Anisia Popescu
email: anisia.popescu@universite-paris-saclay.fr

Lori Lamel

Ioana Vasilescu

Typological classification of European Portuguese fricatives: a cross-language forced alignment and pronunciation variants study

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Introduction

Romance languages are generally known as "true voicing languages" -implementing the voicevoiceless contrast through the use of the [voice] feature [START_REF] Lisker | A crosslanguage study of voicing in initial stops: Acoustical measurements[END_REF], opposing prevoiced with unaspirated voiceless obstruents. "Aspirating languages", such as most of the Germanic languages, make use of the [spread glottis] feature [START_REF] Jansen | Laryngeal contrast and phonetic voicing: a laboratory phonology approach to English, Hungarian and Dutch[END_REF], contrasting unaspirated, phonetically voiceless obstruents with long-lag aspirated obstruents. There are however exceptions such as Dutch [START_REF] Van Alphen | Acoustical and perceptual analysis of the voicing distinction in Dutch initial plosives: the role of prevoicing[END_REF] or, more recently, European Portuguese (Pape andJesus, 2011, 2015). More specifically, in the latter case, both small scale acoustic studies [START_REF] Jesus | Devoicing measures of european portuguese fricatives[END_REF][START_REF] Pape | Devoicing of phonologically voiced obstruents: is European Portuguese different from other Romance languages[END_REF] and large scale corpus-based studies [START_REF] Wu | Extracting linguistic knowledge from speech: A study of stop realization in 5 Romance languages[END_REF][START_REF] Hutin | When phonetics meets morphology: Intervocalic voicing within and across words in Romance languages[END_REF]) have found higher rates of devoicing of phonemically voiced obstruents in EP than in other Romance languages. Furthermore evidence from voicing profiles shows that while Italian and Spanish voicing probability remains high (close to 1) throughout the obstruent, in EP and German there is a decrease in voicing probability starting with 30% of the obstruent. [START_REF] Pape | Stop and fricative devoicing in European Portuguese, Italian and German[END_REF]Shih andMöbius, 1999, 1998). The present study tests these patterns on a much larger scale (100+ hours of speech) via forced alignment of the speech with the orthographic transcription. EP speech data is aligned using parallel multiple-language acoustic models and pronunciation variants for fricatives to answer the following theoretical research question:

• Does EP fricative voicing show consistency within the Romance languages family, or does it take a different path, more similar to languages that are both genetically and geographically different?

To answer this question we chose one Germanic -German -and one Romance -Italian -language.

The choice of languages mirrors the set of languages tested in the original acoustic study [START_REF] Pape | Stop and fricative devoicing in European Portuguese, Italian and German[END_REF]. Based on the chosen language set we can now fine-tune our experimental research question to:

• Is voicing in EP fricatives more similar to German than to Italian ?

2 Methods

To answer this experimental research question we analyzed an EP corpus consisting of 114 hours of mostly standard dialectal broadcast news speech from TV and radio shows. Multiple sources were used for acquiring the data: LDC, ELRA and international projects. The phone level segmentation was generated using a Portuguese acoustic model, estimated using language-specific annotated (manual transcription) training data and pronunciation dictionaries. The output is a sequence of phone segments with labels selected by aligning the reference transcriptions via a language specific dictionary.

To test whether voicing in EP fricatives is more similar to German than Italian, two additional sets of fricative phone models, one for German and one for Italian, were added in parallel to the original Portuguese one. The phone models for all other phonemes are kept in their original Portuguese form. For each language the acoustic models were all trained on roughly 100 hours of transcribed broadcast news data (Portuguese: 1.1 million word tokens, 46k word types; Italian: 1.8 million word tokens, 58.8k word types; German: 1.8 million word tokens, 90k word types). All three (EP, Italian and German) acoustic models are speaker-, contextand word-position-independent monophone models. Each phone model is a 3-state left-to-right continuous density hidden HMM with Gaussian mixtures with up to 32 Gaussians per state (silences are modeled by a single state with 256 Gaussians).

