title: Observations and Bayesian location methodology of transient acoustic signals (likely blue whales) in the Indian Ocean, using a hydrophone triplet.
abstract: A notable sequence of calls was encountered, spanning several days in January 2003, in the central part of the Indian Ocean on a hydrophone triplet recording acoustic data at a 250 Hz sampling rate. This paper presents signal processing methods applied to the waveform data to detect, group, extract amplitude and bearing estimates for the recorded signals. An approximate location for the source of the sequence of calls is inferred from extracting the features from the waveform. As the source approaches the hydrophone triplet, the source level (SL) of the calls is estimated at 187 ± 6 dB re: 1 μPa-1 m in the 15-60 Hz frequency range. The calls are attributed to a subgroup of blue whales, Balaenoptera musculus, with a characteristic acoustic signature. A Bayesian location method using probabilistic models for bearing and amplitude is demonstrated on the calls sequence. The method is applied to the case of detection at a single triad of hydrophones and results in a probability distribution map for the origin of the calls. It can be extended to detections at multiple triads and because of the Bayesian formulation, additional modeling complexity can be built-in as needed.
authors.affiliation: Institut für Meteorologie und Geophysik, University of Vienna, Vienna, Austria.
authors.forename: Ronan J
authors.initials: RJ
authors.lastname: Le Bras
authors.affiliation: Chatelet Resources, Truckee, California 96161, USA.
authors.forename: Heidi
authors.initials: H
authors.lastname: Kuzma
authors.affiliation: Faculty of Engineering, University of Rijeka, Rijeka, Croatia.
authors.forename: Victor
authors.initials: V
authors.lastname: Sucic
authors.affiliation: Institut für Meteorologie und Geophysik, University of Vienna, Vienna, Austria.
authors.forename: Götz
authors.initials: G
authors.lastname: Bokelmann
mesh_terms: D000162:Acoustics / Q000295:instrumentation*; D000818:Animals; D050616:Balaenoptera / Q000145:classification / Q000502:physiology*; D001499:Bayes Theorem; D004784:Environmental Monitoring / Q000295:instrumentation*; D004867:Equipment Design; D019156:Indian Ocean; D012815:Signal Processing, Computer-Assisted; D013018:Sound Spectrography; D013045:Species Specificity; D013997:Time Factors; D014159:Transducers; D014828:Vocalization, Animal / Q000145:classification