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PubMed1980

Production and perception of vowel length in spoken sentences.

A series of experiments was conducted to determine (1) the accuracy with which vowel segment durations in spoken sentences can be represented in auditory sensory storage and (2) the extent to which phoneme boundaries in the identification of phonemic vowel length in Dutch are affected by syntactic and/or auditory-phonetic context. In a preliminary production test it was found that durations of both long and short Dutch vowel phonemes in monosyllabic words embedded in sentences are systematically affected by word positions in the sentences. In an initial perceptual experiment, phoneme boundaries and slopes of identification curves were measured for 12 listeners in five different test utterances in a binary forced choice identification test. Perceptual accuracy of vowel duration perception as determined from the slopes of the identification curves corresponds on the average to a just-noticeable difference (JND) of about 5 ms with a test segment duration of about 90 ms. Phoneme boundary values are systematically affected by context in ways predictable from syntactic structure and the auditory-phonetic environment. In a second perceptual experiment it is shown that a major effect on phoneme boundary can be brought about by perceived properties of the test utterance following the monosyllable containing the test segment. In a third perceptual experiment it is shown that the difference between phoneme boundaries in utterance final syllable and in embedded syllable is related to the presence or absence of a perceived speech pause following that syllable. The results of these experiments are interpreted in terms of a simple decision model with a noisy auditory representation of embedded vowel duration, lasting a few hundredths of milliseconds, and a noiseless internal criterion for vowel length identification which is systematically affected by the auditory-phonetic environment.

Adult↗
PubMed1982

Segmental durations in connected speech signals: preliminary results.

The data base, methods for a study of the durations of phonetic units in connected speech, and some preliminary results are described. From readings of two scripts by many talkers, two sets of seven talkers each were selected, based on total reading time, to form a fast group and a slow group of talkers. Using computer graphics and digital playback procedures, the recordings were segmented into breath groups and pauses, and the first four sentences in each script were segmented into phones. The hold and release (that is, plosion and/or frication) portions of stops were identified and measured; less than 50% of the stops included releases. To establish the usefulness of the data base, the first-order statistics of the phonetic segments were determined, and a variety of durational characteristics were compared to existing reports. Analysis of number of breath groups, phonation time, and pause characterized the difference between so-called average fast and average slow talkers; however, no script-independent measure of these variables was found which would accurately predict the classification of individual talkers. The mean durations of various phonetic categories showed essentially the same percentage change when the fast and slow talkers were compared. Preliminary analyses of contextual influences on durations showed some expected changes, and also indicated that certain traditional predictions may not hold for informal connected speech. Gamma functions were fitted to the distributions of durations of various gross categories.

Computers↗
PubMed1983

The role of spectral cues in discrimination of voice onset time differences.

The influence of spectral cues on discrimination peaks in the region of the phonetic voicing boundary was examined. The discriminability of voice onset time (VOT) differences of the same temporal magnitude was assessed using stimuli from labial and velar consonant-vowel VOT continua that differed in the timing of spectral changes associated with the first formant (F1) transition, and in the location of the phonetic boundary. Subjects were initially given labeling tests and fixed-standard AX and all-step discrimination tests on both series. Half the subjects then received all-step discrimination training on one series and half received training on the other series. Finally, all subjects were again given the labeling and discrimination tests on both series. Just noticeable differences (jnds) in VOT were estimated from the all-step functions before and after training. Initial jnds showed that VOT discrimination was most accurate around the voicing boundary on the two continua, where differences in F1 onset frequency accompany variations in VOT. jnds on both series decreased significantly after training, although these regions of greater sensitivity remained. No evidence was seen of increased sensitivity around +/- 20-ms VOT, as expected if auditory processing constraints were influencing temporal order judgments. Comparisons of post-training jnds within and across series indicated that spectral components of VOT, primarily F1 onset frequency differences, exert a substantial influence on discrimination, and, along with other spectral cues provided by source differences at stimulus onset, can account for the discontinuities in discrimination often reported in research with VOT continua. Large phonetic effects also were seen in the initial performance of all subjects: jnds decreased consistently as standards drew nearer the voicing boundary. However, these effects were absent in the final jnds for most subjects. Implications of these findings for the understanding of basic auditory and attentional processes in speech perception are discussed.

