English Plosives Research Articles

Individual Variation in the Frication of Voiceless Plosives in Australian English: A Study of Twins' Speech

This study is an acoustic–phonetic examination of variation in Australian English consonant production. Group and individual patterns in the rates of frication of the voiceless plosives /p t k/ in Australian English are investigated. Previous studies on voiceless plosive production in Australian English have focussed primarily on /t/, and these analyses have largely been auditory in nature. Further, whereas previous studies have focussed on describing sociophonetic variation within Australian English, this study investigates speaker-specific variation. An analysis of twin speech, produced by young adult male speakers from Melbourne, is presented. The speakers are three identical twin pairs and one non-identical twin pair. The reason for studying twins, and identical twins in particular, is to explore the degree of phonetic difference between pairs of individuals who, theoretically, are as anatomically similar as possible and whose educational levels and home lives have been relatively the same. The speakers were recorded separately, engaging in spontaneous conversation with the first author in two sessions each. All /p t k/ tokens were categorized as fricated or closed using acoustic waveforms and wideband spectrograms. While /t/ was rarely fricated by any speaker, /p/ and /k/ exhibited a wide range of variation in the proportions of tokens fricated, both between speakers, and within twin pairs. Further, each individual's proportions of /p/ and /k/ tokens fricated were relatively consistent across the two recording sessions. Implications of these findings for descriptions of Australian English and theories of speaker characteristics are discussed.

Modeling dialect‐related variability in American English plosives

Socially motivated variation in speech often lies in the differential use of phenomena described in identical or near‐identical terms. This paper investigates the hypothesis that dialect differences may result from the relative distribution of an acoustic characteristic with respect to trading relations with other co‐varying characteristics, or by variations in the characteristic within regions of linguistic stability. Plosive variation among European American and African American English speakers in the upper Midwest is examined. Speakers from both dialect groups may produce plosives instead of interdental fricatives in syllable initial position, and devoice or glottalize apical plosives in syllable final position. Additionally, speakers of both dialects have been observed to hypervoice voiced plosives word‐initially. The current experiment explores the boundary characteristics of a trading relations model within the plosive system of both dialect groups. The specific question addressed by the paper is whether the range of plosive variation suggests a shared property of nonstandard dialects, or whether the relation among acoustic measures is dialect specific. Results are discussed in light of acoustic, perceptual and categorical stability.

Aspiration of Plosives in Māori: Change Over Time*

Māori is the language of the indigenous people of New Zealand. Traditionally the Māori plosive consonants are regarded as unaspirated, in contrast to English voiceless plosives which are strongly aspirated in initial position. This paper traces the increase in aspiration in Māori plosives over time by analysing the Māori and English plosive consonants of three speakers born over a span of nearly 100 years. It shows that both the number of aspirated plosives and the degree of aspiration (measured by VOT) have increased from the oldest speaker (born in 1885) to the youngest speaker (born in 1972) in both languages. There may be some language internal factors at work, but influence from English is a likely cause for this change. The youngest speaker was born before the Māori language revitalization programme was established. The results provide a snapshot of the pronunciation of Māori stops before the development of the kōhanga reo revitalization movement (Māori language nests) in 1982.

Closure Duration and VOT of Word-initial Voiceless Plosives in English in Spontaneous Connected Speech

This is a corpus study on closure duration and VOT in English voiceless stops in word-initial position. 19 speakers’ (10 female, 9 male) data from the Buckeye Speech corpus are used in the study. The first half of the paper introduces a novel approach of automatically finding the point of stop release in large speech database, using Mel spectral templates and similarity scores. The performance and robustness of the algorithm is discussed in detail. To our knowledge, this is also the first automatic measure of closure duration and VOT that is reported in detail in the literature. The second half of the paper studies the closure duration and VOT as calculated by the procedure described in the first half, and investigate the correlation between these durations and a number of linguistic and extra-linguistic factors.

