The management of sound environments is a major challenge for the quality of life of residents (a definition here including city users). Local authorities have regulatory tools at their disposal to manage urban noise pollution, but these are sometimes far removed from the residents' perceptions. The aim of the SonoRezé project is to build on a citizen science approach, based on a triptych of "Local authorities - Residents - Researchers", working together on the diagnosis and management of urban sound environments in the city of Rezé, in Nantes metropolitan area. The approach consists in participatory noise measurements using the NoiseCapture mobile application, and the definition and implementation of actions jointly developed by residents, elected representatives and researchers, with the aim of improving the city's sound environments. The article will present the interdisciplinary and multi-stakeholder methodology involved. Then, two initiated actions will be outlined and discussed: (i) a scientific mediation initiative in schools focusing on the development of perceptual sound maps, (ii) an action on aircraft noise, precising the methodology involving the three parties used to construct the action, as well as some of the results produced, namely a sensitive map, analyses of measurement data and the production of alternative indicators.