Using Acoustic Emission Technique with Matlab® Analysis to Detect Termites in Timber-in-Service

305 Pages·2017·16.77 MB·English

Using Acoustic Emission Technique
with Matlab® Analysis to Detect Termites
in Timber-in-Service

Ahmed El-Hadad

(ORCID ID 0000-0003-4996-1374)

Submitted in total fulfilment of the requirements of the degree of
Doctor of Philosophy

November 2017

School of Ecosystem and Forest Sciences
Faculty of Science

The University of Melbourne
Abstract

Termites are important to the environment, yet, they cause extensive damage to
wooden structures in Australia and world-wide. Most of the termite damage inflicted
to structural timber is caused by subterranean termites. Termite damage could be
considerably reduced through improved early detection of termite infestations in
building structures. It is more beneficial to develop nondestructive termite detection
methods to protect timber-in-service than to repair damage caused by termite
infestations.

Conventional methods of locating and identifying termites are mainly based on visual
inspection technique which is neither accurate nor reliable. Hence, the main purpose
of this research was to examine a nondestructive acoustic technology that could detect
and locate termites in timber-in-service based on their ecological and biological
behaviour. The proposed termite detection technique was designed to detect termites
based on a number of factors such as infestation area temperature and moisture,
termite movement, foraging behaviour, feeding and possibly by means of sensing the
communication between foraging termites.

An acoustic technique was used to test termite feeding and alarming sounds. The
main factors considered during the experiments were: infested timber type, timber
grain orientation, timber moisture content, the distance between termite feeding sites
and the recording microphones and the number and caste of termites foraging and
feeding on the timber.

The findings of this research revealed that there was a small difference or distinction
between the sound generated by termite activities and the external interfering sound
within the timber. The main challenge in the research was to filter the termite activity
sound from background noises. It was possible to achieve this by analysing the
frequency and time domains of the recorded signals and studying their sound
characteristics.

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The findings pointed to different factors that affected the travelling Acoustic Emission
(AE) signals through the wood. These factors were mainly: the wood type, moisture
content (MC) level, the signal’s travelling distance and orientation of the travelling
signal through the wood. All experimental results showed that termite AE signals,
which were generated due to termite infestations in wood, could be detected using AE
detectors.

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Declaration

This is to certify that the thesis comprises only my original work towards
the PhD. Due acknowledgement has been made in the text to all other
materials used. The thesis is fewer than 100,000 words in length, exclusive
of tables, maps, bibliographies and appendices.

Signature
………………………….……

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Acknowledgments

First, I praise God, Allah the Almighty, for granting me this opportunity and providing
me with the capability to carry out this research. This thesis would not have come into
existence without His will and support.

I would like to express my sincere gratitude and appreciation to my supervisors, Dr
Berhan Ahmed, Associate Professor Graham Ian Brodie and Associate Professor Peter
Farrell, and to the Head of my Advisory Committee, Professor Barbara Ozarska, for
their continuous support of my PhD research. I appreciate their patience, motivation
and extensive knowledge, which they generously shared with me throughout this
journey. They have been remarkable mentors for me and their ongoing guidance has
been invaluable to both my research and career.

I would also like to thank my Advisory Committee members: Professor Bill Moran,
Associate Professor Allison Kealy and Dr Sofia Suvorova for their constructive advice
concerning the progress of my research.

Special thanks go to Dr John French for his assistance in the area of termite detection
during our fieldtrips to Gove in the Northern Territory and for his support and valuable
advice following the above trips. I am also appreciative to Dr Denise Johnstone for her
assistance in using the PICUS® Sonic Tomograph device, to Mr Mark Nan Tie (Citipower
and Powercor Australia, Environmental Manager) for facilitating access to power poles
and providing the required power pole data and to Mr Tom Boschma (Specialist
Termite Control, Director) for facilitating visits to his customers during termite
detection processes, which was helpful in running AE research experiments on the
discovered termite nests.

I also wish to acknowledge Dr Diane Brown for copyediting the thesis according to the
Australian Standards for Editing Practice (2013) and national IPED/DDOGS guidelines
for editing/proofreading theses.

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Words cannot express my gratitude to my mother, father and sister. Their support and
prayers have sustained me thus far. I would also like to thank all of my friends and
colleagues whose encouragement helped me strive towards my goal.