Each acoustic model used the same acoustic parameterization (cepstral -PLP [START_REF] Hermansky | Perceptual linear prediction (plp) analysis for speech[END_REF] and pitch (F0) features), similar to [START_REF] Lamel | Speech recognition for machine translation in quaero[END_REF]. Figure 1 illustrates the speech modeling and alignment process. By using different combi- phone models were no longer available to the ASR system). Each combination will be described in a different section. If voicing in EP fricatives is indeed more similar to German, as attested by previous acoustic studies, we would expect the system to choose the German fricative phone models to a higher degree than it does the Italian fricative phone models. If, however the opposite stands (i.e., EP voicing does not behave similarly to a Germanic language, but is still related to its sister language Italian), we would expect the system to prefer the Italian fricative phone models. We ran a third experiment which involved using one acoustic model at a time (not in parallel) with the addition of pronunciation variants. The language specific (European Portuguese) dictionary was enriched with pronunciation variants for fricative voicing. For example the Portuguese word /vinho/ -'wine' had two possible pronunciations: the original [viño] and a devoiced variant [fiño].

The procedure is similar to that described for English and French in [START_REF] Lamel | On designing pronunciation lexicons for large vocabulary continuous speech recognition[END_REF][START_REF] Adda | Pronunciation variants across system configuration, language and speaking style[END_REF]. The system then had to choose which phone model (phonetically voiced or phonetically voiceless) best fitted the phonemically voiced fricative in the data. This experiment will be described in section 5.

3 Experiment 1: Three-way choice of acoustic models -European Portuguese,

Italian and German

In this first experiment, for each fricative /v,z / the system was presented with three phone models in parallel, the original EP phone model completed with the German and Italian ones. The system then had to choose which of the three phone models for the phonemically voiced /v,z/ best fitted the acoustic realization of the fricatives in European Portuguese. Figure 3 shows the percentages of selected phone models per language as a function of place of articulation (labiodental /v/, coronal /z/). As expected, the original Portuguese phone model was markedly preferred (83.7% of cases for the labiodental /v/ and 66.9% of cases for the coronal /z/). For the rest of the cases the system preferred either the German or the Italian phone models. For both the labiodental /v/ and the coronal /z/ the German models were preferred. There is an effect of place of articulation with more mismatches (i.e., the original Portuguese model is less preferred) in the case of the more back fricative (coronal /z/).

Experiment 2: Two-way choice of acoustic models -Italian and German

In the second experiment the original EP phone models for fricatives was no longer an option, forcing the ASR system to choose between either an Italian or a German fricative phone model. Figure 4 shows the counts and percentages of phone occurrences aligned with the Italian or the German phone model as a function of place of articulation.

Results mirror those of experiment one, suggesting the German acoustic models seem to be preferred in 89.5% of cases for the labiodental /v/ and 61.7% of cases for the coronal /z/ over the Italian acoustic models. Similar to experiment 1 there is an effect of place of articulation with Italian acoustic models being chosen to a higher degree in the Based on previous acoustic studies, we know that voicing profiles differ based on language: while Italian voicing probability remains high (close to 1) throughout the fricative, the EP and German voicing probability decreases starting with 30% of the fricative [START_REF] Pape | Stop and fricative devoicing in European Portuguese, Italian and German[END_REF]. This suggests that both EP and German exhibit partial devoicing during the fricative, whilst Italian does not. If this is indeed the case we would expect to find higher percentages of voiceless variants when us-ing the Italian acoustic model (i.e., Italian voiceless fricative models better match the partially devoiced phonetically voiced EP fricative).