Speech across the menstrual cycle: A replication and extension study

Whiteside et al. [S.P. Whiteside, A. Hanson, P.E. Cowell, Hormones and temporal components of speech: sex differences and effects of menstrual cyclicity on speech, Neurosci. Lett. 367 (2004) 44–47] documented effects of menstrual cycle phase and sex on voice onset time (VOT) in naturally timed speech using whole words. VOT is a temporal component of speech that plays an important role in production and perception [L.L. Koenig, Laryngeal factors in voiceless consonant production in men, women, and 5-year-olds, J. Speech Lang. Hear. Res. 43 (2000) 1211–1228; A. Löfqvist, L.L. Koenig, R.S. McGowan, Vocal tract aerodynamics in /aCa/ utterances: measurements, Speech Commun. 16 (1995) 49–66; T.M. Nearey, B. Rochet, Effects of place of articulation and vowel context in VOT production and perception for French and English Stops, J. Int. Phon. Assoc. 24 (1994) 1–18; L.M. Rimol, T. Eichele, K. Hugdahl, The effect of voice-onset-time on dichotic listening with consonant–vowel syllables, Neuropsychologia 44 (2006) 191–196; P.G. Simos, R.L. Diehl, J.I. Breier, M.R. Molis, G. Zouridakis, A.C. Papanicolaou, MEG correlates of categorical perception of a voice onset time continuum in humans, Cogn. Brain Res. 7 (1998) 215–219; S.P. Whiteside, J. Marshall, Developmental trends in voice onset time: some evidence for sex differences, Phonetica 58 (2001) 196–210]. The present study was designed to replicate and expand upon Whiteside et al. [S.P. Whiteside, A. Hanson, P.E. Cowell, Hormones and temporal components of speech: sex differences and effects of menstrual cyclicity on speech, Neurosci. Lett. 367 (2004) 44–47] using a speeded syllable repetition paradigm. VOT measurements for 6 English plosives (/p b t d k g/) were obtained from speech samples of 15 women and 20 men (age 20–25 years). Women were tested across two points in the menstrual cycle (Days 2–5: low estrogen and progesterone/low-EP; Days 18–25: high estrogen and progesterone/high-EP) and men were tested once. Results indicated significant interaction between menstrual cycle phase and voicing ( F(1,14) = 8.239, P < 0.02), whereby the voiced plosives (b, g) displayed shorter VOT values and the voiceless plosives (p, k) displayed longer values at the high-EP phase. Thus, the distinction between the voiced and voiceless plosive was enhanced at high-EP. Significant sex effects ( F(1,33) = 10.080, P < 0.005) were seen with women at high-EP but not the low-EP phase having longer VOT values than men for voiceless plosives. Sex differences between the voiced and voiceless plosives were enhanced at the high-EP phase. This study indicates a role for activational ovarian hormones in regulating temporal features of speech in both whole words and speeded syllable repetition.

Control of Voice-Onset Time in the Absence of Hearing

The relation between partial or absent hearing and control of the voicing contrast has long been of interest to investigators, in part because speakers who are born deaf characteristically have great difficulty mastering the contrast and in part for the light it can cast on the role of hearing in the acquisition and maintenance of phonological contrasts in general. One of the phonetic characteristics that distinguish voiced from voiceless plosives in English (p/b, t/d, k/g) is voice onset time (VOT): the interval from plosive release to the onset of voicing of the following vowel. This article first reviews research on VOT anomalies in the speech production of prelingually and postlingually deaf speakers. Then it turns to studies of the mechanisms in speech breathing, phonation and articulation that underlie those anomalies. In both populations of speakers, there is a tendency for the difference between voiced and voiceless VOT to be reduced, to the point for many speakers that there is in effect a substitution of the voiced for the voiceless cognate. The separation of the cognate VOTs can be enhanced when some hearing is restored with a cochlear implant. Both populations also present anomalies in speech breathing that can hinder the development of intraoral pressures and transglottal pressure drops that are required for the production of the VOT contrast. Its successful management further requires critical timing among phonatory and articulatory gestures, most of which are not visible, rendering the VOT contrast a particular challenge in the absence of hearing.

Haptic-auditory interference from air flow in speech perception

Previous work on haptic interference in auditory perception has shown McGurk-like effects from manual-tactile contact with the face [Fowler and Dekle, JEP:HPP 17, 816–828 (1991)]. The present study investigates whether indirect haptic input affects auditory perception. A novel method was developed in which one experimenter blew puffs of air onto a subject’s neck while another produced English plosives, creating possible mismatches between the sensation of aspiration and its acoustic presence. Subjects were blindfolded and wore headphones playing white noise. For 50% of the trial, one experimenter, whose presence was hidden from the subjects, blew puffs of air on subjects’ necks lightly enough to be perceived but not noticeable as unnatural. Simultaneously, a second experimenter produced syllables with bilabial plosive onsets (aspirated /p/ or unaspirated /b/) and subjects were asked to repeat what was heard. Sessions were videotaped and three observers rated successful simultaneity of stimuli. Results indicate cross-modal interference. Subjects showed higher accuracy of speech perception when appropriate haptic stimuli accompanied the auditory stimuli. Moreover, when presented with mismatched tactile and auditory stimuli, subjects demonstrated the fusion of the two modes. Subjects perceived /pa/ when auditory stimulus /ba/ was presented with emulating aspiration. [Work supported by NSERC.]

