In previous works, the system developed by CIRA's vibroacoustic Lab for pass-by-noise tests has been described. This system is made of a couple of synchronized acoustic antennas, with 96 ana-log MEMS microphones and one full HD camera for each antenna. The system developed in the national project LOWNOISE, funded by MIUR (Italian Ministry of Education, University and Research) has been used to perform a test campaign on the environmental noise of a FCA Giulietta equipped with two different kind of tyres: common ones and optimized ones (developed by FCA in LOWNOISE project). Tests have been performed in CIRA plant with different car speed start-ing from 20 kmh up to 50 kmh. These tests have shown the capability of the system to recognize and to separate correctly moving car noise sources, their spectral content and to verify the effec-tiveness in reducing the emitted noise of the optimized tyres respect to the common ones (a re-duction of about 3dB and more has been assessed, with benefit increasing with increasing car speed).