Simulation of passive source localization in near-Arctic conditions using frequency-difference matched field processing

Abstract

Matched Field Processing (MFP) is a well-known technique for passive source localization in complex acoustic environments. It involves correlating array-recorded acoustic fields with replica fields calculated using a model of the acoustic environment, and works well is known environments. However, acoustic signals often depend on unknown environmental details which are not included in the replica-field calculations. The severity of this mismatch increases with frequency and source-array range, and it can cause MFP to fail in the signal band at relevant ranges in the arctic ocean. A proposed remedy to this problem is to utilize the frequency-difference autoproduct of the measured acoustic field instead of the acoustic field itself, and to perform the replica calculations at the difference frequency. The simulated performance of frequency difference MFP is shown for a generic near-Arctic environment at signal frequencies of 200 to 300 Hz, and ranges of 30 to 300 km. Here, mismatch between in the acoustic and replica field is modeled by imposing a range-dependent altimetry and surface sound speed profile to simulate surface ice, and by random time delays applied to each ray-path between the source and each receiver to simulate refractive index fluctuations in the ocean. [Sponsored by ONR.]