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PubMed1989

Acoustic-phonetic characteristics of speech produced in noise and while wearing an oxygen mask.

The present study investigated changes in the prosodic and acoustic-phonetic features of isolated words by four male talkers speaking in quite and in pink noise at a level of 95 dB SPL. Speech samples were collected both with and without an oxygen mask. Changes in duration, fundamental frequency, total energy, and formant center frequency were analyzed. In addition to the expected changes of increased pitch and amplitude associated with speaking in noise without an oxygen mask, significant effects were found (particularly in the formant center frequencies) as a result of using the oxygen mask. When the oxygen mask was employed, no further significant changes were caused by adding noise to the speaking situation.

Humans↗
PubMed1989

Perceptual differences between vowels located in a limited phonetic space.

The perception of subphonemic differences between vowels was investigated using multidimensional scaling techniques. Three experiments were conducted with natural-sounding synthetic stimuli generated by linear predictive coding (LPC) formant synthesizers. In the first experiment, vowel sets near the pairs (i-I), (epsilon-ae), or (u-U) were synthesized containing 11 vowels each. Listeners judged the dissimilarities between all pairs of vowels within a set several times. These perceptual differences were mapped into distances between the vowels in an n-dimensional space using two-way multidimensional scaling. Results for each vowel set showed that the physical stimulus space, which was specified by the two parameters F1 and F2, was always mapped into a two-dimensional perceptual space. The best metric for modeling the perceptual distances was the Euclidean distance between F1 and F2 in barks. The second experiment investigated the perception of the same vowels from the first experiment, but embedded in a consonantal context. Following the same procedures as experiment 1, listeners' perception of the (bv) dissimilarities was not different from their perception of the isolated vowel dissimilarities. The third experiment investigated dissimilarity judgments for the three vowels (ae-alpha-lambda) located symmetrically in the F1 X F2 vowel space. While the perceptual space was again two dimensional, the influence of phonetic identity on vowel difference judgments was observed. Implications for determining metrics for subphonemic vowel differences using multidimensional scaling are discussed.

Adult↗
PubMed1991

Assimilation and contrast in the phonetic perception of vowels.

The perceptual mechanisms of assimilation and contrast in the phonetic perception of vowels were investigated. In experiment 1, 14 stimulus continua were generated using an /i/-/e/-/a/ vowel continuum. They ranged from a continuum with both ends belonging to the same phonemic category in Japanese, to a continuum with both ends belonging to different phonemic categories. The AXB method was employed and the temporal position of X was changed under three conditions. In each condition ten subjects were required to judge whether X was similar to A or to B. The results demonstrated that assimilation to the temporally closer sound occurs if the phonemic categories of A and B are the same and that contrast to the temporally closer sound occurs if A and B belong to different phonemic categories. It was observed that the transition from assimilation to contrast is continuous except in the /i'/-X-/e/ condition. In experiment 2, the total duration of t 1 (between A and X) and t 2 (between X and B) was changed under five conditions. One stimulus continuum consisted of the same phonemic category in Japanese and the other consisted of different phonemic categories. Six subjects were required to make similarity judgements of X. The results demonstrated that the occurrence of assimilation and contrast to the temporally closer sound seemed to be constant under each of the five conditions. The present findings suggest that assimilation and contrast are determined by three factors: the temporal position of the three stimuli, the acoustic distance between the three stimuli on the stimulus continuum, and the phonemic categories of the three stimuli.

Adult↗
PubMed1994

Selective acoustic phonetic impairment and lexical access in an aphasic patient.

The relationship between acoustic-phonetic disturbances and lexical access was explored in an aphasic patient. M.L. had a restricted disturbance of phonemic discrimination that affected the discrimination of voicing contrasts in nonword stimuli. Despite this impairment, her discrimination of voicing contrasts in words and her comprehension of auditorily presented words containing voiced segments was excellent. Performance on lexical decision was impaired: M.L.'s rejection of nonwords was poor and her reaction times and error rates for word stimuli showed a trend toward being influenced by the lexical status (word or nonword) of the item that would be formed by a change in voicing. The results are consistent with a role for a phonemic code in auditory word recognition, coupled with lexical-to-acoustic/phonetic feedback, but are also compatible with the view that other access codes for the Phonological Input Lexicon are also available.

