ii
CHARACTERIZATION OF SOUND SPEED PROFILE IN MALAYSIAN SEA
ABDIRAHIM KALIF ALI WARDERE
A project report submitted in partial fulfilment of the
requirements for the award of the degree of
Master of Engineering (Electrical – Electronics & Telecommunication)
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
JANUARY 2013
iii
To My Beloved Parents
To all my beloved siblings (Abdurrahman, Maymun, Abdikarim, Mariam,
Mohammed, Abdullah and Abdulqadir) and in the hope that they will be encouraged
to drive for the best throughout their lifetimes.
And, to all of my teachers and friends who guided and helped me to finish during my
study.
iv
ACKNOWLEDGEMENT
First and foremost, I would like to express my gratitude to ALLAH S.W.T for
guiding me throughout my lifetime and to complete my Master’s project even
thought I have to face many challenges and circumstances. I wish to express my
sincere appreciation to my supervisor, DR. NOR HISHAM BIN HAJI KHAMIS, for
encouragement, advice and guidance. I owe an immense of gratitude to him for his
patient, encouragement, suggestions, believing in my abilities, and careful guidance
was invaluable. It was a great pleasure to me to conduct this thesis under his
supervision.
On this occasion, I would like to take the opportunity to express my
admiration, appreciation and gratitude to my wonderful parents, Khalif Ali Wardere
and Zeinab Abdinur Nuh, who have raised me to be the person who I am today.
Thank them for love, guidance, and support that they have always given me, helping
me to succeed and instilling in me the confidence .I am deeply indebted to them.
A special thanks to my best friends Burhan Omar, Mohamed Abdinur,
Mohamed Omar Halane and Sudi Abdillahi Abdi who help me in this project and for
their support and encouragements, and to all those who gave me the possibilities to
complete my Master.
v
ABSTRACT
The propagation of sound in the sea is dependent on several environmental
factors such as the depth and some other ocean properties. The characteristics of
sound propagation in the sea are determined by the sound speed profile. The sound
speed in the sea is determined and varies with depth, salinity change, temperature,
the season as well as the geographic location. In general, the different sea conditions
have different characteristics of sound speed profile. This project aimed to analyze
the sound speed profile in Malaysian Sea. The data collected from hydrographical
measurement during the Matahari’85 expedition in the South China Sea, in
Terrengganu coastline together with Mackenzie sound speed equation were used to
model the sound speed profile. By comparing the effect of temperature and salinity
on sound speed it was observed that temperature has more effect than salinity. Also
ray tracing model is used to trace the path of sound which travels through the sea
with a sound speed profile given by the depth and corresponding sound speed. In
conclusion, by characterizing sound speed profile in the sea, it enables the prediction
of the direction and the path that the sound propagates.
vi
ABSTRAK
Perambatan gelombang bunyi di dalam laut bergantung kepada beberapa faktor
persekitaran seperti ke dalaman dan ciri-ciri lautan yang lain. Ciri-ciri perambatan
gelombang bunyi adalah ditentukan oleh profil kelajuan bunyi. Halaju bunyi di
dalam lautan adalah ditentukan dan berubah dengan kedalaman, perubahan
kemasinan, suhu, musim dan juga lokasi geografi. Umumnya, keadaan laut yang
berbeza-beza, mempunyai ciri-ciri profil kelajuan bunyi yang berbeza. Projek ini
mensasarkan penganalisaan profil kelajuan bunyi di lautan Malaysia. Data
pengukuran hidrogafi yang dikumpulkan semasa ekspedisi Matahari '85 di Laut
China Selatan bersama dengan persamaan kelajuan bunyi Mackenzie digunakan
untuk menghasilkan model profil kelajuan bunyi. Dengan membandingkan kesan
suhu dengan kemasinan keatas kelajuan bunyi, diperhatikan bahawa suhu
mempunyai lebih kesan terhadap profil kelajuan bunyi. Model Pengesan Sinar juga
digunakan untuk mengesan laluan bunyi yang merambat di lautan berdasarkan profil
kelajuan bunyi yang digunakan bersama kedalaman dan kelajuan bunyi yang
berkaitan. Sebagai kesimpulan, dengan mencirikan profil kelajuan bunyi,
membolehkan ramalan arah dan laluan perambatan gelombang bunyi.