I wish to conclude by expressing my special appreciation and thanks to my beloved
wife for her support, morally and practically, throughout this journey and the writing
of my thesis. She has always been my support in every milestone I achieved.

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Table of Contents

1 INTRODUCTION ............................................................................................................................ 7
1.1 TERMITE BACKGROUND ........................................................................................................................ 7
1.2 TERMITE ECONOMIC IMPORTANCE ......................................................................................................... 7
1.3 TERMITE BIOLOGY AND ECOLOGY ........................................................................................................... 9
1.3.1 Description ............................................................................................................................ 9
1.3.2 Relationship to other insects ................................................................................................ 9
1.3.3 Castes.................................................................................................................................. 10
1.3.4 Feeding ............................................................................................................................... 12
1.3.5 Foraging .............................................................................................................................. 14
1.3.6 Nest types ........................................................................................................................... 15
1.3.7 Classification of termites .................................................................................................... 16
1.3.8 Termite ecology .................................................................................................................. 18
1.3.9 Decay and fungi .................................................................................................................. 18
1.4 TERMITE DETECTION TECHNIQUES ........................................................................................................ 20
1.4.1 Expected Criteria for Termite Detection System ................................................................. 20
1.4.2 Choosing Acoustic Emission (AE) as the field of research ................................................... 21
1.5 AIM OF THIS THESIS ........................................................................................................................... 21
1.6 RESEARCH QUESTIONS ....................................................................................................................... 22
1.6.1 RQ1 ..................................................................................................................................... 22
1.6.2 RQ2 ..................................................................................................................................... 22
1.7 RESEARCH HYPOTHESIS ...................................................................................................................... 22
1.8 IMPORTANCE OF THIS STUDY ............................................................................................................... 22
1.9 STUDY SCOPE AND LIMITATIONS .......................................................................................................... 23
1.10 EQUIPMENT AND APPLICATIONS USED IN THE THESIS EXPERIMENTS ........................................................ 23
1.11 THESIS STRUCTURE ....................................................................................................................... 24
2 LITERATURE REVIEW ................................................................................................................... 28
2.1 CURRENT TERMITE DETECTION TECHNIQUES .......................................................................................... 28
2.1.1 Locating termite damage ................................................................................................... 28
2.1.2 Traditional (non-technological) termite control techniques ............................................... 30
2.1.3 Technological termite control techniques ........................................................................... 33
2.2 WOOD PROPERTIES ........................................................................................................................... 45
2.2.1 Wood categories ................................................................................................................. 46
2.2.2 Structure of wood ............................................................................................................... 46
2.2.3 Hardwood and Softwood .................................................................................................... 47
2.2.4 Dielectric properties and conductivity of wood .................................................................. 49
2.2.5 Wood moisture effect ......................................................................................................... 50
2.3 ACOUSTIC EMISSION (AE) .................................................................................................................. 51
2.3.1 Selecting AE as Termite Detection Method ........................................................................ 52
2.3.2 AE Limitations ..................................................................................................................... 52
2.4 ACOUSTIC PROPERTIES OF WOOD ........................................................................................................ 53
2.5 FOURIER TRANSFORM ........................................................................................................................ 54
2.6 SIGNAL PROCESSING AND FILTER DESIGNING .......................................................................................... 56
2.6.1 Signal processing ................................................................................................................ 56
2.6.2 Signal filtering ..................................................................................................................... 56
2.6.3 Designing filters using Matlab® .......................................................................................... 58
3 SOUND-WOOD INTERACTION ..................................................................................................... 59
3.1 ACOUSTIC EMISSION TECHNOLOGY AND SOUND-WOOD INTERACTION ........................................................ 59
3.2 EXPERIMENT 1: PRELIMINARY EXPERIMENT ............................................................................................ 62
3.2.1 Introduction ........................................................................................................................ 62
3.2.2 Method ............................................................................................................................... 63
3.2.3 Results................................................................................................................................. 66
