The development of citizen-based approaches to the diagnosis and decision-making on urban noise environments responds to a demand from both local authorities and residents. However, the methods for fostering the involvement of citizens and the valorization of local knowledge have yet to be invented. This article reports on a co-constructed experiment between researchers and local authorities, in the city of Rezé (France), of an urban noise diagnosis based on the residents and the use of the smartphone application NoiseCapture, which allows a participative measurement of sound levels. The framework also includes focus group discussions. The dynamics of the recruitment and data collection phase are analysed, showing the importance of creating public events around the initiative. Maps of noise levels, but also of the presence of sound sources, such as road, rail and air traffic, or animals, are produced in a collaborative way. Finally, the focus group discussions highlight that (i) repeated noise measurement modifies participants’ relationship to sound environments; (ii) NoiseCapture enhances the formation of a group of residents active on noise issues. Such a framework can provide a citizen-based basis for decisions on noise environments; the next step will be to study its adaptability to different territories.

Local authorities are increasingly interested in implementing participatory processes, associating inhabitants in decision-making. The Sonorezé project, involving researchers from the Gustave Eiffel University and the City of Rezé, evaluates the interest of a smartphone application for participatory noise measurement, namely Noisecapture, as a vehicle for this citizen participation in the noise context. The project includes the recruitment of participants, the creation of participatory noise maps integrating different indicators, and the constitution of discussion groups that aim to elaborate concerted proposals regarding noise mitigation. In parallel, one will evaluate how access to this tool modifies the perception that inhabitants have of their soundscape, and facilitates their empowerment and the valorization of their inhabitant knowledge. This communication will present the whole workflow, highlighting how this framework helps to raise awareness of urban noise environments among inhabitants. Then, one will present in detail the dynamics of the recruitment, which amounts to more than 100 participants that performed almost 1000 measurements, at the stage of the first 4 months. The diversity of the participants' profiles, the temporal and spatial heterogeneity in the measurements, are however possibly an obstacle to the production of representative noise maps, which will be discussed in the communication.