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 realimage of the noise generated by vehicular trafficin urban and suburban areas, developing a dynamic acoustic map based on a limited numberof low-cost permanent noise monitoring stations.In the urban area of Milan, the system has beenimplemented over the pilot area named Area 9.Traffic noise data, collected by the monitoringstations, each one representative of a numberof roads with similar characteristics (e.g. dailytraffic flow), are used to build-up a “real time”noise map. DYNAMAP has a statistical structure and this implies that information capturedby each sensor must be representative of an extended area, thus uncorrelated from other stations. The study of the correlations among thesensors represents a key-point in designing themonitoring network. Another important aspectregards 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 timesof 1h. Higher correlations are observed when averaging over groups of roads with similar traffic flow characteristics