Barry Bunin

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.

Passive acoustic threat detection in estuarine environments

The Maritime Security Laboratory (MSL) at Stevens Institute of Technology supports research in a range of areas relevant to harbor security, including passive acoustic detection of underwater threats. The difficulties in using passive detection in an urban estuarine environment include intensive and highly irregular ambient noise and the complexity of sound propagation in shallow water. MSL conducted a set of tests in the Hudson River near Manhattan in order to measure the main parameters defining the detection distance of a threat: source level of a scuba diver, transmission loss of acoustic signals, and ambient noise. The source level of the diver was measured by comparing the divers sound with a reference signal from a calibrated emitter placed on his path. Transmission loss was measured by comparing noise levels of passing ships at various points along their routes, where their distance from the hydrophone was calculated with the help of cameras and custom software. The ambient noise in the Hudson River was recorded under varying environmental conditions and amounts of water traffic. The passive sonar equation was then applied to estimate the range of detection. Estimations were done for a subset of the recorded noise levels, and we demonstrated how variations in the noise level, attenuation, and the divers source level influence the effective range of detection. Finally, we provided analytic estimates of how an array improves upon the detection distance calculated by a single hydrophone.

Maritime security laboratory-for maritime security research

Stevens Institute of Technology has established a new Maritime Security Laboratory (MSL) to facilitate advances in methods and technologies relevant to maritime security. MSL is designed to enable system-level experiments and data-driven modeling in the complex environment of an urban tidal estuary. The initial focus of the laboratory is on the threats posed by divers and small craft with hostile intent. The laboratory is, however, evolvable to future threats as yet unidentified. Initially, the laboratory utilizes acoustic, environmental, and video sensors deployed in and around the Hudson River estuary. Experimental data associated with boats and SCUBA divers are collected on a computer deployed on board a boat specifically designed and equipped for these experiments and are remotely transferred to a Visualization Center on campus. Early experiments utilizing this laboratory have gathered data to characterize the relevant parameters of the estuary, acoustic signals produced by divers, and water and air traffic. Hydrophones were deployed to collect data to enable the development of passive acoustic methodologies for maximizing SCUBA diver detection distance. Initial results involving characteristics of the estuary, acoustic signatures of divers, ambient acoustic noise in an urban estuary, and transmission loss of acoustic signals in a wide frequency band are presented. These results can also be used for the characterization of abnormal traffic and improvement of underwater communication in a shallow water estuary.

Long-Wavelength IR Imaging System to Scuba Diver Detection in Three Dimensions

Port surveillance and especially the monitoring of small vessels within a port has been an important focus in port security, whereby today video-based systems are the main candidates for the surveillance despite their apparent inherent limitations at night. This paper presents the results in our experiments in the Hudson River Estuary utilizing a long-wavelength IR imaging system for the detection of a submerged SCUBA diver in three dimensions. During the experiments, the SCUBA diver was in different diving conditions as well as at different depths. Further data analysis shows the correlation of the divers IR signature to the divers depth, which may be used to develop a model to detect the divers depth.

Determination of acoustic attenuation in the Hudson River Estuary by means of ship noise observations

Analysis of sound propagation in a complex urban estuary has application to underwater threat detection systems, underwater communication, and acoustic tomography. One of the most important acoustic parameters, sound attenuation, was analyzed in the Hudson River near Manhattan using measurements of acoustic noise generated by passing ships and recorded by a fixed hydrophone. Analysis of the ship noise level for varying distances allowed estimation of the sound attenuation in the frequency band of 10-80 kHz. The effective attenuation coefficient representing the attenuation loss above cylindrical spreading loss had only slight frequency dependence and can be estimated by the frequency independent value of 0.058 dBm.

