Luis M. T. Jesus

A parametric study of the spectral characteristics of European Portuguese fricatives

Studies of Portuguese phonetics and phonology indicate that fricatives are central to some interesting features of the language, yet studies of Portuguese fricatives have been few and limited. In this study, Portuguese fricatives were analyzed in ways designed to enhance our description of the language and to increase our understanding of the production of fricatives. Corpora of Portuguese words containing /f, v, s, z, P, W/, nonsense words of the pattern =V1FV2= that follow Portuguese phonological rules, and sustained fricatives were recorded by four native speakers of European Portuguese (two men, two women). Results of analysis show that more than half of the voiced fricatives devoice; devoicing occurs more often in word-final fricatives. Averaged power spectra were computed for all fricatives and parameterized in order to aid comparisons across speaker and across corpus, and to gain insight into the production mechanisms underlying the language-specific variations. Substantial differences were found between spectra of voiced and unvoiced, same-place fricatives. The parameters spectral slope, frequency of maximum amplitude, and dynamic amplitude, derived from previous studies, behaved as predicted for changes in effort level, voicing, and location within the fricative. Changes in syllable stress, however, did not affect the fricatives in a manner consistent with effort level variation. Some combinations were also useful for separating the fricatives by place or by sibilance. r 2002 Elsevier Science Ltd. All rights reserved.

Intelligibility as a Clinical Outcome Measure Following Intervention with Children with Phonologically Based Speech-Sound Disorders.

BACKGROUND The effectiveness of two treatment approaches (phonological therapy and articulation therapy) for treatment of 14 children, aged 4;0-6;7 years, with phonologically based speech-sound disorder (SSD) has been previously analysed with severity outcome measures (percentage of consonants correct score, percentage occurrence of phonological processes and phonetic inventory). Considering that the ultimate goal of intervention for children with phonologically based SSD is to improve intelligibility, it is curious that intervention studies focusing on childrens phonology do not routinely use intelligibility as an outcome measure. It is therefore important that the impact of interventions on speech intelligibility is explored. AIMS This paper investigates the effectiveness of the two treatment approaches (phonological therapy and articulation therapy) using intelligibility measures, both in single words and in continuous speech, as the primary outcome. METHODS & PROCEDURES Fourteen children with phonologically based SSD participated in the intervention. The children were randomly assigned to phonological therapy or articulation therapy (seven children in each group). Two assessment methods were used for measuring intelligibility: a word identification task (for single words) and a rating scale (for continuous speech). Twenty-one unfamiliar adults listened and judged the childrens intelligibility. Reliability analyses showed overall high agreement between listeners across both methods. OUTCOMES & RESULTS Significant improvements were noted in intelligibility in both single words (paired t(6)=4.409, p=0.005) and continuous speech (asymptotic Z=2.371, p=0.018) for the group receiving phonology therapy pre- to post-treatment, but no differences in intelligibility were found for those receiving the articulation therapy pre- to post-treatment, either for single words (paired t(6)=1.763, p=0.128) or continuous speech (asymptotic Z=1.442, p=0.149). CONCLUSIONS & IMPLICATIONS Intelligibility measures were sensitive enough to show changes in the phonological therapy group but not in the articulation therapy group. These findings emphasize the importance of using intelligibility as an outcome measure to complement the results obtained with other severity measures when exploring the effectiveness of speech interventions. This study presents new evidence for the effectiveness of phonological therapy in improving intelligibility with children with SSD.

Acoustic analysis of European Portuguese uvular [χ, ] and voiceless tapped alveolar [] fricatives

In a study of European Portuguese fricatives it was noted that /R, r/ were often realized as [χ,?,?], which are, respectively, unvoiced and voiced uvular fricative, and voiceless tapped alveolar fricative. Although these phones have not previously been recognized as occurring in European Portuguese, they occurred in 115 words out of a corpus of 1304 words, out of which 107 words could be analysed, in recordings made by four native speakers (two men, two women). Time- and frequency-averaged power spectral characteristics are presented, together with a detailed temporal analysis. The frequencies of high-amplitude peaks in the [χ] and [?] spectra clearly indicate a back place of articulation, with median duration across subjects and words of 69 ms and 35 ms. The short (approximately 20ms), noisy acoustic signal in [?] suggests a stop-like manner of articulation, but the turbulence noise characteristics, similar to fricatives, differ from the transient burst noise of plosives.

Temporal acoustic correlates of the voicing contrast in European Portuguese stops

This study focuses on the temporal analysis of stops /p b t d k g/ and devoicing analysis of voiced stops /b d g/ produced in different word positions by six native speakers of European Portuguese. The study explores acoustic properties related to voicing. The following acoustic properties were measured: voice onset time (VOT), stop duration, closure duration, release duration, voicing into closure duration, duration of the preceding vowel and duration of the following vowel. Results suggested that when [b d g] were devoiced, the acoustic properties stop duration, closure duration, duration of the following vowel, duration of the preceding vowel and duration of voicing into closure were relevant for the voicing distinction. Implications for research and practice in speech and language therapy are discussed. Further investigation is needed to find how the productions analysed in the present study were perceived by listeners, specifically productions of devoiced stops.

