Exploiting ambient noise for coherent processing of mobile vector sensor arrays

Abstract

A network of mobile sensors, such as vector sensors mounted to drifting floats, can be used as an array for locating acoustic sources in an ocean environment. Accurate localization using coherent processing on such an array dictates the locations of sensor elements must be well-known. Achieving this for a mobile, submerged array composed of individual drifting sensors is usually challenging. However the coherent processing of the ambient acoustic noise between sensor pairs can provide the separation distance between them and thus an opportunity to correct sensor location errors. Here a stochastic search algorithm is presented for identifying hidden coherent noise arrivals when the separation distance is changing faster than the required averaging time to extract such arrivals from a fixed sensor pair. The accuracy of this method matches that of GPS-derived array element positioning and its performance is shown to be improved when using directional vector sensors instead of omnidirectional hydrophones. The proposed approach is demonstrated experimentally using ambient noise recorded by drifting vector sensors deployed in the Long Island Sound and is used to enable tracking of surface ships by coherent processing of the drifting sensors.