distinguishing ‘‘spa’’ and ‘‘sa.’’ Listeners performed same–different (AX) discrimination in four conditions. The gap of the standard (A) stimulus was always consistent with ‘‘spa;’’ gaps of the comparison (X) stimuli decreased in duration along a continuum, thus becoming more consistent with ‘‘sa.’’ In the two ‘‘one-cue’’ conditions, F2 onset was the same for the A and X stimuli. In the ‘‘two-cue cooperating’’ condition, F2 onset for stimulus A supported ‘‘spa,’’ and F2 onset for X stimuli supported ‘‘sa.’’ In the ‘‘two-cue conflicting’’ condition, F2 onset for stimulus A supported ‘‘sa,’’ and F2 onset for X stimuli supported ‘‘spa.’’ Results led to three conclusions: (1) Child and adult discrimination performance was similar overall, suggesting that the child-adult differences across conditions were not due to differences in general auditory ability. (2) The acoustic cues were integrated in phonetic perception, but acoustic differences were nonetheless accessible perceptually for AX discrimination. (3) However, these acoustic differences are less accessible to adults than to children after integration in phonetic perception. [Work supported by research Grant No. 5 RO1 DC 00633 from the NIDCD/NIH.]

Realizations of consonant clusters by children with phonological impairment

Children with phonological impairment frequently have difficulty producing consonant clusters. Speech pathologists often use phonological processes to describe children's productions of consonant clusters, a commonly used description being cluster reduction. However, this description does not adequately address children's differing realizations of consonant clusters. The purpose of this paper is to develop and refine methods for the characterization of realizations of consonant clusters. The work of Greenlee (1974) and Chin and Dinnsen (1992) has been extended by examining the effect of syllable position, number of elements and constituents on children's realizations of consonant clusters. Specifically, word-initial fricative clusters, stop clusters, three element fricative + stop clusters, and word-final nasal clusters and fricative + stop clusters were examined. The results for 40 phonologically impaired children between the ages of 3;6 and 5;0 years are compared with those of Chin and Dinnsen (1992). The relationships found between child and adult representations of clusters suggest the importance of considering syllable position, number of elements and the constituents of consonant clusters when analysing phonologically impaired children's speech sounds.

Cross-modal context effects on the perception of /r/ and /l/ in a speech and nonspeech mode

Norrix and Green [J. Acoust. Soc. Am. 99, 2591–2592 (1996)] provided evidence for cross-modal context effects on the perception of /r/ and /l/ in a stop cluster. Tokens from a synthetic /iri–ili/ continuum were dubbed onto a visual /ibi/. When presented in an auditory-visual (AV) condition, the tokens were perceived as ranging from /ibri/ to /ibli/. Results indicated a reliable shift in the AV condition relative to an auditory-only (AO) condition. This shift was in accord with acoustic consequences of articulating /r/ and /l/ in a stop cluster. In the current study, sine-wave analogs of the /iri–ili/ tokens were constructed and presented to two groups of observers in an AO and AV condition. Group One was told they would hear schematic speech sounds and instructed to identify what they heard as /r/ or /l/. Group Two made up their own criteria for classifying the tokens as nonspeech sounds. Results indicated a reliable shift in the /r–l/ boundary between the AO and AV conditions for the speech group only and suggest that the influence of the visual articulatory context depends upon listeners interpreting the auditory tokens as speech. [Work supported by NIDCD, NIH.]

