Using Nonlinear Time Sampling Of Bowhead Whale Calls To Extract Acoustic Mode Shape And Array Tilt

Conventional passive acoustic tracking techniques require the deployment of multiple instrument packages over wide areas, an expensive and time-consuming process. In 2010 and 2012 a 15-element vertical array was deployed in conjunction with Shell's passive acoustic marine monitoring program. Vertical arrays provide a compact deployment that can range bowhead whale sounds to at least 35 km in the Beaufort Sea. Unfortunately, practical deployments of vertical arrays face several issues, including the need to compensate for vertical array inclination, and incomplete coverage of the water column that makes the use of Strum-Liouville orthogonality problematic. Here bowhead whale signals collected in the Arctic Ocean are used to demonstrate how the use of nonlinear sampling in the time domain can be used to directly invert for array tilt and normal mode shapes from an array that only spans 65% of the water column. This information can then be used to estimate the depth and ranges of calling whales. [Work supported by NPRB, Shell Exploration and Production Company, and Greeneridge Sciences Inc.]