Passive acoustic localization of fish using a compact hydrophone array

Abstract

Passive acoustic monitoring of fish in their natural environment is a research field of growing interest and importance. Although many fish species are soniferous, the characterization and biological understanding of their sounds are largely unknown. Many underwater acoustic recordings contain sounds likely produced by fish, but little information can be extracted from them due to the lack of fundamental knowledge about the behaviors they represent. Deploying small hydrophone arrays can help fill some of these knowledge gaps. Passive acoustic localization using fish calls received on multiple hydrophones can be used to estimate swimming speed, calling rate of individual fish, and source level of their calls. This paper focuses on the three-dimensional localization of fish using a compact array of 6 hydrophones using both simulated and measured data. Fish sounds were detected manually on one of the hydrophones. Time difference of arrivals (TDOAs) were then defined by cross correlating the detected signal with signals from the other hydrophones. Linearized Bayesian inversion was employed to localize fish sounds from the measured TDOAs. Localization uncertainties were below 10 cm inside the hydrophone array. Simulated annealing optimization was used to define the hydrophone configuration that could provide the smallest localization uncertainties.