Aged↗
PubMed1994

Automatic discrimination of phonetically relevant and irrelevant vowel parameters as reflected by mismatch negativity.

An auditory event-related brain potential called mismatch negativity (MMN) was measured to study the perception of vowel pitch and formant frequency. In the MMN paradigm, deviant vowels differed from the standards either in F0 or F2 with equal relative steps. Pure tones of corresponding frequencies were used as control stimuli. The results indicate that the changes in F0 or F2 of vowels significantly affected the MMN amplitudes. The only variable significantly affecting the MMN latencies was sex which, however, did not have any effect on the amplitudes of the MMN. As expected, the MMN amplitudes increased with an increase in the acoustical difference between the standards and the deviants in all cases. On the average, the amplitudes were lower for the vowels than for the pure tones of equal loudness. However, in vowels, minor frequency changes in F0 produced higher MMN amplitudes than similar relative changes in F2. It was also noted that even the smallest and phonetically irrelevant change in F2 was detected by the MMN process. In overall, the results demonstrate that the MMN can be measured separately for F0 and F2 of vowels, although the MMN responses show large interindividual differences.

Adult↗
PubMed1998

Fundamental frequency during phonetically governed devoicing in normal young and aged speakers.

Age-related changes in the laryngeal system can be perceived as altered vocal pitch and increased pitch variability. However, reports vary as to the nature and extent of an age effect on fundamental frequency (F0) for analyses taken over long segments of connected speech. Analysis of F0 across a smaller time frame may be more informative. Young speakers show an increase in F0 associated with phonetically governed devoicing gestures that is likely mediated by increased vocal fold stiffness. Anatomic and neurophysiologic changes in the aged larynx may limit the role of increased vocal fold stiffness in the devoicing gesture. This study tests the hypothesis that aged speakers show a smaller increase in F0 in association with the devoicing gesture for production of an intervocalic voiceless obstruent than do young speakers. Normal young and aged speakers produced a short sentence containing an intervocalic voiceless obstruent. Measures of F0 were obtained for ten cycles before voice offset and ten cycles after voice onset. Young speakers showed a small increase in F0 during devoicing whereas aged speakers showed a decrease in F0 during devoicing. Aged speakers seem to rely more on vocal fold abduction rather than a combination of abduction and tensing to achieve devoicing.

Adult↗
PubMed1999

Integrality of nasalization and F1. II. Basic sensitivity and phonetic labeling measure distinct sensory and decision-rule interactions.

In vowel perception, nasalization and height (the inverse of the first formant, F1) interact. This paper asks whether the interaction results from a sensory process, decision mechanism, or both. Two experiments used vowels varying in height, degree of nasalization, and three other stimulus parameters: the frequency region of F1, the location of the nasal pole/zero complex relative to F1, and whether a consonant following the vowel was oral or nasal. A fixed-classification experiment, designed to estimate basic sensitivity between stimuli, measured accuracy for discriminating stimuli differing in F1, in nasalization, and on both dimensions. A configuration derived by a multidimensional scaling analysis revealed a perceptual interaction that was stronger for stimuli in which the nasal pole/zero complex was below rather than above the oral pole, and that was present before both nasal and oral consonants. Phonetic identification experiments, designed to measure trading relations between the two dimensions, required listeners to identify height and nasalization in vowels varying in both. Judgments of nasalization depended on F1 as well as on nasalization, whereas judgments of height depended primarily on F1, and on nasalization more when the nasal complex was below than above the oral pole. This pattern was interpreted as a decision-rule interaction that is distinct from the interaction in basic sensitivity. Final consonant nasality had little effect in the classification experiment; in the identification experiment, nasal judgments were more likely when the following consonant was nasal.

Humans↗
PubMed1999

Temporal encoding of the voice onset time phonetic parameter by field potentials recorded directly from human auditory cortex.

