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The Stevens Passive Acoustic System allows the detection, tracking and classification of various surface and underwater sources of sound including surface vessels, swimmers, various types of divers, and unmanned underwater vehicles. This system was developed by Stevens in its Maritime Security Laboratory, which was established to support research in the area of Anti-Terrorism and Force Protection...
This paper presents theoretical and experimental results of detection and parameterization of moving bodies and scuba divers based on their surface and water column signatures under Hudson River estuary conditions. (1) Theoretical and experimental (SIT DL Towing Tank) estimates of wake characteristics for bodies of interest are carried out. (2) The IR-images of ship wakes at the surface of the Hudson...
The research being conducted in the Center for Secure and Resilient Maritime Commerce (CSR), a DHS National Center of Excellence for Port Security examines some basic science issues and emerging technologies to improve the security of ports and inland waterways, as well as coastal and offshore operations. This research follows a layered approach utilizing above water and underwater surveillance techniques...
One of the most challenging aspects of port security is to provide protection against surface and underwater threats. In particular, a significant terrorist threat might be posed to the domestic harbors in the form of an explosive device delivered underwater by a scuba diver. Along with improving swimmer detection technology, the question arises of how to respond to underwater swimmer threats once...
The international rules for the protection of harbors against threats and intruders typically apply to threats emanating from the land side. Protection against actions and threats from the water side is much less regulated, apart from some individual cases. Potential threats from the water side may consist of intruders including divers with and without delivery vehicles, swimmers, small submarines,...
This paper considers the problem of passive acoustic detection of a diver in a shallow water environment. A frequency- domain multi-band matched-filter approach to swimmer detection is presented. The idea is to break the frequency contents of the hydrophone signals into multiple narrow frequency bands, followed by time averaged (about half of a second) energy calculation over each band. Then, spectra...
Time reversal acoustics (TRA) provides a way to focus ultrasound in space and time. Standard TRA focusing system produces tone burst signal with a frequency band limited by the bandwidth of the transducer. For certain medical applications, both in therapy and imaging, a wider bandwidth is required. The goal of this study was to explore a possibility to generate shorter pulses less affected by the...
This paper describes an algorithm for the automatic detection of a particular class of underwater sounds, using a single hydrophone. It is observed that many life-forms, systems or mechanisms emit distinctive acoustic signatures which are characterized by packets of relatively high frequency sound that are repeated at regular, low frequency intervals. These types of sounds are commonly produced by...
The ultrasound focusing systems based on time reversal acoustic (TRA) principles are capable of delivering ultrasound energy to the specific region in a highly inhomogeneous medium with focusing efficacy virtually unachievable using conventional phased array transmitters. Furthermore, numerous reflections from various boundaries, which distort focusing in conventional ultrasound focusing systems and...
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