Hormones and temporal components of speech: sex differences and effects of menstrual cyclicity on speech

Voice onset time (VOT) is a salient acoustic parameter of speech which signals the ‘voiced’ and ‘voiceless’ status of plosives in English (e.g. the initial sound in ‘bat’ versus the initial sound in ‘pat’). As a micro-temporal acoustic parameter, VOT may be sensitive to changes in hormones which may affect the neuromuscular systems involved in speech production. This study adopted a novel approach by investigating the effects of menstrual cycle phase and sex on VOT. VOT data representing the six plosives of English (/p b t d k g/) were examined for seven women (age 20–23 years) at two phases of the menstrual cycle (day 18–25: high estrogen and progesterone; day 2–5: low estrogen and progesterone). Results indicated that menstrual cycle phase had a significant interaction with the identity of the plosive ( F (5,30) = 5.869, P < 0.002). Menstrual cycle phase also had significant effects on the contrasts between cognate voiced and voiceless plosives ( F (1,6) = 11.444, P < 0.02); samples from the high hormone phase displayed an enhanced voiced/voiceless contrast. Subsequently, VOT data samples from the two phases of the menstrual cycle were compared with those from five men in order to explore sex differences at different phases of the menstrual cycle. Low hormone phase samples displayed no significant sex differences for either VOT values ( F (1,10) = 2.085, P > 0.05), or the contrast between voiced and voiceless cognates ( F (1,10) = 0.407, P > 0.05). In contrast, the high hormone phase VOT samples displayed significant plosive by sex interactions ( F (5,50) = 4.442, P < 0.005). In addition, significant sex differences were found for the contrasts between cognate voiced and voiceless plosives ( F (1,10) = 5.019, P < 0.05); the women displayed a more marked voiced/voiceless contrast. The findings suggest that ovarian hormones play some role in shaping some temporal components of speech.

Speakers' sex differences in voice onset time: some preliminary findings.

This study presents a brief investigation into sex differences of speakers in the voice onset time of English plosives that are stressed in both word-initial and prevocalic position. 72 short phrases were presented to 5 men (range 25 to 37 years, mean age 34.2 yr.) and five women speakers (range 28 to 38 years, mean 32.6 yr.). Analysis showed that the women as speakers had on average, longer voice onset time values than their male peers.

Changes in voice-onset time in speakers with cochlear implants.

Voice-onset time (VOT) and syllable duration were measured for the English plosives in /Cad/(C = consonant) context spoken by four postlingually deafened recipients of multichannel (Ineraid) cochlear implants. Recordings were made of their speech before, and at intervals following, activation of the speech processors of their implants. Three patients reduced mean syllable duration following activation. Using measures of VOT and syllable duration from speakers with normal hearing [Volaitis and Miller, J. Acoust. Soc. Am. 92, 723-735 (1992)] and from the subjects of this study, VOT is shown to vary approximately linearly with syllable duration over the ranges produced here. Therefore, the VOT of each token was adjusted for the change in syllable duration of that token relative to the mean syllable duration in the first baseline session. This variable, labeled VOTc, was used to evaluate the effects on voicing of the speakers' renewed access to the voicing contrast provided by their implants. Preimplant, all four speakers characteristically uttered voiced plosives with too-short VOT, compared to the measures for hearing speakers. Voiceless plosive mean VOT was also abnormally short for two of the speakers, and close to normal for the remaining two. With some hearing restored, subjects made relatively few errors with respect to voicing when identifying plosives in listening tests, and three of the four speakers lengthened VOTc. The findings are interpreted as supporting the hypothesis that speakers use their hearing to calibrate mechanisms of speech production by monitoring the relations between their articulations and their acoustic output.

