Marine Acoustics Short Course - Course Topics

Fundamentals of Acoustics: A review of basic vibration theory, basic acoustic theory, and the physics of sound propagation, reflection, and absorption phenomena. 

Sonar Concepts Overview: This section will provide a detailed overview of the active and passive sonar equations as well as a discussion of the individual components in these sonar equations in terms of the relevant physics and system parameters.   

Introduction to Propagation: Introduction to acoustic propagation theory and modeling in the ocean environment including selected experimental results and comparison to theory.  Various propagation theories and examples will be discussed including ray theory, mode theory, and the parabolic equation. 

Overview of Scattering, Reverberation and Ambient Noise: Overview of scattering, reverberation, and ambient noise theory and experimental results. Models for scattering, reverberation, and ambient noise will be introduced as part of this topic. 

Introduction to the Representation and Processing of Signals in Space and Time: This section will introduce the basic signal processing framework that maps signals from their representation via solutions to the acoustic propagation equations to a simplified representation suitable for developing and analyzing signal processing algorithms.  Representations of the signals via the spatial frequency  (i.e., the wavenumber) and signal replica vector will be covered with a particular emphasis on the physical insights gained from Fourier analysis.  The spatial sampling of signals at arrays of sensors will be introduced along with the concepts of spatial  aliasing.  Spatial filtering via linear beamforming will be introduced along with the concepts of spatial resolution, interference rejection and processor robustness.  The traditional and correlated-noise matched filters will also be introduced.

Introduction to Detection, Classification, Localization and Tracking:  Introduction to the basic functional elements of sonar signal processing:  localization, detection, tracking and classification.  The objective, relevant performance measures, design approach, practical aspects, and key concepts of each area are covered through theory and examples from active and passive sonar applications.

Advanced Detection Concepts: This section covers the detection problem in more detail.  The detection-threshold term in the sonar equation is related to detector performance for common scenarios.  The process of detector design through signal and noise characterization and hypothesis testing is presented for both signals with known form (matched filter detector) and signals with unknown form (energy detector).  Also covered are practical aspects of detection such as normalization, Doppler filter banks, and estimating detection performance.

Marine Bioacoustics: Provides an introduction to the role of active and passive acoustic technology in studying organisms in the marine environment. Topics include marine animal hearing, marine animal acoustic communication, remote sensing, and the impacts of sound on marine animals.

Marine Acoustic Remote Sensing: Introduction to the application of acoustics in the study of the undersea environment and an overview of the concepts and systems used for making underwater measurements. Specific topics include the use of acoustics as a tool in oceanographic instrumentation, the use of acoustics in the study of ocean processes, and current issues in ocean acoustics research.

Underwater Acoustic Communications: This section will cover the transmission, reception and processing of acoustic communications signals in realistic ocean environments.  It will describe the common methods of encoding information on acoustic signals as well as the processing methods by which the information is extracted from the received signals.  Both adaptive and non-adaptive techniques will be covered.  The impact of different environmental processes on communications system performance will be investigated as will methods of modeling and predicting the performance of underwater acoustic communications systems.

Target Scattering: Understanding the echo formation process is central to the design and operation of effective active sonar systems. This session explores the principal scattering mechanisms and how they encode information in the echo that can be exploited for detection, classification, and tracking. Content includes discussion of the process of echo formation, target strength definition and measurement, scattering from simple and complex shapes, elastic effects, and simulation modeling techniques.

Transducer Materials and Devices: Principles of transduction and sonar transducer design; electromechanical analog circuits; frequency response characteristics; coupling coefficient; efficiency; directivity characteristics of receivers; transducer measurement techniques; discussion of calibration facilities.

Imaging Sonar: The imaging session will provide an overview of a number of imaging modalities including forward looking, sidescan, and synthetic aperture sonar. This session will establish the similarities between these modalities and describe the differences in the imagery products generated from each type of sonar.

Array Concepts: This section will cover an array of topics (pun intended);  the physical geometry of arrays:  linear, planar, cylindrical, spherical, annular, waveguide, elliptical, etc.;  amplitude and phase/time delay shading affects for 1D, 2D, and 3D arrays;  effects of baffle and backing conditions;  effects of channel to channel phase and gain variances on directivity and SONAR performance; resonance vs. non-resonance transduction trades for transmitter, receiver, and transmitter/receiver array performance optimization;  transducer and electronics noise considerations;  design considerations for a range of frequencies (100 Hz to 2 MHz); and near-field versus far-field directivity.

Demonstrations in Acoustics and Signal Processing: Demonstrations related to course material in transduction, acoustic propagation, and signal processing. Transducer characteristics; beamforming and array performance; parametric arrays; waveguide propagation; reflection from smooth and rough surfaces; target scattering; frequency domain processing; matched filtering and signal detection.