Effects of COVID-19 outbreak on the sound environment of the city of Milan, Italy

In this paper, we present the results of the noise monitoring in the urban area of Milan, Italy, associated with COVID-19 outbreak. In order to limit the diffusion of the pandemic, Italy adopted growing levels of restrictive measures, which ended with a 41-day lockdown from March 23 to May 3 2020. This action created a new kind of environment including a remarkable reduction of air, water and soil pollutants, together with a partial recovery of the ecosystems otherwise compromised. The presence of a permanent noise monitoring system made of 24 sensors installed in the city of Milan, allowed capturing the changes in the urban sound environment in a pre, during and post-lockdown period (months from February to June 2020). The comparison of the noise levels in terms of both absolute noise levels (Lden) and hourly noise profiles (median over lockdown period) with the same period of 2019, showed a dramatic reduction of the noise levels of approximately 6 dB. Splitting the contribution of all-non-traffic noises or anomalous noise events (ANE) from the recorded noise levels, we observe a greater contribution of the latter during the lockdown period. The use of DYNAMAP noise prediction system over an extended urban area allowed the evaluation of the population exposure to noise, estimating an increase of 14.9% and 16.4% of the exposed population to noises with Lden below 53 dB(A) and Lnight below 45 dB(A) with respect to 2019.