Passive acoustic measurements of wind velocity and sound speed in air.

Random acoustic fields generated by uncorrelated sources in moving media contain information about the propagation environment, including sound speed and flow velocity. This information can be recovered by noise interferometry. Here interferometric techniques are applied to road traffic noise. Acoustic travel times and their nonreciprocity are retrieved from two-point cross-correlation functions of noise. The feasibility of passive acoustic measurements of wind velocity using diffuse noise is experimentally demonstrated for the first time. The accuracy of the interferometric measurements of sound speed and wind velocity is confirmed by comparison with in situ measurements of wind, air temperature, and humidity.