How does the sound heritage of a recent urbanization form? We would like to highlight the various processes involved in constituting the environment of a great urban area : how old and new sounds, specific effects due to the natural environment and the particular sound out- put of the population or infrastructure (roads, railways, industry) combine and leave a mark on the place. One of the principal result of our investigation is that contemporary urbanism creates what we call ambiance shocks. The research (that was carried out in 2008) focused on the new town of Isle d'Abeau, near Lyon, France, which was built in the 1970s. This urban area stretches over 20 kilometres beside the Lyon-Grenoble motorway. The conurbation was designed as an archipelago of built islands in a natural landscape and around old villages. Various urban and architectural forms have taken root in this gently rolling landscape, beside the motorway that runs along the valley bottom. Our aim was to use sounds to explore the sensory identity of this type of new town and to identify options for change in order to give developers a greater awareness of dimensions that are difficult to represent. The study of ambiance shocks, would be then a paradigm to understand the sonic experience of this kind of contemporary urbanism and to find different solutions to integrate or resulve these con- flicts in urban design.