Study of temporal correlations in the urban noise monitoring network of milan, italy

The European Life project, called DYNAMAP, has been devoted to provide a real image of the noise generated by vehicular traffic in urban and suburban areas, developing a dynamic acoustic map based on a limited number of low-cost permanent noise monitoring stations. In the urban area of Milan, the system has been implemented over the pilot area named Area 9. Traffic noise data, collected by the monitoring stations, each one representative of a number of roads with similar characteristics (e.g. daily traffic flow), are used to build-up a “real time” noise map. DYNAMAP has a statistical structure and this implies that information captured by each sensor must be representative of an extended area, thus uncorrelated from other stations. The study of the correlations among the sensors represents a key-point in designing the monitoring network. Another important aspect regards the “contemporaneity” of noise fluctuations predicted by DYNAMAP with those effectively measured at an arbitrary location. Integration times heavily affect the result, with correlation coefficients up to 0.8-0.9 for updating times of 1h. Higher correlations are observed when averaging over groups of roads with similar traffic flow characteristics.