Dynamic noise maps are asked to accurately represent in real time the noise levels captured by acoustic sensors in urban environments. Thus, the measurement precision of the employed sensors becomes of paramount importance to obtain a reliable picture of the urban noise levels. In this work, a case study designed to validate the accuracy of the Leq values of the low-cost acoustic sensor developed for the DYNAMAP project in real-life conditions is presented. To that effect, simultaneous acoustic measurements have been conducted in the same locations in the Milan’s project pilot area using a Class I sound level meter and the low-cost sensor. The analysis of the parallel acoustic data collected during the recording campaign compares both measuring equipments accounting for traffic noise, background city noise, and non-traffic noise events.