My primary research interests lie in the area of Acoustics, with particular emphasis on Underwater Acoustics, Array Signal Processing, and Animal Bioacoustics.
Click on a topic for more information.
Array Signal Processing
- Ranging of Bowhead Whale Calls using a Vertical Array
- Shima H. Abadi, Aaron M. Thode, Susanna B. Blackwell, David R. Dowling: "Remote ranging of bowhead whale calls in a dispersive underwater sound channel", Journal of the Acoustical Society of America, Vol. 136, Issue 1.
- Ranging of Low Frequency Baleen Whale Calls using a Long Horizontal Array
Bowhead whale call localization
The localization of marine mammals is important for biological studies and for assessments of the impact of anthropogenic activities on the marine environment. Passive acoustic monitoring (PAM) has become an increasingly popular method for localizing certain marine mammal species that are acoustically active. The bowhead whale (Balaena mysticetus) is one such species, generating a large variety of calls, including impulsive and frequency-modulated (FM) sweeps, during its spring and fall migrations between the Bering and Beaufort Seas in Alaska.
This research compares the performance of three methods for estimating the range of broadband (50-500 Hz) bowhead whale calls in a nominally 55 m deep waveguide: conventional mode filtering (CMF), synthetic time reversal (STR) , and triangulation. This study uses simulations and acoustic data collected in 2010 from coastal waters near Kaktovik, Alaska. At the time a 12-element vertical array, spanning the bottom 60% of the water column, was deployed alongside a distributed array of 7 Directional Autonomous Seafloor Acoustics Recorders (DASARs).
A total of 19 bowhead whale calls were analyzed with frequencies in the range 50-500 Hz, which – at the low frequency end – is close to the cut-off frequencies of all propagating modes of the ocean sound channel. Table I lists each call's bandwidth, SNR, and ranges from CMF, STR, and triangulation (plus estimated uncertainties).
This table shows that the vertical-array ranging results are generally within ±10% of the DASAR results, with the STR results providing slightly better agreement with the DASAR results. The results also indicate that a single vertical array can range calls over larger ranges and with greater precision than a standard distributed array, whenever the call locations are beyond the distributed array boundaries.
More details in:
- Studying the Impact of Seismic Reflection Surveys on Baleen Whales (coming soon)