Master thesis on sounds from mammals in the oceans

Nansen Center student Sebastian Menze passed his Master exam at University of Bergen with excellent marks on a thesis within passive marine acoustics. Monitoring of passive acoustic sounds is increasingly used to study the distribution and migration of marine mammals in the oceans.

Marine mammal vocalizations are transient sounds, but the combined vocalization from several mammals in a population adds up to a quasi-continuous “chorus”. Marine mammal choruses can be identified as peaks in ocean ambient noise spectra. In the North Atlantic, the fin whale chorus is commonly observed as peak at 20 Hz. In the master thesis an inversion method using intensities of whale chorus recorded on a limited number of widely spaced single acoustic receivers is developed to localize groups of fin whales. Traditional localization approaches are based on accurate travel time differences measured by vertical acoustic arrays at a minimum of three locations. The new method seems to require a much simpler and less expensive monitoring system, but the capability of the method need more direct verification.

Title of the thesis is: Estimating fin whale distribution from ambient noise spectra using Bayesian inversion. Sebastian Menzes master thesis was formally under the Geophysical Institute at the University in Bergen and part of the Joint Nordic Master in Marine Ecosystem and climate program, in cooperation between UoBergen, University of Iceland, University of Aarhus and University of Faroe Islands. His supervisors were Prof. Corinna Schrum at Geophysical Institute, and Dr. Hanne Sagen and Prof. Halvor Hobæk at the Nansen Center.

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