The CNRS-financed authoring system SWANS (Synchronised Web Authoring Notation System), now used in several CercleS centres, was developed by teams from four laboratories as a personalised learning tool for the purpose of making available knowledge about lexical stress patterns and mother-tongue interference in L2 speech production--helping students see what clearly they do not always hear. Studying listening perception is often a novel experience for students, involving syllable recognition, distinguishing strong and weak forms and grappling with the pluri-parametric acoustic features of volume, pitch and length. The objective is to improve listening perception and oral intelligibility in European languages, particularly in the context of authentic case studies, such as those of the EXPLICS project (Socrates), and in debates and papers given at international conferences. Test results with the authoring system have shown that the use of dual coding (synchronised sound and SWANS annotations) can have a permanent destabilizing effect on deviant oral production habits, e.g. final-syllable lengthening in French speakers of English. Some students managed to correct genuinely "fossilised" habits for the first time. This effect is noticeable in controlled contexts (case studies) and less in spontaneous conversation. The implications for continuous assessment via case studies are important as such evaluation is often better contextualized, less stressful, more authentic and more credible than traditional testing. The networked exchange of annotated, synchronised texts announces the emergence of a useful teacher-training tool based on the cooperative analysis of perception problems in video documents. This paper outlines techniques for automatic syllable recognition and recommends a Europe-wide project for raising awareness of the importance of lexical stress patterns in all European languages.