Algerian Arabic-French bilinguals show phonetic variation with respect to vowel timber in both their languages. Our study aims to automatically identify vowel variants frequently produced by such bilinguals. To that end, the speech corpus FACST, containing French and Algerian Arabic code-switched speech, was analyzed. A second corpus with native French speakers (NCCFr) was used to provide a reference baseline and to compare vowel variants across the two speaker groups. Three experiments were carried out: first, the French speech of both corpora was aligned with a French acoustic model including parallel nearest-neighbor vowel variants in its pronunciation dictionary. Second, the Arabic speech was aligned using the same acoustic model with parallel vowel variants in its dictionary. Finally, we tested whether peripheral vowels in Algerian Arabic-French bilinguals are more often centralized than in French native speech by allowing schwa as a competing variant. The results show that French natives and Algerian Arabic-French bilinguals globally have a comparable amount of vowel variation in French. However, French natives have stable high vowels whereas bilinguals tend to produce stable low and back vowels. In the centralization experiment, Algerian bilinguals favor the centralization of mid, open and back vowels.
French L2 Learners of German (FG) often replace the palatal fricative /ç/ absent in French with the post alveolar fricative /S/. In our study we investigate which cues can be used to distinguish whether FG speakers produce [S] or [ç] in words with the final syllables /IS/ or /Iç/. In literature of German as an L2, to our knowledge, this contrast has not yetbeen studied. In this perspective, we first compared native German (GG) productions of [S] and [ç] to the FG speaker productions. Comparisons concerned the F2 of the preceding vowel, the F2 transition between the preceding vowel and the fricative, the center of gravity and intensity of the fricatives in high and low frequencies. To decide which cues are effectively choices to separate [S] and [ç], the Weka interface in R (RWeka) was used. Results show that for German native speech, the F2 of the preceding vowel and the F2 transition are valid cues to distinguish between [S] and [ç]. For FG speakers these cues are not valid. To distinguish between [S] and [ç] in FG speakers, the intensity of high and low frequencies as well as the center of gravity of the fricatives help to decide whether [S] and [ç] was produced. In German native speech, cues furnished only by the fricative itself can as well be used to distinguish between [S] and [ç].
Evaluating automatic speech recognition (ASR) systems is a classical but difficult and still open problem, which often boils down to focusing only on the word error rate (WER). However, this metric suffers from many limitations and does not allow an in-depth analysis of automatic transcription errors. In this paper, we propose to study and understand the impact of rescoring using language models in ASR systems by means of several metrics often used in other natural language processing (NLP) tasks in addition to the WER. In particular, we introduce two measures related to morpho-syntactic and semantic aspects of transcribed words: 1) the POSER (Part-of-speech Error Rate), which should highlight the grammatical aspects, and 2) the Em-bER (Embedding Error Rate), a measurement that modifies the WER by providing a weighting according to the semantic distance of the wrongly transcribed words. These metrics illustrate the linguistic contributions of the language models that are applied during a posterior rescoring step on transcription hypotheses.
The present electroencephalographical multi-speaker MMN oddball experiment was designed to study the phonological processing of German native and non-native speech sounds. Precisely, we focused on the perception of German /ɪ-iː/, /ɛ-ɛː/, /a-aː/ and the fricatives [ʃ] and [ç] in German natives (GG) and French learners of German (FG). As expected, our results showed that GG were able to discriminate all the critical vowel contrasts. In contrast, FG, despite their high L2 proficiency level, were only marginally sensitive to vowel length variations. Finally, neither GG nor FG discriminated the opposition between [ʃ] and [ç], as revealed by the absence of MMN response. This latter finding was interpreted in terms of low perceptual salience. Taken together, the present findings lend partial support to the Perceptual Assimilation Model for late bilinguals (PAM-L2) for speech perception of non-native phonological contrasts.
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