Alexander Sedunov

DEMON Acoustic Ship Signature Measurements in an Urban Harbor

Detection, classification, and tracking of small vessels are important tasks for improving port security and the security of coastal and offshore operations. Hydroacoustic sensors can be applied for the detection of noise generated by vessels, and this noise can be used for vessel detection, classification, and tracking. This paper presents recent improvements aimed at the measurement and separation of ship DEMON (Detection of Envelope Modulation on Noise) DEMON acoustic signatures in busy harbor conditions. Ship signature measurements were conducted in the Hudson River and NY Harbor. The DEMON spectra demonstrated much better temporal stability compared with the full ship spectra and were measured at distances up to 7 km. The combination of cross-correlation and methods allowed separation of the acoustic signatures of ships in busy urban environments.

Stevens Passive Acoustic System for underwater surveillance

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. The focus of this lab has been the persistent detection and classification of threats posed by surface and subsurface intruders utilizing a multiplicity of technologies. Using these capabilities, we have investigated the set of acoustic parameters fundamental to underwater acoustic threat detection, including diver acoustic signatures, acoustic transmission loss, and acoustic environmental noise. The Stevens Passive Acoustic System has successfully demonstrated surface ship detection and classification. The system provides simultaneous acquisition and analysis of acoustical signals using 4 hydrophones. The analysis functions includes arbitrary digital filtering, spectral analysis and cross-correlation for simultaneous processing of signals from several hydrophones, acoustical source separation, and determination of bearing for different targets relative to the central underwater mooring. The system also records and stores the complete raw acoustical data set, enabling further research and analysis of the acoustic signals. Novel acoustic methods of signal processing used in the system include: 1. Method of precise hydrophone localization. 2. Cross-correlation method for target bearing determination 3. Cross-correlation methods for extraction of target signatures from numerous sources. 4. Feature-based automated diver detection algorithm. 5. Measurements of the ship noise modulation spectrum that is related to propeller and shaft rotation (Detection of Envelope Modulation on Noise — DEMON method). The Stevens Passive Acoustic System has been used in tests in the Hudson River and NY Harbor where a large library of ship acoustic signatures has been collected. Several US Navy sponsored trials demonstrated the ability of the Stevens system for effective diver detection at distances up to 700m.

Concurrent use of satellite imaging and passive acoustics for maritime domain awareness

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. The investigated layers include satellite-based wide area surveillance; HF Radar systems providing over-the-horizon monitoring; and nearshore and harbor passive acoustic surveillance. Integration of these systems is aimed at achieving vessel detection, classification, identification, and tracking. In this paper, we present the results of sea tests where satellite imagery was combined with concurrent passive acoustic surveillance. The wide area sensing was provided by the University of Miami CSTARS facilitys electro-optical (EO) and synthetic aperture radar (SAR) satellite imaging capabilities. Satellites detected the ships using a panchromatic EO sensor FormoSat-2 and SAR from the COSMO-SkyMed constellation. The Stevens Passive Acoustic System was used for detecting sound produced by the same ships that were detected by satellites. Concurrent Satellite — Acoustic measurements provide the following advantages: 1. Increasing the probability of small vessel detection and decreasing false alarms. 2. The joint systems can provide redundant detection and classification in conditions where one of the systems fails. For example, EO satellite imaging does not work at night and in fog and cloudy conditions while acoustic detection has limits during stormy weather due to ambient noise. SAR imaging can detect vessels in all weather, but provides less detail about a specific vessel. 3. Acoustics can provide target classification and bearing and satellites can give target localization and heading. SAR data can be used to estimate vessel speed in some cases. 4. Satellite imaging is helpful for the acoustic detection of an underwater target in cases when satellite information allows separation of surface and underwater targets. 5. Joint measurements provide more data (information) for target classification. Several tests were conducted in New York Harbor, where the satellite images and acoustic signatures of the same boats were recorded. The satellite registered a number of small boats. The small boats were acoustically detected at distances up to 4 km and the signal generated by a passenger ferry was observed at a distance up to 7 km.

Acoustic ship signature measurements by cross-correlation method

Cross-correlation methods were applied for the estimation of the power spectral density and modulation spectrum of underwater noise generated by moving vessels. The cross-correlation of the signal from two hydrophones allows the separation of vessel acoustic signatures in a busy estuary. Experimental data recorded in the Hudson River are used for demonstration that cross-correlation method measured the same ship noise and ship noise modulation spectra as conventional methods. The cross-correlation method was then applied for the separation of the acoustic signatures of two ships present simultaneously. Presented methods can be useful for ship traffic monitoring and small ship classification, even in noisy harbor environments.

