Page 377 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

Underwater Acoustics
CHAPTER CONTENTS
14
14.1 Introduction................................................................................................................................370
14.2 Sound propagation......................................................................................................................370
14.2.1 Pressure..............................................................................................................370
14.2.2 Intensity..............................................................................................................371
14.2.3 Decibel................................................................................................................372
14.2.4 Transmission loss ................................................................................................. 372 14.2.4.1 Geometricalspreading....................................................................................372 14.2.4.2 Absorption loss............................................................................................... 373 14.2.4.3 One-waytransmissionloss..............................................................................374
14.3 Transducers................................................................................................................................374
14.3.1 Construction........................................................................................................374
14.3.2 Efficiency............................................................................................................374
14.3.3 Transducer bandwidth........................................................................................... 375
14.3.4 Beampattern.......................................................................................................375
14.3.5 Directivityindex...................................................................................................377
14.3.6 Transmittingresponse...........................................................................................378
14.3.7 Sourcelevel.........................................................................................................379
14.3.8 Medium beam/narrow beam transducer .................................................................. 380
14.4 Acoustic noise............................................................................................................................380
14.4.1 Environmental ...................................................................................................... 380
14.4.2 Noise level calculations ........................................................................................ 380
14.4.3 Thrusternoise......................................................................................................381
14.4.4 Sound paths ........................................................................................................ 381
14.4.5 Sound velocity ..................................................................................................... 381
14.4.6 Reflections..........................................................................................................383
Mathematics is the language of science. All of the properties of underwater acoustics can be expressed in mathematical terms. Later in this chapter, as well as in Chapter 15 on sonar, two of the practical applications of underwater acoustics (acoustic positioning and imaging/profiling sonar) will be explored. In the initial sections of this chapter, the theoretical basis of underwater acoustics is presented to segue into the acoustic positioning and sonar applications.
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© 2014 Robert D Christ and Robert L Wernli. Published by Elsevier Ltd. All rights reserved.
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