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, acoustic recording systems were deployed in Barrow Strait as part of the Defence Research and Development Canada (DRDC) Northern Watch Technology Demonstration Project. Two Starfish Sensor Cubes each with a 1-m cube of seven hydrophones operating in the frequency range of 5-750 Hz, and two single-hydrophone, Autonomous Multichannel Acoustic Recorders (AMAR) providing a 30-kHz signal bandwidth were deployed. The Starfish were deployed for two one-week intervals. One AMAR was deployed for two weeks partially overlapping the Starfish deployment. The second AMAR was deployed for a period of one year with recovery planned for August 2013. The observed underwater noise picture is one of high variability ranging from an extremely quiet to a noisy environment. Noise sources included: A 500-m long iceberg grounded within 500 m of one of the Starfish; a large ice island (4-5 km2) that passed within 4 km of the sensors; a small number of motoring vessels; significant wind events that caused rapid and strong variations in the noise field; and a small number of marine mammal detections. After our departure, a large number of Beluga whales were observed visually. The remaining AMAR may detect these late summer visitors.

In August 2012, a field trial was carried out in Barrow Strait south of Gascoyne Inlet in the vicinity of 74.630 N 91.340 W. Underwater acoustic data was collected using a JASCO Autonomous Multichannel Acoustic Recorder (AMAR) and in-house designed sensor systems called Starfish Cubes. The Starfish Cubes were deployed twice, at different locations, each for one week duration and at depths of approximately 110 m. The Cubes consist of seven hydrophones with 1 m spacing and geometrically configured as three cross-dipoles with a central hydrophone, and have an operational frequency range of 5—750 Hz. During the trial 400 and 500 Hz tones were transmitted from discrete locations at various ranges. By using a beamforming method the tones were used to determine the orientation of the Starfish Cubes during their data collection periods. This enables investigation of the horizontal and vertical directionality of ambient noise. Unique localized sources contributing to the ambient noise are discussed such as a nearby grounded iceberg and a low frequency wandering tonal.

No abstract

Modified international submarine engineering (ISE) explorer AUVs with an endurance of over 400 km are being used to aid in the mapping of the under-ice Arctic seafloor. The explorers are equipped with a DRDC-developed acoustic homing system built into the AUV nose cone. The acoustic receiver consists of seven digital hydrophones arranged in a tri-axis cross-dipole array. A controller/data processor located within the AUV pressure hull handles the real-time acoustic arrival azimuth and elevation estimation, as well as the control and calculations for an on-demand short-range three dimensional (3-D) localization system, and the control of vehicle telemetry data flow. The processor and array consume less than 2 W. A small, easily transportable, DRDC-designed acoustic transducer provides a powerful acoustic homing signal. Using the homing system, the vehicles were able to locate an acoustic beacon at a randomly drifting Ice Camp from a range in excess of 50 km (100-km ranges possible). The design, development, and use of the homing system are described in this paper. In addition, on-going software improvements providing enhanced capabilities and system miniaturization are described.