Temporal effects on successive consonants in Swedish

The duration of phonetic components in a syllable is known to be affected by the syllable’s relative prominence, along with the number and articulatory nature of phonological segments in a word. This study addresses the durational effect of these factors on successive segments in Swedish consonant clusters. Ten native Swedish speakers were recorded producing monosyllabic and disyllabic target words which were either focused or not focused in a carrier phrase. Each word contained an /s/+stop cluster or stop+/s/ cluster in which the stop was /p,t/ or /k/. The durations of the /s/ frication and stop closure were measured. Results indicate that focus consistently increases the duration of a cluster and its constituents. In addition, little difference in closure duration was observed among /p,t,k/. Within disyllabic words, the cluster’s first segment, whether a stop or an /s/, was systematically longer than the second segment in both nonfocal and focal conditions. The reverse tendency was found for monosyllabic words; the cluster’s second segment was generally longer than the first segment in the focal condition, and no difference due to position in the cluster was observed for the nonfocal condition. These results are discussed in terms of the relative timing of successive consonants within clusters.

Auditory‐visual context effects on the perception of /r/ and /l/ in a stop cluster.

Context effects in speech perception are thought to reflect knowledge about coarticulatory influences from the surrounding phonetic environment. This study investigated if such effects occur when the context is specified in the visual modality and segmental information in the auditory modality. In the first experiment, two continua were synthesized: one varying from /iri–ili/ and the other from /ibri–ibli/. When presented to listeners for identification as /r/ or /l/, there was a significant shift in the category boundary between the two continua. In a second experiment, the /iri–ili/ tokens were paired with visual tokens of a talker saying /ibi/. When presented in an auditory‐visual (AV) condition, these tokens were perceived as ranging from /ibri/ to /ibli/. Observers also identified the /iri–ili/ tokens in a separate auditory‐only (AO) condition. Results indicated a similar shift in the /r–l/ boundary between the AO and AV conditions. Analysis of /r/ and /l/ productions revealed that the perceptual adjustments were consistent with the acoustic consequences of articulating /r/ and /l/ in a stop cluster. The findings suggest that the perceptual adjustment reflects cross‐modal knowledge of the coarticulatory effects of a bilabial consonant on the acoustic realization of /r/ and /l/. [Work supported by NIDCD, NIH.]

Nhanda Glottal Stop

Nhanda is unique among the Pama-Nyungan languages of Western Australia in exhibiting a distinctive glottal stop. This paper describes the position of glottal stop within Nhanda phonology and morphology, and proposes two distinct historical origins for the glottal stop. In one case, glottal stop is the reflex of intervocalic glides *y and *w; in the other, it derives from *w {a,)R sequences, resulting in rhotic-glottal stop clusters.

Durational analysis of stridency errors in children with phonological impairment

This study investigated children's knowledge, evidenced acoustically, of contrasts involving stridents as related to treatment progress. Durational measures (VOT) were used to examine possible acoustic markers of /s/ + stop clusters vs. stop singleton contrasts and initial fricative vs. stop contrasts in six pre-school children with phonological impairment. Other aspects of the children's phonological knowledge were examined for their correspondence to acoustic findings and to treatment progress. One of three stopping subjects produced a durational acoustic distinction between stop and fricative targets prior to treatment. This subject, who also had more knowledge of the fricative class, required the shortest treatment period to establish a contrast between initial stops and fricatives in comparison to two subjects who had less knowledge of fricatives and no acoustic distinction. All three cluster subjects produced long lag VOTs in stops that replaced /s/ + stop clusters; one of these children displayed a weak signilicant difference in VOT means for is/ + stop cluster and singleton targets, but was not the subject with the lowest number of treatment sessions. Results are discussed in reference to the utility of acoustic measures and the convergence of those measures with other sources of knowledge as it relates to treatment outcomes.

An electropalatographic study of stop consonant clusters

This is an electropalatographic investigation of coarticulation for heterosyllabic stop consonant clusters in American English and Catalan VCCV sequences. The heterorganic clusters under analysis were [tk], [kt], [tp], [pt], [kp], [pk]. Evidence for gestural overlap between the two adjacent consonants in the cluster is found quite systematically about the closure midpoint and, less so, at C1 onset and at C2 offset. Overlap occurs between constrained and unconstrained lingual regions (e.g., [p] is produced with more alveolar contact than usual when preceded by [t]) and gives rise to blending between tongue front and tongue dorsum activity during the production of lingual clusters [kt] and [tk]. Clusters are equally sensitive to vowel-dependent effects at all moments in time during the closure period. Such effects are quite large for clusters involving lingual [t] or [k] and non-lingual [p] and quite small for clusters made of the two former lingual stop consonants. These data on consonant- and vowel-dependent coarticulatory effects suggest that stop clusters are produced as highly cohesive production units. A constraint for anticipatory vowel-dependent effects to occur at the cluster midpoint but not so at cluster onset can be taken in support of a time-locked model of coarticulation. Speaker-dependent trends were also observed.