Adult↗
PubMed1984

Recognition of speech spectrograms.

The performance of eight naive observers in learning to identify speech spectrograms was studied over a 2-month period. Single tokens from a 50-word phonetically balanced (PB) list were recorded by several talkers and displayed on a Spectraphonics Speech Spectrographic Display system. Identification testing occurred immediately after daily training sessions. After approximately 20 h of training, naive subjects correctly identified the 50 PB words from a single talker over 95% of the time. Generalization tests with the same words were then carried out with different tokens from the original talker, new tokens from another male talker, a female talker, and finally, a synthetic talker. The generalization results for these talkers showed recognition performance at 91%, 76%, 76%, and 48%, respectively. Finally, generalization tests with a novel set of PB words produced by the original talker were also carried out to examine in detail the perceptual strategies and visual features that subjects abstracted from the training set. Our results demonstrate that even without formal training in phonetics or acoustics naive observers can learn to identify visual displays of speech at very high levels of accuracy. Analysis of subjects' performance in a verbal protocol task demonstrated that they rely on salient visual correlates of many phonetic features in speech.

Communication Methods, Total↗
PubMed1984

The detection of French accent by American listeners.

The five experiments presented here examine the ability of listeners to detect a foreign accent. Computer editing techniques were used to isolate progressively shorter excerpts of the English spoken by native speakers of American English and French. Native English-speaking listeners judged the speech samples in one- and two-interval forced-choiced tests. They were able to detect foreign accent equally well when presented with speech edited from phrases read in isolation and produced in a spontaneous story. The listeners accurately identified the French talkers (63%-95% of the time) no matter how short were the speech samples presented: entire phrases (e.g., "two little dogs"), syllables (/tu/ or /ti/), portions of syllables corresponding to the phonetic segments /t/,/i/,/u/, and even just the first 30 ms of "two" (roughly, the release burst of /t/). Both phonetically trained listeners familiar with French-accented English and unsophisticated listeners were able to accurately detect accent. These results suggest that listeners develop very detailed phonetic category prototypes against which to evaluate speech sounds occurring in their native language.

Adult↗
PubMed1988

Auditory/phonetic categorization with the Symbion multichannel cochlear implant.

The phonetic identification ability of an individual (SS) who exhibits the best, or equal to the best, speech understanding of patients using the Symbion four-channel cochlear implant is described. It has been found that SS: (1) can use aspects of signal duration to form categories that are isomorphic with the phonetic categories established by listeners with normal auditory function; (2) can combine temporal and spectral cues in a normal fashion to form categories; (3) can use aspects of fricative noises to form categories that correspond to normal phonetic categories; (4) uses information from both F1 and higher formants in vowel identification; and (5) appears to identify stop consonant place of articulation on the basis of information provided by the center frequency of the burst and by the abruptness of frequency change following signal onset. SS has difficulty identifying stop consonants from the information provided by formant transitions and cannot differentially identify signals that have identical F1's and relatively low-frequency F2's. SS's performance suggests that simple speech processing strategies (filtering of the signal into four bands) and monopolar electrode design are viable options in the design of cochlear prostheses.

Adult↗
PubMed1991

Tempo, stress, and vowel reduction in American English.