Changes in voice-onset time in speakers with cochlear implants

Voice-onset time (VOT) was measured for the English plosives in /Copen aye/ context spoken by three female and one male postlingually deafened recipients of multi-channel (Ineraid) cochlear implants. Recordings were made of their speech before activation of their speech processors and at intervals after activation, extending over several years. Also measured were: instantaneous oral airflow; sound pressure level; an indirect index of glottal aperture; and average airflow during passage readings. Pre-implant, all four speakers characteristically uttered plosives with too-short VOT, compared to normative data. After activation of their processors, all four were relatively accurate in identifying plosives with respect to voicing, and the three female speakers lengthened VOT. The women also increased glottal aperture post-activation. However, none of the women increased peak oral flow following plosive release, possibly because of a countervailing decrease in subglottal pressure: all three reduced SPL post-activation. Complementary results were found for the male speaker: a decrease in inferred glottal aperture and an increase in oral flow accompanied by an increase in SPL. Increases in glottal aperture are expected to inhibit the onset of voicing in the plosives [K. Stevens, Phonetica 34, 264–279 (1977)]. Consequently, some or all of the observed increases in VOT with activation of the implant processors may be due to ‘‘postural’’ adjustments of the larynx. [Work supported by N.I.D.C.D.]

The Dominant Role of English Plosives in Connected Speech Through a Contrastive Analysis

The Dominant Role of English Plosives in Connected Speech Through a Contrastive Analysis

Voice onset time and F0 perturbation under conditions of mixed airstream mechanism

Pulmonic and velaric airstream mechanisms are employed together in the production of clicks and accompanying vowels. Questions thus emerge as to the temporal and microprosodic coordination of these two mechanisms, particularly with respect to the phonatory characteristics of clicks. This report is on the acoustic measurement of the post‐alveolar click in Sesotho, with particular reference to VOT and F0 perturbations. There are two phonemically distinct varieties of click in Sesotho, which might be characterized as aspirated and unaspirated in accordance with orthographic conventions. The unaspirated click has a mean VOT of approximately 40 ms on the order of voiceless aspirated plosives in English. The aspirated click has a mean VOT of approximately 120 ms, greater than any plosive type reported by Lisker and Abramson [Language 47, 767–785 (1971)]. The F0 values were measured pre‐ and post‐click in both word‐initial and word‐medial clicks. Our data indicate a consistent fall in F0 immediately prior to a c...

Multiple features analysis of intervocalic English plosives.

A controlled study involving a multi-feature acoustic analysis of intervocalic English plosives has been conducted for the purpose of evaluating acoustic stop features for automatic stop recognition. Both time-domain and frequency-domain features were measured via computer interaction. The resulting discrete density functions allowed for a comparative evaluation of individual (and in some instance conditional or combined) feature contributions to stop identification. This evaluation consisted of the maximum a posteriori probability of a correct identification of either the voicing mode (voiced or voiceless) or the place of articulation (labial, alveolar, or palato-velar) of a stop independent of the talker or of a limited phonetic context. These features included variations on ten acoustic features for voicing mode identification and seven for place-of-articulation identification. The data base for this study consisted of five male and five female talkers producing all permutations of the stops C epsilon /p,t,k,b,d,g/ and vowels V epsilon /i,e,a,u/ in the sentence frame "please say /h 'CVt/ again." While the results indicate that the acoustic features of burst/formant-onset frequency and voice onset time (VOT) are the two single most salient features for stop identification, several additional features are also shown to provide important redundancy for identification. The often overlooked time-domain features of "double-burst release" and "voicing during stop closure" were found to be particularly useful in providing such redundancy.

Laryngeal-oral coarticulation in glottalized English plosives

It has been observed by many writers on English phonetics that /p/, /t/, /k/ and /tʃ/ are frequently glottalized, i.e. produced with closed glottis. This observation raises a variety of interesting questions. Firstly, the phonological environments in which glottalization occurs have yet to be satisfactorily described; a preliminary attempt at a re-statement was made in Roach (1973) and a fuller account presented in Roach (1978). Secondly, it is of interest to study the articulatory mechanisms used in the production of glottalization, both from the point of view of finding out more about how laryngeal closures in speech are produced, and also with respect to the temporal organization of the laryngeal and supralaryngeal closures. Thirdly, since the incidence of glottalization (and of the closely related phenomenon of glottal replacement) appears to vary according to geographical and social factors, age and sex, it is of interest in dialectological and sociolinguistic studies of English. Finally, in a wider context, glottalization may be studied as being potentially an on-going sound change in English, and as a phenomenon that might possibly be linked with similar laryngeal articulations in other languages, e.g. the stød of Standard Danish and of West Jutland Danish.

