Analysis of a vehicle-mounted self-stabilized p-u probe as a continuous spatial acoustic impedance measuring system for studying road surfaces

The knowledge of the acoustic impedance of a material allows to calculate its acoustic absorption. Furthermore, it can also be linked to some of the material's structural and physical proprieties by means of adequate models. However, while measuring the acoustic impedance of pavement samples in laboratory conditions can be usually achieved by using high accuracy equipment, such as the impedance tube, a complete insitu evaluation of the paving results less accurate than the laboratory one and is extremely time consuming, enough to make a full scale implementation of in-situ evaluations practically impossible. Such a system would be necessary for evaluating the homogeneity and the correct laying of a road surface, which is proven to be directly linked to its acoustic emission properties. In the presented work, a measurement instrument fixable to a moving laboratory, such as a vehicle, is studied to overcome the issues that afflict in-situ measurements and thus allowing a continuous spatial characterization of a given pavement and a direct evaluation of the surface's quality. A calibration method will be shown, together with the evaluation of the performances of the system as an acoustic measure instrument.