Measurement of noise from single road vehicle in urban traffic

This work shows the first results of experimental measurements finalized to develop a procedure to verify that the sound level acquired during the transit of a single road vehicle in urban traffic is attributable exclusively to the vehicle examined. The activities performed are part of a project to build a system of real-time monitoring of emissions of pollutants from vehicles in urban areas (project SMELLER). Since an essential feature of this system is that it can be adapted to different environmental conditions, the experimental measurements were conducted at sites with different characteristics in terms of sound propagation environment and at different distances from road axis. The experimental set, in addition to sound level meter, consists of a video camera (plate recognition and anomalies check) and a vehicle speed radar detector. It is assumed that the noise level measured while a vehicle passing at a given speed presents a characteristic time pattern and spectral composition. The purpose of the tests is to identify the threshold values within which we can declare a pass-by measurement as good. The experimental data were reported at a distance of 7.5 m from road, in free field environment and at a speed of 50 km/h (standard conditions of ISO 362-1:2007). Correction factors were determined using results from pass-by simulations executed with a commercial noise prediction software and according to coefficients of HARMONOISE project for each 1/3 octave band