Underwater Acoustics

Underwater Acoustics: A Linear Systems Theory Approach is an interdisciplinary and approachable textbook dedicated to the subject of underwater acoustics as well as its applications and research. The book, after giving an introduction and background discussion on underwater topics, covers specific areas such as the fundamentals of linear, space-variant, and time-variant filters; complex apertures; and linear, planar, and volume arrays. Also covered in the book are topics such as signal processing; wave propagation in inhomogeneous media; and random ocean medium transfer functions. Because of its interdisciplinary approach, the text is applicable for students in the fields of electrical engineering, ocean engineering, acoustics, and oceanography who are interested in underwater acoustics and sonar systems engineering.

Contents

Preface

1 Introduction and Background Discussion

1.1 The Propagation of Acoustic Signals in the Ocean

1.2 The Ocean Medium as an Underwater Acoustic

Communication Channel

Bibliography

2 Fundamentals of Linear, Time-Variant, Space-Variant Filters

2.1 Deterministic Filters

2.2 Random Filters

Bibliography

3 Complex Apertures

3.1 Coupling the Transmitted and Received Signals to the Medium

3.2 Directivity Functions

3.3 Linear Apertures and Far-Field Directivity Functions

3.4 Linear Apertures and Near-Field Directivity Functions

3.5 Planar Apertures and Far-Field Directivity Functions

3.6 Planar Apertures and Near-Field Directivity Functions

3.7 Directivity Index

Problems

Bibliography

4 Arrays

4.1 Linear Arrays and Far-Field Directivity Functions

4.2 Linear Arrays and Near-Field Directivity Functions

4.3 Grating Lobes

4.4 Array Gain

4.5 Planar Arrays and Far-Field Directivity Functions

4.6 Planar Arrays and Near-Field Directivity Functions

4.7 Volume Arrays and Far-Field Directivity Functions

Problems

Bibliography

5 Signal Processing

5.1 FFT Beamforming for Planar Arrays

5.2 Complex Envelopes

5.3 The Auto-Ambiguity Function

5.4 Time-Compression-Stretch Factor, Time Delay, and Doppler Shift Expressions

Problems

Bibliography

6 Wave Propagation in Inhomogeneous Media

6.1 The WKB Approximation

6.2 Ray Acoustics

6.3 The Parabolic Equation Approximation

Bibliography

7 Random Ocean Medium Transfer Functions

7.1 Coupling Equations and the Generalized Coherence Function

7.2 The WKB Approximation Revisited

7.3 The Parabolic Equation Approximation Revisited

Bibliography

Answers to Problems

Index