Análise temporal das oclusivas orais do Português Europeu: um estudo de caso de normalidade e perturbação fonológica

PURPOSE: this paper submits a study on the duration of the different phases of stops produced by two children, one of them with phonological disturbance (speaker 2). METHODS: the corpus includes 54 real words, with stop consonants in initial, medial and final position. In this study two of European Portuguese (EP) native speakers, aged between seven and eight years, took part. RESULTS: the results for the EP speaker 1 showed that the total duration of voiceless stop consonants was greater than voiced stop consonants. The VOT was, in general, larger for voiceless stops than in voiced stop consonant. Speaker 2 (with phonological disorder) devoiced the stop [g], and the stop consonant [d] was devoiced in initial position and voiced in medial and final position. The stop consonant [b] was normally voiced. CONCLUSION: most of the analyzed durations show similar values for both speakers.

Simulation of human speech production applied to the study and synthesis of European Portuguese

A new articulatory synthesizer (SAPWindows), with a modular and flexible design, is described. A comprehensive acoustic model and a new interactive glottal source were implemented. Perceptual tests and simulations made possible by the synthesizer contributed to deepening our knowledge of one of the most important characteristics of European Portuguese, the nasal vowels. First attempts at incorporating models of frication into the articulatory synthesizer are presented, demonstrating the potential of performing fricative synthesis based on broad articulatory configurations. Synthesis of nonsense words and Portuguese words with vowels and nasal consonants is also shown. Despite not being capable of competing with mainstream concatenative speech synthesis, the anthropomorphic approach to speech synthesis, known as articulatory synthesis, proved to be a valuable tool for phonetics research and teaching. This was particularly true for the European Portuguese nasal vowels.

Devoicing measures of European portuguese fricatives

This paper presents a study of devoicing of European Portuguese fricatives. Two devoicing criteria (a manual criterion and a criterion based on the ratio of variances of the laryngograph signal during the VF transition and during the fricative) were used to classify the examples into two or three categories. The results of the automatic and manual measures of devoicing are compared, and an explanation for observed misclassifications is presented. Devoicing occurs extensively in Portuguese; results are compared to those for English.

Weak voicing in fricative production

Understanding of the production mechanisms of voiced fricatives lags significantly behind that of other phonemic categories of speech. This paper presents a new voicing classification criterion to distinguish the voicing in fricatives from that of their contextual vowels in VCV tokens: weak vs strong voicing. The criterion is based on the oral airflow, distinguishing it from previous criteria based jointly on the acoustic and EGG signals. Aerodynamic and EGG recordings of four normal adult speakers (two females and two males), producing a speech corpus of 9 isolated words with the European Portuguese (EP) voiced fricatives /v, z, ?/ in word-initial, -medial and -final position, and the same 9 words embedded in 42 different real EP carrier sentences, were analysed. Fricatives were characterised in terms of oral airflow, fundamental frequency, first formant intensity level and glottal open quotient in absolute terms and relative to the values found in their surrounding vowels. The voicing during fricative production presented properties distinct from the voicing of the contextual vowels, leading to the development of a classification criterion based on the relative amplitude of the oscillations in the oral airflow signal. This contributes to distinguish voicing in fricatives from the modal voicing of the vowels

(Non-)retroflex Slavic affricates and their motivation: Evidence from Czech and Polish

The Slavic affricate represented by /c/ is tacitly or explicitly assumed to be / / for all Slavic languages. In this paper we revise the affricate inventories of Polish and Czech, showing that the symbol /c/ stands for two different sounds: the palatoalveolar / / in Czech and the retroflex / / in Polish. This conclusion is supported by acoustic results for Polish and Czech data. The fact that COG (centre of gravity) values of frication are not significantly different for Polish and Czech /c/ appears a bit surprising especially in light of the fact that COG is generally seen as a parameter contributing to the distinction of fricatives (including sibilants, see e.g. Gordon, Barthmaier & Sands 2002). Our results show that other parameters such as duration of the frication phase, F1 and F2 of the following vowel as well as spectral slopes are more reliable cues for distinguishing the small differences between affricates examined here.

Stop and Fricative Devoicing in European Portuguese, Italian and German

This paper describes a cross-linguistic production study of devoicing for European Portuguese (EP), Italian, and German. We recorded all stops and fricatives in four vowel contexts and two word positions. We computed the devoicing of the time-varying patterns throughout the stop and fricative duration. Our results show that regarding devoicing behaviour, EP is more similar to German than Italian. While Italian shows almost no devoicing of all phonologically voiced consonants, both EP and German show strong and consistent devoicing through the entire consonant. Differences in consonant position showed no effect for EP and Italian, but were significantly different for German. The height of the vowel context had an effect for German and EP. For EP, we showed that a more posterior place of articulation and low vowel context lead to significantly more devoicing. However, in contrast to German, we could not find an influence of consonant position on devoicing. The high devoicing for all phonologically voiced stops and fricatives and the vowel context influence are a surprising new result. With respect to voicing maintenance, EP is more like German than other Romance languages.