In the past century, extensive research has been done regarding the sound propagation in Arctic ice sheets. The majority of this research has focused on low-frequency propagation over long distances. Due to changing climate conditions in these environments, experimentation is warranted to determine sound propagation characteristics in, through, and under first-year, thin ice sheets, in shallow water, over short distances. In April 2016 several experiments were conducted approximately 2 km off the coast of Barrow, Alaska on shore-fast, first-year ice, approximately 1 m thick. To determine the propagation characteristics of various sound sources, frequency response functions were measured between a source location and several receiver locations at various distances from 1 m to 1 km. The primary sources used for this experiment were, an underwater speaker with various tonal outputs, an instrumented impact hammer on the ice, and a propane cannon that produced an acoustic blast wave in air. The transmission loss (TL) characteristics of the multipath propagation (air, ice, water) are investigated and reported. Data indicate that TL in frequency bands between 125 and 2000 Hz varied from approximately 3-6 dB per doubling of distance which is consistent with geometrical spreading losses, cylindrical and spherical, respectively.

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Vector sensors utilize a combination of pressure sensors, particle velocity sensors, or both, to determine the acoustic intensity magnitude and direction pointing toward an acoustic source. This acoustic intensity vector is often referred to as the Direction of Arrival (DOA). By combining DOA information from multiple vector sensor measurement locations, a sound source may be instantaneously localized. The majority of vector sensor research has been conducted for underwater applications. A few studies of in-air vector sensors, which utilize multiple microphones, have been conducted; however, the majority of them study stationary sound sources in a laboratory environment or non-real-world settings. The focus of this paper is to study in-air vector sensor capabilities when sensing non-stationary mechanical noise sources—specifically ground vehicles—in a non-laboratory environment where ambient noise may be present. The DOA measurements at multiple vector sensor locations are used to test the acoustic source localization potential for this method.

Prey fish abundances in the Great Lakes are a driver for several agencies commitments to the Council of Lake Committees to support fisheries management. These management decisions have profound economic and social impacts within the Great Lakes region. Fisheries estimates done by echosounders or trawling may be biased due to the propagated noise from large fisheries vessels. In the first year of a four year collaborative study, crewed fisheries vessels and uncrewed Saildrone vessels were used to compare abundance estimates between “loud” and “quiet” vessels. In order to quantify the effects of ship noise on prey fish abundance estimates, a mobile ship noise measurement system was designed and deployed to measure radiated acoustic signatures of several ships in the Great Lakes. This talk will discuss the deployment of a mobile underwater acoustic test range, and show initial results of ship noise measurements from the first year of the program. In addition, an overview of the echosounder abundance results will be given along with plans for future data generation, analysis, and comparison between crewed and autonomous systems.