Time reversal for source detection in urban environment

Abstract

This paper applies the time reversal method to acoustic source detection in an outdoor urban environment. Experimental measurements were conducted in a full-scale artificial village to determine the effect of buildings on sound propagation outdoors. Explosive charges were detonated to produce acoustic pulses that were digitally recorded by sensors scattered throughout the village. We use the two-dimensional finite difference time domain (FDTD) method to compute synthetic time traces for acoustic propagation within the artificial village. The FDTD model predicted arrival times and amplitude levels that are in fair agreement with the measured data at most microphone measurement locations. Using the simulated time traces and the measured data from only nine stations and back propagating them into the model, the sound energy refocuses in the vicinity of the true source location. Our time reversal experiment confirms that the phase information is more critical than sound pressure levels and that using information acquired only at non-line-of-sight (NLOS) locations is sufficient to obtain accurate source locations. The results demonstrate that time reversal can potentially be used for fast source location in a complex urban terrain and noisy acoustic background, with without requiring LOS sensors. [Work funded by U.S. Army.]