Two processes that affect the acoustic characteristics of vowels, namely, phonological and phonetic vowel reduction are discussed. Phonological vowel reduction applies to unstressed vowels. Phonetic vowel reduction is supposed to apply to all vowels and be caused by fast speech rates, context, as well as lack of stress. In this experiment, the effects of changes in stress and in rate of speech (tempo) on the acoustic characteristics of American English monophthongal, nonretroflex vowels were examined. Four male and four female native speakers produced these vowels in two contexts, [h_d] and [b_d], in a carrier sentence, under four conditions of tempo stress (slow-stressed, slow-unstressed, fast-stressed, and fast-unstressed). Measurements of duration and fundamental frequency showed that the subjects did, in fact, vary tempo and stress as instructed. The effect of a change in stress on vowel duration was found to be slightly larger than that of a change in tempo. The putative vowel portion of each utterance was analyzed, formant tracks were obtained, and these were plotted in an auditory-perceptual space [J.D. Miller, J. Acoust. Soc. AM. 85, 2114-2134 (1989)]. These plots served to determine the part of the utterance that could, in most cases, be considered its steady state. For each utterance, an average of the coordinates of this steady-state portion was taken and was used to represent the utterance as a point in the auditory-perceptual space. The distance of these data points from the point representing the acoustic characteristics of a vowel produced by a neutral vocal tract was used to determine the magnitude of phonetic vowel reduction caused by faster tempo and less stress, relative to the slow-stressed condition. Although the results indicate that tempo and stress may not have a major influence on the distances of individual vowels from the neutral point, the size of the vowel space overall was affected. The vowel space was largest for the slow stressed condition and smallest for the fast unstressed condition. In addition, several vowel classifications schemes were tested using linear discriminant analysis, and the one proposed by Miller (1989) performed better than other combinations of fundamental frequency and the first three formants.

Adult↗
PubMed1992

Preliminary results on speaker-dependent variation in the TIMIT database.

A set of phonetic studies based on analysis of the TIMIT speech database is presented. Using a database methodological approach, these studies detail new results in speaker-dependent variation due to sex and dialect region of the talker including effects on stop release frequency, speaking rate, vowel reduction, flapping, and the use of glottal stop. TIMIT was found to be fertile ground for gathering acoustic-phonetic knowledge having relevance to the phonetic classification and recognition goals for which TIMIT was designed, as well as to the linguist attempting to describe regularity and variability in the pronunciation of read English speech.

Databases, Factual↗
PubMed1998

Effects of local speaking rate context on the perception of voice-onset time in initial stop consonants.

This study explored the prediction that local speaking rate context affects the perception of voice-onset time (VOT) in initial stop consonants not only for ambiguous stimuli at the category boundary, but also for good exemplars from the category center [Volaitis and Miller, J. Acoust, Soc. Am. 92, 723-735 (1992)]. Naturally produced exemplars of the voiceless phonetic category were presented in the context of syllables produced at fast or slow speaking rates in a series of perceptual tasks, including phonetic discrimination, identification, and goodness rating. The results from all three tasks revealed no effects of speaking rate context on the perception of VOT in initial stop consonants. Rather, it appears that listeners perceive longer VOTs as better exemplars of the voiceless phonetic category, irrespective of the rate context. Further, an additional condition, in which the instructions and familiarization tasks presented prior to the administration of the perceptual tests were similar to those used by Volaitis and Miller [J. Acoust. Soc. Am. 92, 723-735 (1992)], revealed that the previous results may have been influenced by the experimental design.

Adolescent↗
PubMed1999

Articulatory tradeoffs reduce acoustic variability during American English /r/ production.

The American English phoneme /r/ has long been associated with large amounts of articulatory variability during production. This paper investigates the hypothesis that the articulatory variations used by a speaker to produce /r/ in different contexts exhibit systematic tradeoffs, or articulatory trading relations, that act to maintain a relatively stable acoustic signal despite the large variations in vocal tract shape. Acoustic and articulatory recordings were collected from seven speakers producing /r/ in five phonetic contexts. For every speaker, the different articulator configurations used to produce /r/ in the different phonetic contexts showed systematic tradeoffs, as evidenced by significant correlations between the positions of transducers mounted on the tongue. Analysis of acoustic and articulatory variabilities revealed that these tradeoffs act to reduce acoustic variability, thus allowing relatively large contextual variations in vocal tract shape for /r/ without seriously degrading the primary acoustic cue. Furthermore, some subjects appeared to use completely different articulatory gestures to produce /r/ in different phonetic contexts. When viewed in light of current models of speech movement control, these results appear to favor models that utilize an acoustic or auditory target for each phoneme over models that utilize a vocal tract shape target for each phoneme.

