Louis-Jean Boë

Articulatory–acoustic relationships during vocal tract growth for French vowels: Analysis of real data and simulations with an articulatory model

Abstract This paper reports on the articulatory–acoustic relationships involved during vocal tract growth. Data were taken from a database of ten French vowels uttered by 15 speakers ranging in age from 3 years old to adulthood. Despite the important acoustic variation encountered, one feature is displayed by all the speakers: the production of extreme focal vowels /i/, /u/, /a/, and /y/, realized with a strong concentration of spectral energy related to the proximity of two formant peaks. This feature represents an acoustic goal guiding the speakers task. Our simulations using an articulatory model demonstrate that the realization of the focalization feature may require different articulatory gestures for young children compared to adults, consisting of adaptive articulatory strategies exploited to compensate for the small pharynx of the former. Perceptual tests show that achieving focalization results in a lower intelligibility for the children than for the adults. Due to the relatively shorter pharyngeal cavity of the child compared to the adult, focalization cannot be achieved together with the perceptual objective related to rounded vowels /y/ in French. Results are discussed in light of the dispersion-focalization theory and the perception for action control theory (PACT).

Asymmetries in vowel perception, in the context of the Dispersion–Focalisation Theory

In a recent paper in this journal, Polka and Bohn [Polka, L., Bohn, O.-S., 2003. Asymmetries in vowel perception. Speech Communication 41, 221–231] display a robust asymmetry effect in vowel discrimination, present in infants as well as adults. They interpret this effect as a preference for peripheral vowels, providing an anchor for comparison. We discuss their data in the framework of the Dispersion–Focalisation Theory of vowel systems. We show that focalisation, that is the convergence between two consecutive formants in a vowel spectrum, is likely to provide the ground for anchor vowels, by increasing their perceptual salience. This enables to explain why [y] is an anchor vowel, as well as [i], [a] or [u]. Furthermore, we relate the asymmetry data to an old experiment we had done on the discrimination of focal vs. non-focal vowels. Altogether, it appears that focal vowels, more salient in perception, provide both a stable percept and a reference for comparison and categorisation.

Detecting Anticipatory Events in Handwriting Movements

We investigated how visual processes exploit specific anticipatory movements observed in handwriting gestures. Previous research has shown that the kinematic information contained in the downstroke of an l is exploited to predict the identity of the forthcoming letter. Here, we determined the moment at which prediction takes place. Two between-letter effects were examined: changes in size (ll vs le) and changes in rotation direction (le vs ln). Results show that with only 75% of the l downstroke trajectory (or 60% of the downstroke time) subjects are already capable of predicting the identity of the letter following the l, that is well before the end of the downstroke. Analysis also reveals that identification takes place after the presentation of the movement acceleration phase. The visual perception of motor anticipation seems to involve the detection of motor events.

Infants' vocalizations analyzed with an articulatory model: A preliminary report

Abstract Articulatory exploration enables the infant to discover abilities of the vocal tract and learn relationships between movements and percepts. However, neither direct measurements nor transcription methods have access to tongue configurations in pre-linguistic infant vocalizations. A statistical articulatory–acoustic model integrating the non-linear growth of the human vocal tract was used to describe infant behavior before and at the beginning of canonical babbling. Analyses were developed to assess from a set of (F1, F2) formant frequencies reported at 4 and 7 months in two separate corpora the most likely articulatory degrees of freedom of the model. Results indicate that exploration in the 4-month corpus is centered around a neutral configuration. It involves at least three articulatory parameters, including at least one for the tongue. The jaw seems to play a minor role in this exploration. In contrast, in the 7-month corpus, the exploration range increases: in this case the jaw plays a dominant role, leading to a large exploitation of the open–close contrast and associated F1 diversification in formant space. The simulation of co-occurrences between closants and vocants from the 7-month corpus in the framework of the Frame-Content theory provides a portrait largely consistent with previously reported experimental data. Locus scatter-plots were also simulated and compared to available data on development of coarticulation in CV syllables. This kind of analysis could be applied to corpora of infants’ vocalizations at various ages to understand the development of speech production in relation to the growth of the human vocal tract.

Forensic voice identification in France

Abstract Among the sources of information used in legal identification, fingerprints and genetic data seem to provide a high degree of reliability. It is possible to evaluate the probability of confusing two individuals who might possess the same fingerprint characteristics or the same genetic markers, and to quantify the risk of a false alarm. By their very nature, these data do not vary significantly over the course of time, and they cannot be modified by a suspect. The erroneous metaphoric term “voiceprint” leads many people (not only the general public) to believe that the voice is as reliable as the papillary ridges of the fingertips. This is not the case. According to present evidence, certain magistrates in France attach far too much importance to analyses of the voice which, along with other indices, should not be used except to help in directing an investigation. In this communication, the author will detail the conditions under which, in France, voice analyses are carried out in the course of an investigation undertaken by the law, and will attempt to define the limits of this protocol, and the difficulty (and impossibility) of producing a reliable statistical test. A historical review will then be presented of the discussions initiated by and position statements adopted by the French speech community since 1900. Finally some ideas and proposals will be put forward in conclusion, which might be discussed by specialists in speech in collaboration with the police, the gendarmerie , and the magistrature , on a national, European, and international level, to advance the search for legal proof of identification within a scientific framework, and to end up with well-defined protocols.

Comments on “distinctive regions and modes: a new theory of speech production” by M. Mrayati, R. Carre´ and B. Gue´rin

Abstract Mryati et al. use the properties of the sensitivity functions of a cylindrical tube to divide it into eight specific regions associated to the eight possible combinations of the sensitivity of the first three resonances. Bringing out acoustic properties of symmetry and compensation, they claim that the production of vowels and consonants is based on these geometric and acoustic properties, since the eight regions can be linked to morphological and articulatory properties of the vocal tract. The authors formulate a new vowel production theory and they propose a universal phonological system for consonants. We are critical of the New Theory on several counts: • - the limitations of sensitivity functions have been overlooked; • - the generalizations are anthropomorphically weak; • - the predictions fail to match known acoustic facts; • - the universal classification is in contradiction with basic phonetic knowledge. More generally this kind of approach seems intrinsically very limited: the vocal tract is not a series of tubes whose dimensions can be manipulated independently, without referring to an underlying articulatory model integrating articulatory constraints. The New Theory will retain all of its value once it has been returned to its natural context i.e. the simple acoustic description of the vocal tract around the neutral position and as a tool for speech synthesis.