vii
TABLE OF CONTENTS
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGMENT iv
ABSTRACT v
ABSTRAK vi
TABLE OF CONTENTS vii
LIST OF TABLES x
LIST OF FIGURES xi
LIST OF ABBREVIATIONS xiii
LIST OF SYMBOLS xiv
LISR OF APPEDICES xv
1 INTRODUCTIONW
1.1 Introduction 1
1.2 Problem Statement 2
1.3 Project Objectives 2
1.4 Scope of the study 3
1.5 Thesis organization 3
2 BACKGROUND AND LITERATURE REVIEW
2.1 Introduction 5
2.2 Physics of Sound in Water 5
2.3 Properties of sound propagation 7
2.4 Shallow and deep water acoustics 8
viii
2.4.1 Sound propagation in shallow waters 9
2.5 Sound propagation studies 10
2.5.1 Experimental studies 10
2.5.2 Sound propagation modeling 10
2.5.3 The wave Equation 11
2.5.4 Normal Modes 12
2.5.5 Ray Theory 13
2.6 Previous works on sound speed profile 14
2.7 Summary 14
3 SOUND SPEED IN THE SEA
3.1 Introduction 15
3.2 Sound Speed Equations 16
3.2.1 Mackenzie’s Equation 16
3.2.2 Coppens’s Equation 17
3.2.3 The UNESCO Equation: Chen and Millero 17
3.2.4 Del Grosso's Equation 19
3.3 Conversions of pressure and depth 20
3.3.1 Conversion of pressure into depth 20
3.3.2 Conversion of depth into pressure 21
3.4 Sound speed profile 21
3.5 Sound Channel 23
3.5.1 Deep Sound Channel 23
3.5.2 Reliable Acoustic path 24
3.5.3 Surface Duct Propagation 25
3.5.4 Convergence Zone Propagation 26
3.5.5 Bottom Bounce Propagation 27
3.6 The Sound Speed using Signal Processing Concepts 28
3.6.1 Correlation 28
3.6.2 Cross Correlation 28
3.6.3 The flow chart of example in MATLAB form 29
3.6.4 Results of the example 30
3.6.5 Discussion and Conclusion 31
ix
3.6.6 Proofing the assump 31
3.7 Summary 33
4 PROJECT METHODOLOGY
4.1 Introduction 34
4.2 Flow chart 34
4.3 Phase of the Work 35
4.4 Hydrographical Observation in South China Sea 36
4.5 Measurement of physical ocean properties 37
4.6 Parameters of sound speed profiles and their measuring
equipment 39
4.6.1 Temperature 39
4.6.2 Salinity 41
4.6.3 Depth (pressure) 43
4.7 Summary 45
5 RESULTS AND ANALAYSIS
5.1 Results and discussion 46
5.2 Ray tracing method using SSP 50
6 CONCLUSION AND FUTERWORKS
6.1 Conclusion 52
6.2 Suggestion and Recommendation 53
REFERENCES 55
Appendices A – C 58-68
x
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Wave theory versus ray theory 11
3.1 Coefficients of the UNSCO equation: Chen and Millero 18
3.2 Coefficients of the Del Grosso equation 19
4.1 Example of data collected from matahari’85 expedition
and calculated sound speed profile using Mackenzei
Equation
46
xi
LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 Components of a Sound Wave 7
3.1 Typical deep sea SSP 22
3.2 Deep sound channel propagation 23
3.3 Deep source: reliable acoustic path 24
3.4 Critical depths for RAP 24
3.5 Surface duct propagation: shallow source 25
3.6 Surface duct propagation: deeper source 26
3.7 Convergence zone propagation 26
3.8 Bottom bounce propagation 27
3.9 The flow chart of example in MATLAB form 29
3.10 The autocorrelation and cross correlation of input and
output signals. 30
4.1 Project Methodology flow chart 35
4.2 Temperature profiles for station 1, 2 38
4.3 Salinity profiles for station 1, 2 39
4.4 bucket thermometer 40
4.5 Reversing Thermometer for Nansen Bottle 40
4.6 Bathythermograph 41
4.7 Hydrometer 42
4.8 Salinometer 42
4.9 Sounder lead line 43
4.10 Fathometer 44
4.11 Ultrasonic water Depth Meter 44
5.1 Temperature profiles 47
xii
5.2 Salinity profiles 47
5.3 Sound Speed Profiles 48
5.4 Sound Speed Profiles in Salinity 49
5.5 Sound Speed Profiles in Temperature 49
5.6 Ray tracing using Mackenzie equation for sound
speed 51
5.7 Ray tracing using Coppens equation for sound speed. 51
xiii
LIST OF ABBREVIATIONS
CZ - Convergence Zone
DSC - Deep Sound Channel
EEZ - Exclusive Economic Zone
RAP - Reliable Acoustic Path
SCS - South China Sea
SONAR - Sound Navigation And Ranging
SSP - Sound Speed Profile
XBT - Expendable Bathythermograph
xiv
LIST OF SYMBOLS
D - Depth.
dB - Decibel
Hz - Hertz.