Female↗
PubMed2000

An investigation of current models of second language speech perception: the case of Japanese adults' perception of English consonants.

This study reports the results of two experiments with native speakers of Japanese. In experiment 1, near-monolingual Japanese listeners participated in a cross-language mapping experiment in which they identified English and Japanese consonants in terms of a Japanese category, then rated the identifications for goodness-of-fit to that Japanese category. Experiment 2 used the same set of stimuli in a categorial discrimination test. Three groups of Japanese speakers varying in English-language experience, and one group of native English speakers participated. Contrast pairs composed of two English consonants, two Japanese consonants, and one English and one Japanese consonant were tested. The results indicated that the perceived phonetic distance of second language (L2) consonants from the closest first language (L1) consonant predicted the discrimination of L2 sounds. In addition, this study investigated the role of experience in learning sounds in a second language. Some of the consonant contrasts tested showed evidence of learning (i.e., significantly higher scores for the experienced than the relatively inexperienced Japanese groups). The perceived phonetic distance of L1 and L2 sounds was found to predict learning effects in discrimination of L1 and L2 sounds in some cases. The results are discussed in terms of models of cross-language speech perception and L2 phonetic learning.

Adult↗
PubMed1989

A specialization for speech perception.

The processes that underlie perception of consonants and vowels are specifically phonetic, distinct from those that localize sources and assign auditory qualities to the sound from each source. This specialization, or module, increases the rate of information flow, establishes the parity between sender and receiver that every communication system must have, and provides for the natural development of phonetic structures in the species and in the individual. The phonetic module has certain properties in common with modules that are "closed" (for example, sound localization or echo ranging in bats) and, like other members of this class, is so placed in the architecture of the auditory system as to preempt information that is relevant to its special function. Accordingly, this information is not available to such "open" modules as those for pitch, loudness, and timbre.

Animals↗
PubMed1998

Sensorimotor adaptation in speech production.

Human subjects are known to adapt their motor behavior to a shift of the visual field brought about by wearing prism glasses over their eyes. The analog of this phenomenon was studied in the speech domain. By use of a device that can feed back transformed speech signals in real time, subjects were exposed to phonetically sensible, online perturbations of their own speech patterns. It was found that speakers learn to adjust their production of a vowel to compensate for feedback alterations that change the vowel's perceived phonetic identity; moreover, the effect generalizes across phonetic contexts and to different vowels.

Adaptation, Physiological↗
PubMedDate not supplied

The construction of a first phonology.

Although it is generally accepted that phonological development is grounded in phonetic learning, there is less agreement for the proposition supported here, that the first phonological structuring constitutes a developmental discontinuity. Data from the phonetic and lexical learning of Finnish consonant duration are presented to illustrate the role of (1) child selection of adult words for early context-supported production based on phonetic learning and (2) child adaptation of adult words to an idiosyncratic template for later production as part of an incipient system. We argue that the latter, but not the former, reflects the construction of a first phonology.

Adult↗
PubMedDate not supplied

Acoustic vowel reduction in Creek: effects of distinctive length and position in the word.

Eight speakers (4 male and 4 female) of the Muskogee dialect of Creek pronounced a set of words illustrating the vowels and diphthongs of Creek. These recordings were analyzed acoustically and data on vowel duration and vowel formant frequencies are presented in this paper. The ratio of the durations of dictinctively long and short vowels was 1.8. This ratio showed a sex difference, being larger for female speakers than it was for male speakers. Final lengthening was also observed: both distinctively long and short vowels were longer in word-final position than in word-initial position. The vowel formant data showed two additive, orthogonal phonetic vowel reduction processes: short vowel centralization and positional reduction. Short vowel centralization has been found in many languages. Distinctively long vowels in Creek tended to be more peripheral in the acoustic vowel space than were the distinctively short vowels. Positional reduction is also evident in these data: vowels in word-final position were reduced relative to vowels in word-initial position. Short vowel centralization was preserved in both positions in the word. Positional reduction has been documented in several languages, and these results from Creek lend support to the hypothesis that it is a general property of speech production. The results of this acoustic-phonetic study, the first such study of Creek, are discussed in light of cross-linguistic phonetic trends.