Mitigating threats of small vessels to maritime security

This paper discusses technology solutions that may be used to mitigate potential threats and security risks arising from small vessels operating in a busy urban maritime domain such as the New York / New Jersey maritime domain. The solutions focus on persistent surveillance by detecting, tracking, and classifying small vessels, and address the risk posed by these vessels. In a series of experiments conducted in the Hudson River, we collected and analyzed data from various sensors and evaluated several potential technology solutions for detecting these security threats. The threats are addressed across multiple scenarios, ranging from man-made threats to coastal hazards, using assets including radars; acoustic and infrared sensors; vessels and vehicles; and oceanographic and meteorologic prediction tools focused on the water surface, underwater, and urban environments. The results of our experiments show that the combination of sensors provides a valuable means to identify small vessels that may pose a threat in a busy harbor.

On detecting surface and sub-surface bodies in water by virtue of their surface and water column wakes

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 River estuary show that a surface ship wake under some natural illumination conditions has different IR-images in different wave length bands. The carried out analysis of thermal surface wakes demonstrates qualitative and quantitative consistency the Hudson River data with the theoretical estimates. The developed coupled bubble-turbulence wake theory predicts the bubble-wake characteristics versus the wake source parameters. The SIT Towing Tank data demonstrate that the coupled bubble-turbulence theory is reliable. (3) The scuba diver detection is presented by results of experimental study of the wake turbulence, the bubble-wake and its surface manifestations in visual and IR bands in the SIT Towing Tank and the Hudson River. The detection, recognition and tracking in visible and infrared bands of ships and their wakes, and scuba divers, using real-time computer processing are also discussed.

Acoustic research in the Hudson River Estuary at the Stevens Maritime Security Laboratory.

Stevens Institute of Technology has established a Maritime Security Laboratory (MSL) as a national laboratory resource for government, industry, and universities to advance technologies for the protection of USN maritime infrastructure. Experiment instrumentation includes research vessels, a multiplicity of hydrophones and emitters, stand alone acoustic buoys, diver acoustic simulators, unmanned underwater vehicles (UUVs), and precision instrumentation placement capabilities. The in‐river experiments are controlled remotely from a Visualization Center on campus. Acoustic research is supported by sound speed profile measurements, integrated video and acoustic tracking of surface events, and global positionlng system tracking of live divers. Recent results include determination of parameters defining the detection distance of a threat: source level, transmission loss, and ambient noise. The combination of acoustic noise with video data for different kinds of ships in the Hudson River enables estimation of s...

Acoustic noise produced by ship traffic in the Hudson River estuary

This paper presents results of measurements of acoustic noise in Hudson River Estuary near Manhattan in the frequency band 10–100 kHz. The Estuary has very complex sound propagation conditions due to the extremely shallow and high time‐ and space variability of the water characteristics. The acoustic noise was recorded by a set of hydrophones and the acoustic measurements were accompanied by ship traffic video recording using the video‐based Surface Traffic Surveillance system. This video system allowed us to map various boats and ships and to find distances between them and the hydrophone system. The measurements provided acoustic noise data for different kinds of ships in Hudson River, their dependencies on frequencies, and distances. The measurements of noise for various distances were applied for estimation of sound attenuation in a wide frequency band. We calculated the sound attenuation coefficient showing the attenuation loss of an acoustic signal in addition to cylindrically spreading loss. The re...

Estimation of passive acoustic threat detection distances in estuarine environments

The Maritime Secure Laboratory (MSL) at Stevens Institute of Technology supports research in a range of areas relevant to harbor security, including passive acoustic detection of underwater threats. The difficulties in using passive detection in an urban estuarine environment include intensive and highly irregular ambient noise and the complexity of sound propagation in shallow water. MSL measured the main parameters defining the detection distance of a threat: source level of a scuba diver, transmission loss of acoustic signals, and ambient noise. The source level of the diver was measured by comparing the divers sound with a reference signal from a calibrated emitter placed on his path. Transmission loss was measured using the transmission of a sweep signal (1–100 kHz) from the calibrated emitter. The passive sonar equation was then applied to estimate the range of detection. Estimations were done for various recorded noise levels, demonstrating how fluctuations in noise level and the mobility of the diver influence the effective range of detection. Finally, analytic estimates of how a hydrophone array improves upon the detection distance calculated by a single hydrophone are shown. [This work was supported by ONR project No. N00014‐05‐1‐0632: Navy Force Protection Technology Assessment Project.]