Kg/cm2
- Kilogram per centimeter square.
Km2
- Kilometer square.
m - Meter.
m/s or ms-1
- Meter per second.
º C - Centigrade.
ppt - Parts per thousand.
psu - Practical salinity units.
S - Salinity
T - Temperature.
Yd - Yard.
θ - Latitude.
xv
LIST OF APPENDICES
APPENDIX TITLE PAGE
A Data of Matahari’ 85 Expedition and
Calculated Sound Speed By Mackenzie’s and
Coppen’s Equations
58
B MATLAB Simulation Program
Calculating Sound Speed by Mackenzie’s and
Coppen’s Equations
(Using Data of Matahari’ 85 exepedition)
60
C MATLAB Simulation Program
Ray Tracing Model
(Using Sound Speed Profile)
62
CHAPTER 1
INTRODUCTION
1.1 Introduction
The science of production, transmission, reception, and utilization of sound in
the sea is called ocean acoustics. Research and exploratory activities on underwater
life and other resources, communication, sea bottom mapping, and remote control of
equipment etc. utilize sound energy. It is essential in military and rescue operations
and a number of commercial activities like exploration for minerals and oil,
dredging, fisheries, and navigation. Except for a small number of special short-range
applications, frequencies of interest in ocean acoustics are less than a few tens of
kilohertz. This is because sound absorption by sea water increases so much with
frequency that propagation ranges achieved at higher frequencies are very small.
Sonar (originally an acronym for SOund Navigation And Ranging) is one of
popular technique that uses acoustic propagation (usually underwater) to navigate,
communicate with or detect objects on or under the surface of the water, such as
other vessels. Sonar operation is affected by variations in sound speed, particularly in
the vertical plane. Sound travels more slowly in fresh water than in sea water, though
the difference is small. The speed is determined by the water's bulk modulus and
mass density. The bulk modulus is affected by temperature, dissolved impurities
(usually salinity), and pressure. The density effect is small.
2
The largest variation in the speed of sound in water occurs with changes in
depth. Obviously the pressure increases with depth causing a uniform increase of
1.7m/s for every 100m. Furthermore, the ambient temperature changes with depth.
When we plot the speed of sound as a function of depth in the ocean, it is called
sound speed profile. The sound speed profile is a very useful tool for being able to
predict the direction of propagation of sound in the ocean.
1.2 Problem Statement
Underwater communications can be established by transmission of acoustic
waves. Underwater acoustic communications are a rapidly growing field of research
and engineering as the applications, which once were exclusively military, are
extending into commercial fields.
Propagation of acoustic waves faces many problems such as attenuation loss,
absorption loss and delay in acoustic signal. So the need to study sound propagation
and characterize the sound speed profile in seas is very important to underwater
communication.
1.3 Project Objectives
The objectives of this work are:
To investigate the correlation between oceanic variable such as (Temperature,
pressure and salinity) and sound speed profile.
To investigate how sound speed profile effect and control the propagation of
sound in the sea.
To predict the direction and the path of sound waves using the ray tracing
model.
3
1.4 Scope of the Study
The scope of this project is based on a study of underwater acoustic
propagation. The first part of the project consists of the basic theory of sound speed
profile, literature review and environmental studies of profiles such as temperature
profile and salinity profile.
The next part of this project is the simulation of the sound speed profile using
sound speed equations and ray tracing model by MATLAB program.
After performing the simulation we will see how sound speed profiles effect
and control acoustic propagation for shallow water condition.
1.5 Thesis Organization
This thesis is organized into six chapters:
Chapter 1 focuses on introduction, problem definition, research objective and
scope of the work.
Chapter 2 contains the essential background and literature review of the
sound in water and its properties, besides the sound propagation in shallow water and
propagation models.
Chapter 3 presents sound speed and its equations and the parameters that
depend on it such as temperature and salinity; it also contains sound speed profile
and the formation of sound channel in the sea.
4
Chapter 4 describes on project methodology, which provides a full discussion
about the flow of this work. It also contains the hydrographical observation in South
China Sea (Trengganu coastline) and data of salinity, temperature and depth
collected during the expedition of Matahari’85.
Chapter 5 presents the results, result analysis and discussion of the simulation
in chapter 4.
Chapter 6 is the conclusion of overall chapters and future works in the related
area of sound propagation will be discussed. This includes recommendations for
further study.
55
REFERENCES
1. R. J. Urik. Principle of underwater sound. 3th. ed. Peninsula Publishing,
1983.
