Leonardo Lancia

On place assimilation in sibilant sequences: Comparing French and English

Abstract Two parallel acoustic analyses were performed for French and English sibilant sequences, based on comparably structured read-speech corpora. They comprised all sequences of voiced and voiceless alveolar and postalveolar sibilants that can occur across word boundaries in the two languages, as well as the individual alveolar and postalveolar sibilants, combined with preceding or following labial consonants across word boundaries. The individual sibilants provide references in order to determine type and degree of place assimilation in the sequences. Based on duration and centre-of-gravity measurements that were taken for each sibilant and sibilant sequence, we found clear evidence for place assimilation not only for English, but also for French. In both languages the assimilation manifested itself gradually in the time as well as in the frequency domain. However, while in English assimilation occurred strictly regressively and primarily towards postalveolar, French assimilation was solely towards postalveolar, but in both regressive and progressive directions. Apart from these basic differences, the degree of assimilation in French and English was independent of simultaneous voice assimilation but varied considerably between the individual speakers. Overall, the context-dependent and speaker-specific assimilation patterns match well with previous findings.

Automatic quantitative analysis of ultrasound tongue contours via wavelet-based functional mixed models

This paper illustrates the application of wavelet-based functional mixed models to automatic quantification of differences between tongue contours obtained through ultrasound imaging. The reliability of this method is demonstrated through the analysis of tongue positions recorded from a female and a male speaker at the onset of the vowels /a/ and /i/ produced in the context of the consonants /t/ and /k/. The proposed method allows detection of significant differences between configurations of the articulators that are visible in ultrasound images during the production of different speech gestures and is compatible with statistical designs containing both fixed and random terms.

Inter-speaker articulatory variability during vowel-consonant-vowel sequences in twins and unrelated speakers

The purpose of this study is to examine and compare the amount of inter-speaker variability in the articulation of monozygotic twin pairs (MZ), dizygotic twin pairs (DZ), and pairs of unrelated twins with the goal of examining in greater depth the influence of physiology on articulation. Physiological parameters are assumed to be very similar in MZ twin pairs in contrast to DZ twin pairs or unrelated speakers, and it is hypothesized that the speaker specific shape of articulatory looping trajectories of the tongue is at least partly dependent on biomechanical properties and the speakers individual physiology. By means of electromagnetic articulography (EMA), inter-speaker variability in the looping trajectories of the tongue back during /VCV/ sequences is analyzed. Results reveal similar looping patterns within MZ twin pairs but in DZ pairs differences in the shape of the loop, the direction of the upward and downward movement, and the amount of horizontal sliding movement at the palate are found.

Nonlinear Dynamics in Speech Perception

Humans engage in a seemingly endless variety of different behaviors, of which some are found across species, while others are conceived of as typically human. Most generally, behavior comes about through the interplay of various constraints informational, mechanical, neural, metabolic, and so on operating at multiple scales in space and time. Over the years, consensus has grown in the research community that, rather than investigating behavior only from bottom up, it may be also well understood in terms of concepts and laws on the phenomenological level. Such top down approach is rooted in theories of synergetics and self-organization using tools from nonlinear dynamics. The present compendium brings together scientists from all over the world that have contributed to the development of their respective fields departing from this background. It provides an introduction to deterministic as well as stochastic dynamical systems and contains applications to motor control and coordination, visual perception and illusion, as well as auditory perception in the context of speech and music.The history of research on speech perception and speech production is replete with examples of nonlinearities between articulation and acoustics, and between acoustics and perception. These nonlinearities are useful for communication. They allow 1) adequate production of speech sounds and words despite people having different vocal tracts with different resonance capabilities, and 2) adequate word recognition despite variation in the acoustic signal across speakers, emphasis, background noise, etc. Yet context and the listener’s expectancies often strongly influence what is perceived; perception is dynamic, influenced by multiple factors that change slowly or quickly as speech goes on. In this chapter we present a selected history of demonstrations of nonlinearities in speech and attempt to exploit the nonlinearities in order to uncover the dynamics of both perception and production of speech.