Influences of contextual and local temporal information on perception of a stop consonant after [s

Much of the perceptual information for a stop consonant in an [s]-stop cluster inheres in temporal properties of the acoustic signal local to the period of low energy corresponding to stop closure. However, stop percepts in this context are also influenced by the rate of speech in a precursor phrase to which the cluster is appended. The two experiments in this paper attempt to explore the dissociability of these local and longer-term perceptual influences, and to investigate the interactions between them. The results of the experiments reveal a complex pattern of interactions which suggests that a simple distinction between segmental and suprasegmental temporal information for phonetic contrasts is unrealistic.

Towards an articulatory phonology

ABSTRACTWe propose an approach to phonological representation based on describing an utterance as an organised pattern of overlapping articulatory gestures. Because movement is inherent in our definition of gestures, these gestural ‘constellations’ can account for both spatial and temporal properties of speech in a relatively simple way. At the same time, taken as phonological representations, such gestural analyses offer many of the same advantages provided by recent nonlinear phonological theories, and we give examples of how gestural analyses simplify the description of such ‘complex segments’ as /s/–stop clusters and prenasalised stops. Thus, gestural structures can be seen as providing a principled link between phonological and physical description.

Further experiments in the perception of French plosives.

The present paper is a continuation of a previous study, in which several cues in French stop consonant perception were investigated. In a first series of experiments, identification of a stop as fortis versus lenis turned out to be influenced by whether the following consonant was a fricative or a plosive. Taking the results of this first series as a point of departure, the next experiment focussed on the possible masking influence of friction noise on the perception of a preceding stop. This hypothesis, however, was not confirmed by the outcome of the experiment. Two further experiments showed that periodicity in a stop plus stop cluster is assigned to the first or the second stop, depending on its position in the cluster, even when the first stop is not released. The general discussion places the results within a general frame of consonant perception in French.

Simplification of /s/ + stop consonant clusters: a developmental perspective.

This longitudinal study examined individual patterns and changes in /s/ + stop cluster simplifications of six normally developing children. Subjects produced selected words containing initial voiced and voiceless stops and /s/ + stop clusters at monthly intervals. Speech samples were transcribed phonetically, and voice onset times (VOT) of the stop consonants were measured. The results revealed that subjects reduced clusters most frequently to stop consonants with short-lag VOTs. However, two children also occasionally employed prevoicing, and one subject used long-lag VOTs in cluster-reduced stops. Because cluster-reduced stops and voiced singleton stops were generally produced with similar VOTs, it was concluded that subjects represented clustered stops most frequently as phonemically voiced.

The role of release bursts in the perception of [s]-stop clusters.

The role of the release burst as a cue to the perception of stop consonants following [s] was investigated in a series of studies. Experiment 1 demonstrated that silent closure duration and burst duration can be traded as cues for the "say"-"stay" distinction. Experiment 2 revealed a similar trading relation between closure duration and burst amplitude. Experiments 3 and 4 suggested, perhaps surprisingly, that absolute, not relative, burst amplitude is important. Experiment 5 demonstrated that listener's sensitivity to bursts in a labeling task is at least equal to their sensitivity in a burst detection task. Experiments 6 and 7 replicated the trading relation between closure duration and burst amplitude for labial stops in the "slit"-"split" and "slash"-"splash" distinctions, although burst amplification, in contrast to attenuation, had no effect. All experiments revealed that listeners are remarkably sensitive to the presence of even very weak release bursts.

