Michael Bruno

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.

Feature based passive acoustic detection of underwater threats

Stevens Institute of Technology is performing research aimed at determining the acoustical parameters that are necessary for detecting and classifying underwater threats. This paper specifically addresses the problems of passive acoustic detection of small targets in noisy urban river and harbor environments. We describe experiments to determine the acoustic signatures of these threats and the background acoustic noise. Based on these measurements, we present an algorithm for robustly discriminating threat presence from severe acoustic background noise. Measurements of the targets acoustic radiation signal were conducted in the Hudson River. The acoustic noise in the Hudson River was also recorded for various environmental conditions. A useful discriminating feature can be extracted from the acoustic signal of the threat, calculated by detecting packets of multi-spectral high frequency sound which occur repetitively at low frequency intervals. We use experimental data to show how the feature varies with range between the sensor and the detected underwater threat. We also estimate the effective detection range by evaluating this feature for hydrophone signals, recorded in the river both with and without threat presence.

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.

Cross‐correlation method for measuring ship acoustic signatures.

Stevens Institute of Technology has been conducting research aimed at the development of a low cost passive acoustic system for detection and classification of underwater and surface threats. The system uses several hydrophones where target bearing extraction is carried out by cross correlation of the signal from paired hydrophones. The cross correlation method is constantly being improved by Stevens. This paper presents the recent improvements aimed at the separation and measurements of ship acoustic signatures in busy conditions (when sounds from many ships are received at the same time). The developed method is based on the cross correlation calculation in two different time windows. The relatively large time window (up to 500 ms) is applied for ship bearing detections and full frequency spectra measurements. The short time window (2-5 ms) is used for measurements of detection of envelope modulation on noise acoustic signatures. The new algorithms calculating the modulation spectrum depending on the no...