Adult↗
PubMedDate not supplied

Effects of morpheme boundaries on intergestural timing: evidence from Korean.

This paper examines the effects of morpheme boundaries on intergestural timing, and demonstrates that low-level phonetic realization is influenced by morphological structure, i.e. compounding and affixation. It reports two experiments, one using electromagnetic midsagittal articulography (EMA) and one electropalatography (EPG), examining Korean data. The results of the EMA study show that intergestural timing is less variable for adjacent gestures across the word boundary inside a lexicalized compound than inside a nonlexicalized compound, and inside a monomorphemic word than across a morpheme boundary. The EPG study (which examined the timing in palatalization of a coronal) shows that both [ti] and [ni] have more variability in gestural timing when heteromorphemic than when tautomorphemic. Furthermore, the phonetic details of gestural overlap shed light on the asymmetry on palatalization between tautomorphemic and heteromorphemic gestural sequences (e.g. ni vs. n-i), presumably driven by paradigmatic contrast and preference of overlap. In short, what emerges from two experiments is that gestures are coordinated more stably within a single lexical item (a morpheme or a lexicalized compound) than across a boundary between lexical items. In accounting for the stability of intergestural timing within a lexical entry, several hypotheses were discussed including the Phase Window, Bonding Strength, Phonological Timing and Extended Phase Window model newly proposed here. The implication is that the morphological structure may be encoded in the phonetic realization, as is the case with other linguistic structure (e.g. prosodic structure).

Adult↗
PubMedDate not supplied

F0 timing in Kinyarwanda.

In Kinyarwanda (Bantu, Rwanda), a high tone can occur on either the first or the second mora of a syllable. A study of f0 timing in the language was undertaken to determine how such a contrast is realized phonetically, and how this realization is affected by phrase position, word position, and distance from a following high tone. The study also aimed to explore a reported effect of 'tone anticipation' (raising of pitch in a syllable before a high tone) in the language. The study found significant effects of the position of a tone within the syllable, its position within the phrase, and its position with respect to following high tones. Models of f0 timing in Kinyarwanda are proposed, demonstrating the role of moras in phonetic implementation of tone. These models clarify issues regarding the phonological representation of tones in Kinyarwanda, and the division between phonetic patterns and phonological ones.

Humans↗
PubMedDate not supplied

Underlying voicing in Majorcan Catalan word-final stop-liquid clusters.

This study investigates the extent to which phonetic voicing is maintained in word-final clusters composed of an underlying voiced stop followed by nonsyllabic /l/ or /r/ in Majorcan Catalan. Electropalatographic and acoustic data for five speakers of this Catalan dialect reveal that, in agreement with the non-syllabic status of the liquid, voicing for /l/ is only available if occurring during the preceding stop. The rhotic is always phonetically voiceless. Speakers differ regarding the extent to which they keep the underlying stop voicing distinction and the production strategies they use for that purpose. This distinction is highly robust and distributed over the entire syllable in nasal-stop-/l/ clusters for some speakers, but much less clear or absent for those speakers who devoice /l/ as a general rule. Underlying stop voicing is cued primarily by stop closure duration and vocal fold vibration, or else by closure duration rather than by voicing. It may be concluded that the word-final devoicing process operating in Catalan does not apply to Majorcan Catalan tautosyllabic stop clusters with a liquid, and that phonetic voicing may affect just the stop or both the stop and the liquid. The implications of these findings for sound change are discussed.

Cues↗