Voice onset time (VOT) is an important parameter of speech that denotes the time interval between consonant onset and the onset of low-frequency periodicity generated by rhythmic vocal cord vibration. Voiced stop consonants (/b/, /g/, and /d/) in syllable initial position are characterized by short VOTs, whereas unvoiced stop consonants (/p/, /k/, and t/) contain prolonged VOTs. As the VOT is increased in incremental steps, perception rapidly changes from a voiced stop consonant to an unvoiced consonant at an interval of 20-40 ms. This abrupt change in consonant identification is an example of categorical speech perception and is a central feature of phonetic discrimination. This study tested the hypothesis that VOT is represented within auditory cortex by transient responses time-locked to consonant and voicing onset. Auditory evoked potentials (AEPs) elicited by stop consonant-vowel (CV) syllables were recorded directly from Heschl's gyrus, the planum temporale, and the superior temporal gyrus in three patients undergoing evaluation for surgical remediation of medically intractable epilepsy. Voiced CV syllables elicited a triphasic sequence of field potentials within Heschl's gyrus. AEPs evoked by unvoiced CV syllables contained additional response components time-locked to voicing onset. Syllables with a VOT of 40, 60, or 80 ms evoked components time-locked to consonant release and voicing onset. In contrast, the syllable with a VOT of 20 ms evoked a markedly diminished response to voicing onset and elicited an AEP very similar in morphology to that evoked by the syllable with a 0-ms VOT. Similar response features were observed in the AEPs evoked by click trains. In this case, there was a marked decrease in amplitude of the transient response to the second click in trains with interpulse intervals of 20-25 ms. Speech-evoked AEPs recorded from the posterior superior temporal gyrus lateral to Heschl's gyrus displayed comparable response features, whereas field potentials recorded from three locations in the planum temporale did not contain components time-locked to voicing onset. This study demonstrates that VOT at least partially is represented in primary and specific secondary auditory cortical fields by synchronized activity time-locked to consonant release and voicing onset. Furthermore, AEPs exhibit features that may facilitate categorical perception of stop consonants, and these response patterns appear to be based on temporal processing limitations within auditory cortex. Demonstrations of similar speech-evoked response patterns in animals support a role for these experimental models in clarifying selected features of speech encoding.

Auditory Cortex↗
PubMedDate not supplied

Acquisition of serial complexity in speech production: a comparison of phonetic and phonological approaches to first word production.

Comparison was made between performance-based and competence-based approaches to the understanding of first word production. The performance-related frame/content approach is representative of the biological/functional perspective of phonetics in seeking explanations based on motor, perceptual and cognitive aspects of speech actions. From this perspective, intrasyllabic consonant-vowel (CV) co-occurrence patterns and intersyllabic sequence patterns are viewed as reflective of biomechanical constraints emerging from mandibular oscillation cycles. A labial-coronal sequence effect involved, in addition, the problem of interfacing the lexicon with the motor system, as well as the additional problem of initiation of movement complexes. Competence-based approaches to acquisition are within the generative phonological tradition; involving an initial assumption of innate, speech-specific mental structures. While various current phonological approaches to acquisition involve consideration of sequence effects and intrasyllabic patterns, they do not adequately establish the proposed mental entities in infants of this age, and are nonexplanatory in the sense of not considering the causes of the structures and constraints that they posit.

Child Language↗
PubMed1989

Phonetic analysis of the stød in standard Danish.

This paper presents an acoustic and physiological analysis of the Danish 'stød' with an introduction on its phonological role and distribution. The stød is a prosodic feature bound to definite syllables in certain word types and connected to the latter part of the syllable. Phonetically it is a phonation type related to creaky voice. The first part of the syllable is characterized acoustically by a higher pitch level and often a higher intensity level than syllables without stød, and by a relatively high subglottal pressure and airflow, thus generally by a relatively high expenditure of energy. In the second part, the stød phase proper, there is a considerable decrease in intensity, particularly in the lower part of the spectrum and, for the majority of the speakers, a noticeable decrease in fundamental frequency, and/or aperiodicity. Moreover the airflow is low, and inverse filtering shows a longer closure time in each vibration. There is also a slight decrease in subglottal pressure, and all speakers have a constriction of the vocal folds and often of the ventricular folds as well, but with large interindividual variation as to the degree of constriction. On the boundary between the first and the second phase most speakers have a strong contraction of the vocalis and lateralis muscles, obviously preparing for the glottal constriction of the second phase. The author cannot follow Svend Smith in concluding that a sudden contraction and relaxation of the respiratory muscles resulting in a quick rise and fall in subglottal pressure constitutes the primary factor. There is, rather, an independent contraction of a number of muscles, and neither the high pitch at the beginning nor the fall in pitch and intensity in the second phase can be explained by the subglottal pressure contour. The high pitch level at the beginning may be explained by activity in the cricothyroid, and the decrease in pitch and the low intensity in the second phase is probably due to constriction of the glottis, although the fact that the decrease in intensity starts rather early raises some problems. Finally the question of the origin of the stød is discussed briefly. It is suggested that the stød in Danish perhaps originated from a reinforcement of the first syllable in combination with reduction and loss of a following syllable in Common Scandinavian. The reinforcement may have been accompanied by a rise in pitch, so that developments in different directions (involving stød or tonal accents) were possible.