Aerodynamics of stops in continuous speech

Simultaneous intraoral air pressure and acoustic recordings were collected from three adult males during a spontaneous monologue and citation logoteme speaking tasks. Peak intraoral air pressure ( P 0 ), duration of consonantal closure ( D c ) and peak r.m.s. sound pressure associated with the consonantal release ( P b ) for selected English plosives were obtained from the recordings. Systematic changes in aerodynamic parameters associated with a conversational context vs citation contexts were probed. Intraoral pressures were found to be comparable to published values for plosives in syllable- and sentence-contexts, and voiceless plosives were consistently produced with greater magnitudes of P 0 than were voiced plosives. The data also indicate weak to moderate correspondences among P 0 , D c and P b , show that contextual and idiosyncratic effects significantly modify aerodynamic parameters of stop consonant articulation.

Voice onset time, frication, and aspiration in word-initial consonant clusters.

The voice onset time (VOT) and the duration of the burst of frication noise at the release of a plosive consonant were measured from spectrograms of word-initial consonant clusters. Mean data from three speakers reading English words in a sentence frame indicated that the VOT changed as a function of the place of articulation of the plosive and as a function of the identity of the following vowel or sonorant consonant. Burst durations varied in a similar way such that the remaining interval of aspiration in /p, t, k/ was nearly the same duration in comparable phonetic environments. The VOT was longer before sonorants and high vowels than before mid- and low vowels. Aspiration was also seen in an /s/-sonorant cluster. To explain these regularities, production strategies and perceptual cues to a voicing decision for English plosives are considered. Variations in VOT are explained in terms of articulatory mechanisms, perceptual constraints, and phonological rules. Some VOT data obtained from a connected discourse were also analyzed and organized into a set of rules for predicting voice onset time in any sentence context.

Role of formant transitions in the voiced-voiceless distinction for stops.

Previous research on acoustic cues responsible for the voiced-voiceless distinction in prestressed English plosives has emphasized the importance of voicing onset time with respect to plosive release (VOT). Voiced plosives in English normally have a short VOT (less than 20–30 msec) and a significant formant transition is present following voice onset. Voiceless plosives in prestressed position, on the other hand, have relatively long VOT's (greater than about 50 msec) and the formant transitions are essentially completed prior to voice onset. Our experiments with synthetic speech compare the role of VOT and the presence or absence of a significant formant transition following voicing onset as cues for the voiced-voiceless distinction. The data indicate that there is a significant trading relationship between these two cues. The presence or absence of a rapid spectral change following voice onset produces up to 15-msec change in the location of the perceived phoneme boundary as measured in terms of absolute VOT. One can speculate that the auditory system may be predisposed to detect the presence or absence of a rapid spectrum change as a general property of acoustic inputs. If this is the case, then the acquisition of the voiced-voiceless distinction in infants may be conditioned initially by the presence or absence of this property at the onset of voicing rather than by absolute VOT.

The problem of unstressed vowels and the coarticulation within consonantal clusters for English

In his book An Introduction to the Pronunciation of English A. C. Gimson (1970) describes the articulation of the English plosives in different phonetic contexts. He demonstrates here (146–54 and 156–8) and elsewhere (Gimson, 1960) the articulatory instability of, in particular, the alveolar plosives /t/ and /d/ in English. As W. S. Allen (1960) points out, the predominance of instability associated with the alveolar plosives, rather than with the bilabials /p/ and /b/ or velars /k/ and /g/ may correlate with the more common occurrence of the alveolars rather than with articulatory or other kinds of constraints specific to consonantal clusters containing /t/ and /d/.

On The Perception of Unreleased Voiceless Plosives in English

An experiment concerned with the possibility of distinguishing auditively between unreleased /?/ and unreleased /p/, /t/, and /k/ in English was carried out, with two groups of hearers, one listening by means of earphones, one listening by means of loudspeaker. It was found that correct identification of all the voiceless stops largely depended on the way in which the sounds were (re)produced and conveyed to the hearers. It was also found that correct identification very much depended on the quality of the preceding vowel sound, especially in the case of /p/, /k/, and /?/. Under the best listening conditions /?/ was identified with considerable accuracy. Under less favourable conditions the identification was—in part—scarcely better than pure chance.