A longitudinal study of the development of stop consonant production in normal and Down's syndrome children.

In order to compare phonological development in normal and Down's syndrome children, longitudinal observations were made of four normal children from 18 to 36 months of age and five Down's syndrome children from 3 to 6 years of age. Singleton stops and stop clusters were analyzed to determine if the Down's syndrome children evidenced phonological processes and other sound patterns similar to those of the normal children. Although quite similar patterns were observed for the two groups, the Down's syndrome children showed considerable delay in comparison to the normally developing children.

Temporal characteristics of "functionally" misarticulated /s/ in 4- to 6-year-old children.

This paper reviews instrumental studies of "functional" misarticulations in children and reports an experiment involving acoustic measures of the duration of normally articulated and misarticulated /s/. Three subject groups (n = 7 in each group) included normally articulating adults, normally articulating children, and children who misarticulate the /s/ sound. Multiple repetitions of nonsense sequences containing /s/ were obtained from each subject, and group and individual subject comparisons were based on means, standard deviations, and the derived coefficient of variation associated with /s/ duration. Results indicate that /s/ durations of misarticulating children are significantly more variable than those of normally articulating children, and that this difference is more striking in /s/-stop clusters than in the case of singleton /s/. The possibility is raised that the variability differences between the two child groups may reflect differences in speech motor control capabilities. It is suggested that such control differences should predict temporal variability differences between the two child groups for sounds which are articulated correctly by children in both groups. In addition, these variability differences should be observed for the spectral dimension of speech sound production, since this measure is sensitive to control of articulatory configuration.

A note concerning /s/ plus stop clusters in the speech of language-delayed children

ABSTRACTThe acquisition of /s/ plus stop clusters by language-delayed children was compared with normal acquisition, first, for phonemic substitutions and second, for differential use of voice onset time (VOT) for the substituted stops. Ten children, diagnosed as language delayed, produced 95 percent of the intended clusters as singleton stops; children who could employ VOT contrastively produced most stops, substituting for clusters with VOT values in the long lag range.

/s/ plus stop clusters in children's speech.

Young children frequently substitute stops for fricative-stop clusters. In this paper, we report acoustic measurements for children's intended voiced and voiceless stops, and for stops substituting for clusters. Judging from voice-onset time measurements, children employ various strategies for assigning phonological status to the substituted stops.

/s/ + stop clusters in the speech of ten language-delayed children

In the acquisition of /s/ + stop clusters, before correct production, children commonly substitute one of the members for the entire cluster, the most common substitute being a stop at the appropriate point of articulation. Furthermore, there is tentative evidence that some children attempt to distinguish the stops substituting for clusters from voiced stops. The purpose of this investigation was to compare the acquisition of /s/ + stop clusters by language-delayed children to normal acquisition, first, in terms of phonemic substitutions and, second, in terms of differential use of VOT for the substituted stops. Ten children diagnosed as language-delayed served as subjects, C.A. 3;0 to 8;7; all used language below expectation for their chronological age. Each child recorded three tokens of near minimal triplets, beginning with a voiced stop, a voiceless stop and an /s/ + stop cluster, (e.g., Kate, gate, skate), for all three points of articulation, bilabial, alveolar, and velar in the course of identifying pictures. The children produced 95% of the intended clusters as singleton stops. VOT measurements for all stops were made from spectrograms. If the criterion for appropriate use of VOT to distinguish voiced from voiceless stops is taken to be +30 ms, then six of the ten children were producing voiceless and voiced stops appropriately over 80% of the time. For these children, 86% of the stops substituting for clusters were produced with VOT values in the long lag range. The other four children employed a unimodal VOT distribution for all types of stops, voiceless, voiced, and substituting for clusters. The data suggest that language delayed and normal children follow similar strategies in the acquisition of /s/ + stop clusters.