Variability of SCUBA diver's acoustic emission

Knowledge of the variability of the acoustic emission characteristics from SCUBA divers is critically important for designing and operating a passive acoustic SCUBA characterization system. Using modeling and experimental measurements in a controlled environment, we identified key source factors influencing the variability of the acoustic emission parameters including Source Band Level (SBL), Spectral Power Density (SPD), and breathing periodicity or emission modulation frequency. The key factors are: equipment, specifically, the design of the first stage (high pressure) regulator and its service life; divers experience and training; and, finally, operating conditions of the equipment and diver, i.e. tank air pressure and the divers motion activity. We found, for example, that the SBL could vary as much as 16 dB depending on the equipment used and up to 15 dB depending on the divers intensity of motion.

Acoustic detection, tracking and classification of Low Flying Aircraft

Low Flying Aircraft (LFA) may be used to smuggle illicit drugs or illegal immigrants across borders. Sound radiated by LFA was used for their detection, tracking and classification by the developed Acousto Seismic Air Detection (ASAD) system. ASAD consists of several nodes, where each node has five microphone clusters and three geophones. Single ASAD node can detect aircraft sound, determine their bearing, and classify the target. Two or mode nodes provide target localization. Extended tests of various small aircraft flying according to planned test patterns were conducted in difficult mountainous areas. The comparison of acoustic detection and tracking with ground truth from the GPS carried by the targets allowed the estimation of acoustic detection, bearing and localization distances and their accuracy.

Towards a passive acoustic underwater system for protecting harbours against intruders

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, small vessels or unmanned underwater vehicles. To increase the level of readiness against underwater threats in harbors, the Netherlands Organization for Applied Scientific Research (TNO) and the Stevens Institute of Technology have recently combined their long-standing expertise on observation systems and sonar technology and are developing an integrated system that can be used to protect harbors from both surface and underwater intruders. In the fall of 2010, TNO and Stevens will initiate joint experiments in a harbour in The Netherlands, where passive acoustic systems from both parties will be combined. In this paper, potential performance of the experimental system is illustrated via simulations. Initial experimental results will be presented at the conference.

Cross‐correlation of ship noise for water traffic monitoring.

Various aspects of the monitoring of ship traffic using correlation of signals recorded by a pair of hydrophones are considered and demonstrated on real signals recorded in the Hudson River. The underwater acoustic noise generated by ships reaches the various hydrophones with a delay depending on their relative positions. That delay can be extracted by cross‐correlation and can serve as a basis for determination of the direction of the ship. This method allowed finding directions for several ships in heavy traffic of Hudson River. The vessel triangulation can be done using information from two or more appropriately located hydrophone pairs. Another application demonstrated is separation of the acoustic signature (noise spectra) from several ships. The last application is the estimation of the ship noise modulation spectrum that is related to propeller and shaft rotation by means of short time cross‐correlation. Comparison with the conventional detection of envelope modulation on noise method shows a close...

Stevens Passive Acoustic system for surface and underwater threat detection

The ability to safeguard domestic shipping and waterside facilities from threats associated with surface and underwater threats (vessels as well as divers) is critical to ensuring security for the maritime domain. Stevens Institute of Technology has been conducting numerous studies and associated field experiments of passive acoustic sensor applications for the detection, characterization, and tracking of surface and underwater threats, which lead to the development of the Stevens Passive Acoustic Detection System (SPADES). The extended diver detection tests were conducted in Newport, Rhode Island and in Den Helder, The Netherlands. Tests involving surface boats were conducted in various locations, including the New York Harbor, Miami, and San Diego. Acoustic tests in Lake Hopatcong, NJ were also conducted in controlled conditions using six distinct boats, including a Panga, a Go Fast boat, a jet ski, and a quiet electrical boat.

Satellite imaging and passive acoustics in layered approach for small boat detection and classification

Emerging technologies to improve the security of ports and inland waterways, as well as coastal and offshore operations, are examined in research being conducted by the Center for Secure and Resilient Maritime Commerce, a Department of Homeland Security National Center of Excellent for Port Security. A layered approach is followed, using above-water and underwater surveillance techniques. High-frequency radar systems providing over-the-horizon monitoring, satellite-based wide-area surveillance, and nearshore and harbor passive acoustic surveillance are included in the investigated layers. A brief review of the Stevens Institute of Technology research in passive acoustics aimed at achieving underwater and surface targets detection, classification, and tracking is presented. The University of Miami Center for Spatial Technologies and Remote Sensing (CSTARS) facilitys electro-optical and synthetic aperture radar satellite imaging provided satellite imagery which was combined with the passive acoustic data. An analysis of the advantages of concurrent use of satellite imagery with passive acoustics for maritime domain awareness is also presented.