Adult↗
PubMed1989

Perception and production of English vowels by German learners: instrumental-phonetic support in language teaching.

Results are presented from two experiments which examine the application of instrumental phonetic methods to the needs of the teacher of a foreign language. First, the use of a traditional psychophonetic test procedure as a diagnostic tool is demonstrated. Second, the effect of reading, imitation, and prompted recall on production is examined, and the implications for teaching and pronunciation monitoring discussed.

Adolescent↗
PubMed1993

The phonetic interpretation of tone in Igbo.

This article presents a preliminary study of the phonetic interpretation of tone in Igbo, a Kwa language of southeastern Nigeria. The experimental method varies the speaker's pitch range orthogonally with variation in tonal material, and fits a model to measurements of maxima and minima in the resulting F0 contour. A new interpretation of downstep is proposed as a result.

Female↗
PubMed1994

The influence of language on the acoustic properties of phonetic features: a study of the feature [strident] in Ewe and English.

This study explored the extent to which the acoustic manifestation of a phonetic feature is influenced by the linguistic role that the feature plays in the sound inventory of the particular language. To this end, we investigated the acoustic property associated with the feature [strident] in the production of bilabial and labiodental fricatives in Ewe, and labiodental and alveolar fricatives in English, and explored whether the acoustic manifestation of the feature [strident] varied in the instantiation of [f] in Ewe and English. In Ewe, the feature [strident] plays a contrastive role distinguishing labiodental from bilabial fricatives, whereas in English the feature [strident] does not play a contrastive role. Results showed that a measure of turbulence noise was able to distinguish bilabial and labiodental fricatives in Ewe and labiodental and alveolar fricatives in English. Moreover, the range of values associated with defining the amplitude characteristics for [f] was similar in the two languages. Nevertheless, differences emerged in the acoustic fine structure of the noise amplitude for [f v] in the two languages, with the frequency distribution for the labiodental fricative in Ewe being skewed towards the high amplitude range relative to English. These results suggest that while the fundamental manifestation of the acoustic property is the same across languages, its instantiation may be influenced by the functional role that its associated feature plays in the language.

Adult↗
PubMed1995

Phonetics of intervocalic consonant perception: retrospect and prospect.

This article reviews the production characteristics and perceptual cues of intervocalic consonants as a background for acoustic studies of consonant perception in fluent speech. Data show that in conversation intervocalic consonants occur much more commonly than consonants in initial or final position; all phonetic features are strongly represented. Production characteristics of intervocalic consonants are seen to depend on the tempo and rhythmic conditions of the syllables of which they are components. At a moderate tempo, consonants in syllable-final position combine with the onset consonant of the following syllable. This affects durational characteristics and may be explained by higher energy efficiency of CV units in production. Phonological phenomena are related to the shifts in syllable position and the temporal compensations of intervocalic consonant production. Studies of consonant perception in fluent context have dealt with tempo of utterance, position in word, and rhythmic pattern, as well as phonemic context. Major phenomena are effects of coarticulation, invariance in consonant perception, and cue interaction and masking. Much evidence suggests a dominance of the perceptual cues in the CV portion of VCCV and VCV sequences. We suggest that exploration of perception variables that affect consonants in fluent context would be expedited by reorienting experimental procedures to employ listener adjustment of stimuli, instead of the traditional phoneme identification and discrimination procedures with large sets of constant stimuli. Most of the relevant literature deals with stop consonants. Lateral, rhotic, and nasal consonants also deserve intensive study because of their very frequent occurrence. Theoretical issues of phoneme perceptual invariance and motor vs. auditory theory of perception are discussed in relation to proposed experiments which vary syllable tempo and stress pattern.

