Stabilization Time of Running Equivalent Level LAeq for Urban Road Traffic Noise

In urban areas, noise levels can largely vary in space and time due to the great complexity of these environments. The time required for the fluctuations of the running equivalent level LAeq to be limited within a preset variability range is a key issue for determining a statistically representative sample of the urban acoustic environment. The goal of the present study is to evaluate the potential of the stabilization time, defined as the minimum time ST after which the difference between the corresponding continuous equivalent sound pressure level LAeq,ST and the continuous equivalent sound pressure level LAeq,T referred a longer time T, including ST, is never greater than a preset uncertainty interval ε. For this purpose, a dataset of road traffic noise continuously monitored in 97 sites in the city of Milan, Italy, is considered, providing 268 time series of 1 s short LAeq,1s, each lasting 24 h. The stabilization time ST referred the hourly LAeq,1h was determined for three preset uncertainty intervals ε, namely ±0.5, ±1.0 and ±1.5 dB(A). The results are promising and provide useful hints to obtain short-time noise monitoring as a statistically representative sample of the urban acoustic environment and, therefore, can be a tool to increase the low spatial resolution usually achievable by unattended permanent monitoring units.