Characterization of the road surfaces in real time

The main factor in the propagation of traffic noise is the road surface, where the vehicles generate noise due to the contact between tire and pavement, in addition to the noise produced by the engine.The aim of this work is to obtain the parameters of ground surfaces in real time at different speeds by using an on-board data acquisition system. The system is based on two small microphones with flat response frequency, a small directional speaker, audio interface and a laptop for signal processing.The contribution of this system is to know, in real time, the physical parameters of ground surface measured at different speeds, minimizing the influence of aerodynamic noise. The low cost and its portability make the system to be a very useful tool for noise predictions in outdoors propagation and could be used as a complement instrument in noise mapping.The acoustic impedance was measured by the method recommended by the ANSI S1.18 standard, but with some adjustments. This method consists of measuring the sound level difference from two microphones close to the surface, and calculating the level difference according to an impedance model of the ground.