2. L-3 communication SeaBeam Instruments, Multibeam Sonar theory of
Operation, 2000.
3. C.S. Clay and H. Medwin, Acoustical oceanography: Principles and
applications. New York: Wiley-Interscience, 1977.
4. X. Lurton, "The range-averaged intensity model: A tool for underwater
acoustic field analysis," IEEE j. Oceanic Eng., vol. 17, p. 138, 1992.
5. A. D. Waite. Sonar for Practising engineers. 3th. ed. JOHN WILEY &
SONS, LTD, 2002.
6. G.R.K. Murthy and P.G.K. Murthy, "A case study on the influence of internal
waves on sound propagation in the sea," j. Sound Vib., vol. 108, no. 447,
1986.
7. G.R.K. Murty and M.M. Muni, "A study of some physical properties of
sediments of the backwaters and the adjoining continental shelf off Cochin,
India.," Marine Geology, vol. 76, p. 121, 1987.
8. O. Vijayakumar, "Experimental studies on sound propagation in shallow
waters off the west coast of India.," Indian Institute of Science, August 1989.
9. C.L. Pekeris, "Theory of propagation of explosive sound in shallow water,"
Geol. Soc. Am. Mem, 1948.
10. I. Tolstoy, "Shallow water test of the theory of layered wave guides," j.
Acoust. Soc. Am., vol. 30, p. 348, 1958.
56
11. H.P. Bucker and H.E. Morris, "Normal-mode intensity calculations for a
constant depth shallow water channel," J. Acoust. Soc. Am., vol. 38, p. 1010,
1965.
12. C.B. Officer, Introduction to the theory of sound transmission with
application to the ocean. New York: McGraw-Hill Book Company, 1958.
13. N.R. Chapman and P.D. Ward, "The normal-mode theory of air-to-water
sound transmission in the ocean," J. Acoust.Soc. Am., p. 601, 1990.
14. T. Kitamura and Y. Watanabe, "Direct In Situ Measurements of Sound Speed
Profile and water temperature profiles: The Example of North Lake Biwa," in
SICE annual conference, 2011.
15. Wei Zhang, Yi Wang, Huang, Li Li, and Yang Song, "inversion of sound
speed profile based on waveform structure matching," IEEE. 978-1-4673-
1078-9/11/$26.00, 2011.
16. Fofonoff, N.P. and R.C. Millard, "Algorithms forcomputation of fundamental
properties of sea water," UNESCOTechnical papers in marine science., vol.
46, p. 44, 1984.
17. W.D. Wilson, "equation for the speed of sound in sea water," Acoust. Soc.
Am., vol. 32, p. 1357, 1960.
18. V.A. Del Grosso, "New equation for the speed of sound in natural waters
(with comparisons to other equations).," Acoust. Soc. Am., vol. 56, p. 1084,
1974.
19. C.T. Chen, and F.J. Millero "Speed of sound in sea water at high pressures.,"
Acoust. Soc. Am, vol. 62, p. 1129, 1977.
20. K.V. Mackenzie, "Nine-term equation for sound speed in the oceans.,"
Acoust. Soc. Am., vol. 70, p. 807, 1981.
21. A.B. Coppens, ”Simple equations for the speed of sound in Neptunian
waters,” J. Acoust. Soc. Am. 69(3), pp 862-863, 1981.
57
22. G.S.K. Wong and S Zhu, “Speed of sound in seawater as a function of
salinity, temperature and pressure,” J. Acoust. Soc. Am. 97(3) pp 1732-1736,
1995.
23. C. C. Leroy and F Parthiot, “Depth-pressure relationship in the oceans and
seas” J. Acoust. Soc. Am. 103(3) pp 1346-1352, 1998.
24. Abu Khair Mohammad Mohsin, Mohd. Ibrahim Hj. Mohamed, Mohd. Zaki
Mohd Said, Ekspedisi matahari 89 a study on the offshore waters of the
Malaysian EEZ.: Universiti Pertanian Malaysia, Serdang Faculty of Fisheries
and Marine, 1990.
25. Abu Khair Mohammad Mohsin, Mohd. Ibrahim Hj. Mohamed, Mohd. Azmi
Ambak, Ekspedisi matahari 85 a study on the offshore waters of the
Malaysian EEZ.: Universiti Pertanian Malaysia, Serdang Faculty of Fisheries
and Marine, 1986.
26. P.M. Sivalingam, "Chemical Oceanography observation of the South China
Sea," Sains Malaysiana, pp. 139-154, 1977.
27. http://www.marinebio.net/marinescience/01intro/tosamp.htm
