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M Fourakis

Publications and source records attributed to M Fourakis.

8 recordsLinked to original sources
PubMed1999

Characterizing knowledge deficits in phonological disorders.

To aid the development of finer-grained measures of phonological competence within a representation-based approach to phonology, two aspects of nonsymbolic phonological knowledge (knowledge of the acoustic/perceptual space and of the articulatory/production space) were examined in 6 preschool-age children with phonological disorders and 6 typically developing age peers. To evaluate perceptual knowledge, gating and noise-center tasks were used. Children with phonological disorders recognized significantly fewer words than age peers on both tasks. To evaluate production knowledge, spectral and temporal measures were obtained for CV sequences involving both lingual and labial stop consonants. Group differences on this task (such as larger transition slope values from lingual consonants to vowels for children with phonological disorders) were also observed. These differerences were interpreted as indicating that the children with phonological disorders were less able to maneuver jaw and tongue body separately or that they used "ballistic" (i.e., less controlled) gestures from lingual consonants to vowels than their age peers. These results suggest that phonological knowledge is multifaceted, and that seemingly categorical deficits at one level can be linked to less robust representations at other levels.

Articulation Disorders↗
PubMed1993

An acoustic metric for assessing change in vowel production by profoundly hearing-impaired children.

The purpose of this study was to investigate the feasibility of developing an acoustic metric to assess vowel production in profoundly hearing-impaired children. The approach taken was to develop a metric from acoustic analysis of vowel productions and then compare it with the perceptual ratings of the same productions by listeners. Speech samples were collected from three profoundly hearing-impaired children participating in a longitudinal study that investigated the effectiveness of assistive listening devices upon speech development. The metric used the extracted fundamental and first, second, and third formant frequencies to represent the tokens as points in a three-dimensional auditory-perceptual space modeled after earlier work by Miller [J. Acoust. Soc. Am. 85, 2114-2134 (1989)]. Euclidean distances were determined between each point and the intended vowel, which was represented by coordinates taken from the Peterson and Barney [J. Acoust. Soc. Am. 24, 175-184 (1952)] data for children. The data suggest that the three-dimensional metric provides significant correlations between production and perception.

Child↗
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↗
PubMed1986

A timing model for word-initial CV syllables in Modern Greek.

Measurements of the temporal characteristics of word-initial stressed syllables in CV CV-type words in Modern Greek showed that the timing of the initial consonant in terms of its closure duration and voice onset time (VOT) is dependent on place and manner of articulation. This is contrary to recent accounts of word-initial voiceless consonants in English which propose that closure and VOT together comprise a voiceless interval independent of place and manner of articulation. The results also contribute to the development of a timing model for Modern Greek which generates closure, VOT, and vowel durations for word-initial, stressed CV syllables. The model is made up of a series of rules operating in an ordered fashion on a given word duration to derive first a stressed syllable duration and then all intrasyllabic acoustic intervals.

Greece↗
PubMed1986

An acoustic study of the effects of tempo and stress on segmental intervals in Modern Greek.

Changes in stress and rate of speech have been shown to have different effects on the durations of speech intervals. We examined the effects of such changes on syllable and intrasyllabic segment durations in the word-initial syllable of three-syllable words in Modern Greek, and in conflict with previously reported results for other languages, found rate and stress to have equal effects. We propose that languages may differ in terms of temporal programming in the same sense as they differ in terms of syntactic or phonological rule systems.

Greece↗
PubMedDate not supplied

Acoustic characteristics of Greek vowels.

Five male speakers produced the vowels of Greek at slow and fast tempo, in lexically stressed and unstressed syllables, and in lexically stressed syllables of words appearing in focus position. Duration, fundamental frequency (F(0)), amplitude, and the frequencies of the first (F(1)) and second formant (F(2)) were measured. The effects on these variables of the phonemic category of the vowel, tempo, stress, and focus were examined. The results indicated that the vowel system of Greek follows universal tendencies in terms of duration but not in terms of F(0) and amplitude. Vowels in focus position, when plotted by their F(1) and F(2) frequencies, defined a vowel space larger than that defined by vowels in any other condition.

Adult↗
PubMedDate not supplied

The acoustic vowel space of modern Greek and German.

The spectral characteristics of vowels in Modern Greek and German were examined. Four speakers of Modern Greek and three speakers of German produced four repetitions of words containing each vowel of their native language. Measurements of the fundamental frequency and the first three formats were made for each vowel token. These measurements were then transformed into log frequency ratios and plotted as points in the three-dimensional auditory-perceptual space proposed by Miller (1989). Each vowel token was thus represented by one point, and the points corresponding to each vowel category were enclosed in three-dimensional target zones. For the present corpus, these zones differentiate the five vowels of Modern Greek with 100% accuracy, and the fourteen vowels of German with 94% accuracy. Implications for the distribution of common vowels across languages as a function of vowel density are discussed.

Auditory Perception↗