Standard French /R/ is - like most rhotics - characterized by a great deal of variability. According to the literature, its differents realizations are mainly due to proprieties of contiguous phonemes and to its position in the word. These accounts leave unexplained a great deal of realizations labeled as "free variants". Phonetically, it could be realized most frequently as a fricative, a trill, an approximant, voiced, unvoiced or sometimes partially unvoiced.

These troubles in understanding variations of French /R/ imply a number of consequences : learners of French have great difficulties with the acquisition of this sound, Automatic Speech Recognition systems - even though they manage to modelize this sound as a function of its contiguous sounds - use pronunciation dictionaries that are overly simplified for words containing /R/. As for phonological theories, they usually consider it as specific because of, among other reasons, its propensity to fluctuate between obstruents and sonorants.

In the project REPER, we hypothesize that articulatory variation is structured according to a continuum going from voiced approximant to voiceless fricative. Realizations outside this continuum can be explained by a series of prosodic and semantic factors mostly. These different realizations and great sensibility to reduction compared to other phonemes suggests a possible on-going evolution of French /R/. An acoustic target (rather than articulatory) seems to be the most important point of stability across these realizations. This acoustic target is found in formant trajectories of contiguous vowels : a rise in first and third formants.

We will investigate the status of French /R/ in three working packages that complete each other and allow a complete comprehension of the phenomenon :

- A first working package dealing with acoustic analyses of large corpora of approximately a hunded hours of continuous speech (also comparing two styles: journalistic and spontaneous speech, and comparing journalistic french to a corpus of journalistic german in order to evaluate the variation of /R/ in both languages as these two phonemes have some similtudes). All corpora are already available and have been tagged for analysis by the coordinator. Large corpora of continuous speech - and them alone - allow to quantify the different realizations of /R/, the amplitude of its variation along with the number of strategies and their usage. They will also enable to clarify the sources of variations only available in large continuous speech studies such as the grammatical, semantic, pragmatic, syntacic and phonotactic context of /R/.

- The second working package is a multi-sensor physiological analysis (using a controlled corpus) so as to analyze the articulatory gestures of friction (through ultrasound device and piezoelectric accelerometer) and voicing (through the non invasive External PhottoGlottoGraph recently patented by the Laboratory of Phonetics and Phonology) whether they go along that hypothesized continuum going from voiced approximant to voiceless fricative. A comparison between the acoustic target of F1 and F3 raising and the articulatory variability will be discussed . This device ready to use in our laboratory will help determine the intended articulatory gestures and their timing in an articulatory phonology framework. Compared to French liquid /l/, the fricative /Z/ and the plosive /g/, we will compared their voicing and devoicing pattern, as well their approximant realization in specific contexts.