Frank Zimmerer

In defense of stylistic diversity in speech research

Abstract Recently, the debate about what kind of speech data is most appropriate for linguistic research has intensified. Generally, with ‘laboratory speech’ defenders on the one hand and ‘natural speech’ proponents on the other, two seemingly clearly distinct phonetic data types have been identified. In this article, this dichotomy is called into question. Results from previous studies on segmental phonetics, prosody and paralinguistics indicate that the data we are using may indeed have had an immense influence on our results. The research papers in the present Special Issue in Journal of Phonetics provide further evidence for the style-dependency of speech data and hence, on our theories and models. Importantly, they also show that some results remain stable independently of the speaking style under investigation. We claim that these findings do not point to an inherent superiority of one particular type of data used in phonetics research. Instead, we argue for a stronger methodological awareness in investigations of speech phenomena and more cautious interpretations of the findings that we make. We also believe that we need a much better understanding of the extent to which our methods and our ways of collecting speech data influence our results. A generally increased methodological awareness and a higher variety of investigated styles of speech will promote our research progress further than a continuing argument for or against using one particular type of speech data.

When BEAT becomes HOUSE: Factors of word final /t/-deletion in German

The deletion and reduction of alveolar /t/ is a phenomenon that has been given considerable attention in the research on speech production and perception. Data have mainly be drawn from spoken language corpora, where a tight control over contributing factors of /t/-deletion is hardly possible. Here, we present a new way of creating a spoken language corpus adhering to some crucial factors we wanted to hold constant for the investigation of word-final /t/-deletion in German. German is especially interesting with regard to /t/-deletion due to its rich suffixal morphology, attributing morphological status to word-final /t/ in many paradigms. We focused on verb inflection and employed a verb form production task for creating a concise corpus of naturally spoken language in which we could control for factors previously established to affect /t/-deletion. We then determined the best estimators for /t/-productions (i.e. canonical, deleted, or reduced) in our corpus. The influence of extra-linguistic factors was comparable to previous studies. We suggest that our method of constructing a natural language corpus with carefully selected characteristics is a viable way for the examination of deletions and reductions during speech production. Furthermore, we found that the best predictor for non-canonical productions and deletions was the following phonological context.

Phonological and morphological constraints on German /t/-deletions

Abstract In running speech, deviations from canonical pronunciations are omnipresent. In extreme cases, segments such as /t/ are deleted altogether. On the other hand, /t/ may have morphological meaning, for instance, as marker of past tense in deal-t. Is it thus less likely that /t/ is deleted in deal t than in monomorphemic words, such as pain t ? Previous research suggests that morphological constraints on /t/-deletions indeed exist in English. However, in languages like German with richer morphology than English, the probability that /t/ with morphological information is deleted seems to be higher, particularly in contexts where /t/-deletion can allow for cluster simplification. Would such phonological effects override morphological constraints on /t/-deletion? To this end, a novel inflectional spoken verb form corpus was constructed in order to analyze the role of phonological and morphological influences on /t/-deletions. Final /t/ was part of suffixes in 2nd and 3rd person singular present tense verb forms (e.g., mach-s t ; mach- t ; ‘make’). Statistical analyses on /t/-deletions revealed that phonological context was highly predictive of /t/-deletions, particularly in cases where cluster simplifications were possible. This was true even in the 3rd person verb forms, where /t/ is morphologically more meaningful than in the 2nd person verb forms, and despite the fact that overall, /t/ was deleted less often in the 3rd than in the 2nd person. Altogether, this suggests that both phonology and morphology may constraint (or predict) /t/-deletions in German, but phonology can override morphological constraints in certain situations.

Do listeners recover "deleted" final /t/ in German?

Reduction and deletion processes occur regularly in conversational speech. A segment that is affected by such reduction and deletion processes in many Germanic languages (e.g., Dutch, English, German) is /t/. There are similarities concerning the factors that influence the likelihood of final /t/ to get deleted, such as segmental context. However, speakers of different languages differ with respect to the acoustic cues they leave in the speech signal when they delete final /t/. German speakers usually lengthen a preceding /s/ when they delete final /t/. This article investigates to what extent German listeners are able to reconstruct /t/ when they are presented with fragments of words where final /t/ has been deleted. It aims also at investigating whether the strategies that are used by German depend on the length of /s/, and therefore whether listeners are using language-specific cues. Results of a forced-choice segment detection task suggest that listeners are able to reconstruct deleted final /t/ in about 45% of the times. The length of /s/ plays some role in the reconstruction, however, it does not explain the behavior of German listeners completely.

Impact of prosodic structure and information density on dynamic formant trajectories in German

This study investigated the influence of prosodic structure and information density (ID), defined as contextual predictability, on vowel-inherent spectral change (VISC). We extracted formant measurements from the onset and offset of the vowels of a large German corpus of newspaper read speech. Vector length (VL), the Euclidean distance between F1 and F2 trajectory, and F1 and F2 slope, formant deltas of onset and offset relative to vowel duration, were calculated as measures of formant change. ID factors were word frequency and phoneme-based surprisal measures, while the prosodic factors contained global and local articulation rate, primary lexical stress, and prosodic boundary. We expected that vowels increased in spectral change when they were difficult to predict from the context, or stood in low-frequency words while controlling for known effects of prosodic structure. The ID effects were assumed to be modulated by prosodic factors to a certain extent. We confirmed our hypotheses for VL, and found expected independent effects of prosody and ID on F1 slope and F2 slope.

The Perceptual Effect of L1 Prosody Transplantation on L2 Speech: The Case of French Accented German.

Research has shown that language learners are not only challenged by segmental differences between their native language (L1) and the second language (L2). They also have problems with the correct production of suprasegmental structures, like phone/syllable duration and the realization of pitch. These difficulties often lead to a perceptible foreign accent. This study investigates the influence of prosody transplantation on foreign accent ratings. Syllable duration and pitch contour were transferred from utterances of a male and female German native speaker to utterances of ten French native speakers speaking German. Acoustic measurements show that French learners spoke with a significantly lower speaking rate. As expected, results of a perception experiment judging the accentedness of 1) German native utterances, 2) unmanipulated and 3) manipulated utterances of French learners of German suggest that the transplantation of the prosodic features syllable duration and pitch leads to a decrease in accentedness rating. These findings confirm results found in similar studies investigating prosody transplantation with different L1 and L2 and provide a beneficial technique for (computer-assisted) pronunciation training.