Engineering and the Environment, University of Southampton

Knowledge and understanding
Having successfully completed the module, you will be able to demonstrate knowledge and understanding of:

• How to employ the sonar equations, to model and assess the performance of sonar systems.
• The trade-offs involved when designing a sonar system.
• Elementary modelling of acoustic scattering: as it affects both acoustic targets and volume reverberation.
• The range of propagation models available.
• Ray tracing methods in a range independent, deep water, context and in shallow water through the use of the method of images.
• Normal mode methods for shallow water propagation modelling, assuming simple boundary conditions.
• The transduction mechanisms in marine mammals.
• The role of underwater acoustics in the protection of marine mammals.

Cognitive (thinking) skills
Having successfully completed the module, you will be able to:

• Read, understand and interpret the literature relating to underwater acoustics.

Practical, subject specific skills
Having sucessfully completed the module, you will be able to:

• Undergo a paper design of a sonar system in an idealised scenario.
• To select an appropriate propagation model.
• To advise on the construction of an EIA from underwater noise.

Key transferable skills
Having successfully completed the module, you will be better able to:

• Understand the issues associated with acoustic modelling in general.
• Appreciate system design issues.
• Comprehend the basics of the need to assess environmental impacts.

The aims of this module are to:

• To provide an overview of mathematical techniques used in sonar system modelling and to provide an appreciation of the potential impact of sonar systems on marine mammals.

• To provide a summary of sonar system performance evaluation techniques, through the “sonar equations”.
• To offer a basic understanding of the principles of simple acoustic propagation models.
• To provide an overview of how marine mammals employ sonar and to understand how human noise can impact on them.

The Sonar Equations

• Classes of sonar systems: Active/Passive, Monostatic/Bistatic.
• Definitions of the basic terms within the sonar equations.
• Signal detection criteria.
• Derivation of the passive sonar equation
• Derivation of the active (noise-limited) sonar equations.

Noise Level Calculations

• Noise spectral level.
• Bandwidth.
• The effects of Doppler shifts.

Transmission Loss

• Simple models for geometric losses.
• Transmission loss due to absorption.

Target Strength Calculations

• Geometric scattering from a sphere.
• Rayleigh scattering from a sphere.
• Resonant scattering from a sphere.

Volume Reverberation

• The reverberation limit.
• Calculation of volume reverberation level.
• The transition between reverberation and noise limited operations.

Directivity Index Calculation

• Directivity of a uniform line array at the design frequency.
• Approximation for the directivity of a uniform line array at frequencies away from the design frequency.

Classes of Acoustic Propagation Models

• Range dependent vs range independent.
• 2-D and 3-D models.

Ray Tracing

• The eikonal and transport equations
• Snell’s law as obtained through the eikonal equation.
• Travel times and distances travelled along rays.
• Transmission loss along a ray.
• Focusing factors, shadow zones and caustics.
• Practical implementation of ray tracing models.

Method of Images

• General expression for shallow water, isospeed propagation.
• Specific solutions for various bottom conditions.

Method of Normal Modes

• Model solution of the wave equation, in a sound channel.
• Truncation of the modal series.
• Phase and group velocities of modes.
• Comparison with method of images solution.

Bioacoustics

• Marine mammal vocalizations.
• Hearing in marine mammals.
• Sound Production in Cetaceans.
• Human impact on marine mammals.

2 lectures a week.

Working on examples provided to students in order to practise their analytical skills. Students are encouraged to read supporting texts and a booklist is provided, along with links to dedicated websites.

Secondary text

Principles of Underwater Sound
3rd Edition, 1983
2nd Edition, 1975
1st Edition, 1967 (Appeared as: Principles of Underwater Sound for Engineers), R J Urick, McGraw Hill
007066087

Ocean Acoustics: Theory and Experiment in Underwater Sound
1st Edition, 1966
2nd Edition, 1987, I Tolstoy

C S Clay, McGraw Hill

(No ISBN)
0070649413

Acoustical Oceanography: Principles and Applications
1st Edition, 1977, C S Clay
H Medwin, Wiley
0471160415

Fundamentals of Acoustical Oceanography
1st Edition, 1997, C S Clay
H Medwin, Academic Press
012487570

Fundamentals of Ocean Acoustics
1st Edition, 1982
2nd Edition, 1991
, L M Brekhovskikh
P Lysanov Yu., Springer Verlag
0387529764
3540113053

Underwater Acoustic System Analysis
1st Edition, 1984
2nd Edition, 1991, W S Burdic, Prentice Hall

0139476075

Underwater Acoustics Systems, 1990, F G W Coates, Macmillan
0333425421

Fundamentals of Acoustics
2nd Edition 1962
3rd Edition 1982, L E Kinsler
A R Frey et al, Wiley

0471029335

Computational Ocean Acoustics
2nd Edition, 2000, W Kuperman
F Jensen
H Schmidt
M Porter, American Institute of Physics
1563962098

Marine Mammals and Noise, W Richardson
C R Greene
C I Malme
D H Thompson, Academic Press
0125884419