Comparison of remote ranging techniques for bowhead whale calls in a dispersive underwater sound channel

Abstract

Locating and monitoring marine mammals near anthropogenic sound sources are important tasks with both environmental and operational consequences. This presentation describes how mode filtering (MF) or a blind-deconvolution technique (synthetic time reversal, STR) can be used to determine the range of bowhead whale calls from a single linear vertical array in a dispersive underwater sound channel. The results are based on environmental parameters at the array location, and simulations and ocean recordings of natural whale calls with a nominal bandwidth from 50 to 500 Hz. The passive listening experiments were conducted in the coastal waters near Kaktovik, Alaska, with a 12-element vertical array nominally spanning the middle 60% of the water column. It was deployed in 55-m-deep water alongside distributed arrays of Directional Autonomous Seafloor Acoustics Recorders (DASARs) arranged in triangular grids used to horizontally localize whale calls. A total of 18 naturally occurring whale calls were considered. The estimated call-to-array ranges determined from mode filtering and STR are compared with reference triangulation results from the DASARs. The vertical-array ranging results are generally within ±10% of the DASARs results with the STR results being slightly more accurate than those from mode filtering. [Sponsored by ONR and Shell.]