Figure 5 shows the percentages of phonetically voiceless variants (greyer shades) identified when using the Italian and German voiced-voiceless acoustic models. White shades correspond to the phonetically voiced variants identified by the system. Results yet again confirm the higher degree

Limitations

The goal of the present study was to (in)validate typological classification results derived from small scale acoustic studies on large scale corpus data. The proposed methodology (i.e., using different combinations of trained acoustic phone models) does not permit a direct replication: while the acoustic studies relied on Praat's [START_REF] Boersma | Praat: doing phonetics by computer[END_REF] autocorrelation (AC) pitch extraction algorithm, the present study relies on the acoustic models of the systems, which include multiple acoustic features. An acoustic analysis pinpointing the most relevant acoustic features is needed. A second limitation of the current study is the noninclusion of several acoustic correlates of voicing in the analysis. It is known that adjacent segments, position in the word/syllable and stress have a significant effect on devoicing rates [START_REF] Pape | Devoicing of word-initial stops: a consequence of the following vowel?[END_REF][START_REF] Bybee | Consonant strenghtening: a crosslinguistic survey and articulatory proposal[END_REF][START_REF] Hutin | When phonetics meets morphology: Intervocalic voicing within and across words in Romance languages[END_REF]. The phonological/phonetic context is all the more pertinent given the use of German as a comparison language, whose acoustic correlates for voicing are dependent on word position (word medial vs. initial vs. final) and stress [START_REF] Jessen | Phonetics and Phonology of Tense and Lax Obstruents in German[END_REF][START_REF] Fuchs | Articulatory correlates of the voicing contrast in alveolar obstruent production in German[END_REF].

Positional effects in the case of fricatives are more reduced in the case of EP since the only licensed consonants in coda position are /l/, /r/ and /S/ and word initial /v,z/ are rare (in our data /v/: 1671 tokens and /z/: 122 tokens) and found mainly in loanwords. Stress on the other hand is relevant: EP, like German, and unlike Italian is said to be stress-timed (Cruz-Ferreira, 1999) or partially stressed and partially syllable-timed [START_REF] Frota | On the correlates of rhythmic distinctions: The European/Brazilian Portuguese case[END_REF]. The corpora is not annotated for prosodic information which limits our analysis. Another well known correlate of voicing that has only indirectly been included in the analysis (via the trained acoustic models) is segmental duration. A more detailed analysis including phonological context and duration information is needed to better explain the patterns.

Conclusion

The present study tested whether voicing in European Portuguese fricatives is more similar to Italian, a closely related Romance language, or to German, a more distantly related language, on large scale corpora using ASR acoustic modeling and pronunciation variants. By allowing the system to choose a preferred model when making the alignment we replicated results from small scale acoustic studies that showed EP tends to diverge from other Romance languages when it comes to fricative voicing. The results also show that the effect seems to be modulated by place of articulation, with the more posterior fricative (the coronal /z/) behaving differently than the more anterior labiodental /v/.

Results support the use of speech technology methodologies to replicate and test phonological hypotheses on large amounts of data [START_REF] Yuan | /l/ variation in american english: A corpus approach[END_REF][START_REF] Ryant | Automating phonetic measurement: The case of voice onset time[END_REF].

Figure 1 :

 1 Figure 1: Illustration of the speech modeling and alignment process for the Portuguese word cavar 'to dig'

Figure 2 :

 2 Figure 2: Combination of three acoustic models (Italian, EP and German) for the fricative /v/ in the Portuguese word cavar 'to dig'

Figure 3 :

 3 Figure 3: Percentages of phone occurrences aligned with either the original Portuguese, the Italian or the German acoustic model for the labiodental /v/ (left) and the coronal /z/ (right)

Figure 4 :

 4 Figure 4: Percentages of phone occurrences aligned with either the Italian or the German acoustic model for the labiodental /v/ (left) and the coronal /z/ (right)

Figure 5 :

 5 Figure 5: Percentages of phone occurrences aligned with either the voiceless (grey shades) or the voiced (white shade) for the labiodental /v/ (left columns) and coronal /z/ (right columns) per language (Italian on the left and German on the right)

Acknowledgements

This work was partially supported by the French National Research Agency (ANR) as part of the DIPVAR project (ANR-21-CE38-0019).


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