Humans↗
PubMed1995

Phonetic and phonological aspects of English affricate production in children with speech disorders.

In this paper we consider phonetic and phonological aspects of the English voiceless affricate /t integral of/ as it is realised by children with developmental speech disorders. The speakers described in the study have normal /t/ but disordered /integral of/ and /t integral of/. Using electropalatography (Reading EPG), we compare the stop and fricative phases of /t integral of/ to independent /t/ and /integral of/. This comparison shows that the place of articulation of /t integral of/ can be predicted from that of independent /integral of/. There is a strict requirement for the affricate's stop release to be homorganic with its fricative phase, irrespective of the place of articulation of independent /t/. Sometimes, there is also an observable coronal gesture during the stop phase of a dorsal affricate indicating the influence of independent /t/. This is predicted by phonological theories in which the affricate is related to both /t/ and /integral of/ but not by theories in which the affricate is merely the stop counterpart go /integral of/.

Adolescent↗
PubMed1997

Internal structure of phonetic categories: effects of speaking rate.

Many studies have shown that listeners process speech in a rate-dependent manner, altering the location of phonetic category boundaries in accord with the acoustic consequences of a change in rate during speech production. In a recent series of papers that focused on a voicing contrast, we reported that the perceptual adjustment for rate is not limited to the region of the category boundary, but extends to well within the category, producing a change in which stimuli are perceived to be the best category exemplars. In the current paper, we provide evidence for the generality of this effect by showing analogous results for a /b/-/w/ contrast, specified by transition duration. The implications of these findings for models of rate-dependent processing are discussed.

Adolescent↗
PubMed2001

Obtaining phonetic transcriptions: a comparison between expert listeners and a continuous speech recognizer.

In this article, we address the issue of using a continuous speech recognition tool to obtain phonetic or phonological representations of speech. Two experiments were carried out in which the performance of a continuous speech recognizer (CSR) was compared to the performance of expert listeners in a task of judging whether a number of prespecified phones had been realized in an utterance. In the first experiment, nine expert listeners and the CSR carried out exactly the same task: deciding whether a segment was present or not in 467 cases. In the second experiment, we expanded on the first experiment by focusing on two phonological processes: schwa-deletion and schwa-insertion. The results of these experiments show that significant differences in performance were found between the CSR and the listeners, but also between individual listeners. Although some of these differences appeared to be statistically significant, their magnitude is such that they may very well be acceptable depending on what the transcriptions are needed for. In other words, although the CSR is not infallible, it makes it possible to explore large datasets, which might outweigh the errors introduced by the mistakes the CSR makes. For these reasons, we can conclude that the CSR can be used instead of a listener to carry out this type of task: deciding whether a phone is present or not.

Databases, Factual↗
PubMed1994

Pre-speech in children with cleft lip and palate or cleft palate only: phonetic analysis related to morphologic and functional factors.

Pre-speech in 35 children with clefts of the lip and palate or palate only were analyzed for place and manner of articulation. Transcriptions were made from tape recorded babbling sequences. Two children without clefts were used as reference. All of the children with clefts were treated according to a regimen of early surgical repair of the velum cleft and delayed closure of the cleft in the hard palate. The frequency of selected phonetic features was calculated. Correlations between phonetic/perceptual and functional and morphological factors were tested. Supraglottal articulation dominated among all the children indicating a sufficient velopharyngeal mechanism. The results also showed correlations between cleft type and place of articulation. Anteriorly placed sounds (i.e., bilabial, dental, and alveolar sounds) occurred frequently among the children with cleft palate only and in the noncleft children. In children with cleft lip and palate, posteriorly placed articulations predominated. It was postulated that early intervention may have a positive effect on articulatory development.

Age Factors↗