Sonar Principles and ASW Analysis

This three-day course provides an excellent introduction to underwater sound and highlights how sonar principles are employed in ASW analyses. The course provides a solid understanding of the sonar equation and discusses in-depth propagation loss, target strength, reverberation, arrays, array gain, and detection of signals. Physical insight and typical results are provided to help understand each term of the sonar equation. The instructors then show how the sonar equation can be used to perform ASW analysis and predict the performance of passive and active sonar systems. The course also reviews the rationale behind current weapons and sensor systems and discusses directions for research in response to the quieting of submarine signatures. The course is valuable to engineers and scientists who are entering the field or as a review for employees who want a system level overview. The lectures provide the knowledge and perspective needed to understand recent developments in underwater acoustics and in ASW. A comprehensive set of notes and the textbook Principles of Underwater Sound will be provided to all attendees.

• Sonar parameters and their utility in ASW Analysis.
• Sonar equation as it applies to active and passive systems.
• Fundamentals of array configurations, beamforming, and signal detectability.
• Rationale behind the design of passive and active sonar systems.
• Theory and applications of current weapons and sensors, plus future directions.
• The implications and counters to the quieting of the target’s signature.

1. Sonar Equation & Signal Detection. Sonar concepts and units. The sonar equation. Typical active and passive sonar parameters. Signal detection, probability of detection/false alarm. ROC curves and detection threshold.
2. Propagation of Sound in the Sea. Oceanographic basis of propagation, convergence zones, surface ducts, sound channels, surface and bottom losses.
3. Target Strength and Reverberation. Scattering phenomena and submarine strength. Bottom, surface, and volume reverberation mechanisms. Methods for modeling reverberations.
4. Arrays and Beamforming. Directivity and array gain; sidelobe control, array patterns and beamforming for passive bottom, hull mounted, and sonobuoy sensors; calculation of array gain in directional noise.
5. Passive Sonar. Illustrations of passive sonars including sonobuoys, towed array systems, and submarine sonar. Considerations for passive sonar systems, including radiated source level, sources of background noise, and self noise.
6. Active Sonar. Design factors for active sonar systems including transducer, waveform selection, and optimum frequency; examples include ASW sonar, sidescan sonar, and torpedo sonar.

Dr. Nicholas C. Nicholas received a B. S. degree from Carnegie-Mellon University, an M.S. degree from Drexel University, and a PhD degree in physics from the Catholic University of America. His dissertation was on the propagatior of sound in the deep ocean. He has been teaching underwater acoustics courses since 1977 and has been visiting lecturer at the U.S. Naval War College and several universities. Dr. Nicholas has more than 35 years experience in underwater acoustics and submarine related work. Dr. Nicholas is currently consulting for several firms.

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