Analyzing vocal tract movements during speech accommodation

When two people engage in verbal interaction, they tend to accommodate on a variety of linguistic levels. Although recent attention has focused on to the acoustic characteristics of convergence in speech, the underlying articulatory mechanisms remain to be explored. Using 3D electromagnetic articulography (EMA), we simultaneously recorded articulatory movements in two speakers engaged in an interactive verbal game, the domino task. In this task, the two speakers take turn in chaining bi-syllabic words according to a rhyming rule. By using a robust speaker identification strategy, we identified for which specific words speakers converged or diverged. Then, we explored the different vocal tract features characterizing speech accommodation. Our results suggest that tongue movements tend to slow down during convergence whereas maximal jaw opening during convergence and divergence differs depending on syllable position.

A multimodal approach to the voicing contrast in Turkish: Evidence from simultaneous measures of acoustics, intraoral pressure and tongue palatal contacts

Abstract The aims of the study are to investigate acoustic, aerodynamic and supralaryngeal properties of the voicing contrast in Turkish and to better understand the relation between these factors in the maintenance and inhibition of phonetic voicing. For this purpose, simultaneous recordings were carried out using electropalatography, a piezoresistive pressure transducer and a microphone for six speakers of Turkish. The voiced /d, dʒ/ and voiceless /t, tʃ/ target sounds occurred in word-initial position in intervocalic context. Single time points were selected to study the voicing contrast and its corresponding properties. The most pronounced differences between voiced and voiceless consonants were the relative voicing during closure and the velocity maximum of intraoral pressure (Pio). Phonologically voiced stops showed a relatively long voicing portion, a negative VOT (for /d/) and a slower rise in Pio. Voiceless stops were realized with less voicing, positive VOT (for /t/) and a steep intraoral pressure rise. However, differences were not found for tongue-palatal contact patterns at full closure. The analysis of mutual dependence between articulatory and aerodynamic measures through Generalized Additive Mixed Model (GAMM) showed a linear relation between the two measures in voiced stops and a nonlinear relation for the voiceless. These results are discussed in light of laryngeal-oral coordination and cavity enlargement. Moreover, the different methodological approaches and their benefits are considered.

Studying the link between inter-speaker coordination and speech imitation through human-machine interactions

According to accounts of inter-speaker coordination based on internal predictive models, speakers tend to imitate each other each time they need to coordinate their behavior. According to accounts based on the notion of dynamical coupling, imitation should be observed only if it helps stabilizing the specific coordinative pattern produced by the interlocutors or if it is a direct consequence of inter-speaker coordination. To compare these accounts, we implemented an artificial agent designed to repeat a speech utterance while coordinating its behavior with that of a human speaker performing the same task. We asked 10 Italian speakers to repeat the utterance /topkop/ simultaneously with the agent during short time intervals. In some interactions, the agent was parameterized to cooperate with the speakers (by producing its syllables simultaneously with those of the human) while in others it was parameterized to compete with them (by producing its syllables in-between those of the human). A positive correlation between the stability of inter-speaker coordination and the degree of f0 imitation was observed only in cooperative interactions. However, in line with accounts based on prediction, speakers imitate the f0 of the agent regardless of whether this is parameterized to cooperate or to compete with them.

Coupling relations underlying complex coordinative patterns in speech production

In studying linguistic behavior, we are often faced to complex dynamical patterns arising from the highly coordinated activity of many partially autonomous processes. In this work, we apply a new approach aimed at studying abstract coupling relations coordinating the behavior of dynamical systems governed by goal oriented behavior. The approach, based on an original version of recurrence analysis, allows to deal with the principal difficulties of this task, which are mainly related to the heterogeneity, the lack of separability and the lack of stationarity of the processes under study. The method is validated trough simulations of theoretical systems and it is adopted to capture (1) invariant abstract coupling structure underlying systematically varying trajectories of the speech articulators involved in the production of labial and coronal plosive and fricative consonants (produced at slow and fast speech rate by five German speakers and recorded via electromagnetic articulography); (2) systematic differ...