3.2.4 Discussion ........................................................................................................................... 67
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3.2.5 Conclusion ........................................................................................................................... 68
3.3 EXPERIMENT 2: SECONDARY SOUND EXPERIMENT IN WOOD USING SOUND RECORDINGS ............................... 69
3.3.1 Introduction ........................................................................................................................ 69
3.3.2 Method ............................................................................................................................... 70
3.3.3 Secondary experiment stage-1 ........................................................................................... 73
3.3.4 Secondary experiment stage-2 ........................................................................................... 73
3.3.5 Results................................................................................................................................. 74
3.3.6 Discussion ........................................................................................................................... 78
4 LABORATORY TECHNIQUE ON TERMITE SOUND DETECTION ...................................................... 79
4.1 EXPERIMENT 3: LABORATORY ANALYSIS OF TERMITE ACTIVITIES IN WOODEN BLOCKS .................................... 83
4.1.1 Introduction ........................................................................................................................ 83
4.1.2 Method ............................................................................................................................... 83
4.1.3 Results................................................................................................................................. 86
4.1.4 Discussion ........................................................................................................................... 88
4.1.5 Conclusion ........................................................................................................................... 89
4.2 EXPERIMENT 4: LABORATORY ANALYSIS OF TERMITE ACTIVITIES IN WOODEN STAKES..................................... 89
4.2.1 Experiment 4.1: Termites-in-Stakes experiment ................................................................. 89
4.2.2 Experiment 4.2: Stakes-in-Box experiment ......................................................................... 93
5 FIELD STUDY ON TERMITE SOUND DETECTION ........................................................................... 98
5.1 EXPERIMENT 5: TERMITE SOUND DETECTION IN TREES AND WOODEN STRUCTURES ...................................... 98
5.1.1 Sound detection in trees ..................................................................................................... 98
5.1.2 Sound detection in wooden structures ............................................................................... 99
5.1.3 Experiment 5.1: Eltham North Experiment ....................................................................... 100
5.1.4 Experiment 5.2: Ivanhoe Experiment ................................................................................ 106
5.2 EXPERIMENT 6: TERMITE SOUND DETECTION IN POWER POLES ................................................................ 109
5.2.1 Experiment 6.1: Power Pole Sound Test ........................................................................... 110
5.2.2 Experiment 6.2: Horsham & Stawell Experiments ............................................................ 113
6 DISCUSSION AND CONCLUSION ................................................................................................ 117
6.1 RESEARCH SCOPE AND LIMITATIONS ................................................................................................... 118
6.2 ANALYSIS OF RESEARCH CONCLUSION ................................................................................................. 118
6.3 RESEARCH CONCLUSIONS .................................................................................................................. 120
6.3.1 Conclusions relating to Sound-Wood interaction ............................................................. 120
6.3.2 Conclusions relating to termite AE signals ........................................................................ 121
6.4 CONCEPTUALISATION OF AE TERMITE DETECTION SYSTEM ...................................................................... 122
6.5 RESEARCH NOVELTY AND CONTRIBUTION TO SCIENCE ............................................................................ 123
6.6 RECOMMENDATIONS AND FURTHER INVESTIGATION .............................................................................. 123
7 REFERENCES.............................................................................................................................. 125
8 APPENDICES ............................................................................................................................. 148
APPENDIX-A (SAMPLE OF EXPERIMENT RESULTS) .............................................................................. 148
Experiment 1: Preliminary experiment ............................................................................................ 148
Experiment 2: Secondary sound experiment ................................................................................... 160
Experiment 3: Laboratory analysis of Termite activities in wooden blocks .................................... 196
Experiment 4: Laboratory analysis of Termite activities in wooden stakes .................................... 210
Experiment 5: Termite sound detection in trees and wooden structures ....................................... 236
Experiment 6: Termite sound detection in power poles .................................................................. 267
APPENDIX-B (MATLAB® CODES) ......................................................................................................... 287
Experiment 1 ................................................................................................................................... 287
Experiment 2 ................................................................................................................................... 288
Experiment 4 ................................................................................................................................... 294
Experiment 5 ................................................................................................................................... 296
Experiment 6 ................................................................................................................................... 297

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List of Figures

FIGURE ‎1.1: CASTES OF COPTOTERMES ACINACIFORMIS, RHINOTERMITIDAE: ............................................ 10
FIGURE ‎1.2: MOUND OF A GRASS-FEEDER TERMITE (AMITERMES LAURENSIS) IN GOVE, NORTHERN TERRITORY,
AUSTRALIA ............................................................................................................................. 16
FIGURE ‎2.1: SAMPLES OF TIMBER-IN-SERVICE DAMAGED BY TERMITE AND DECAY FUNGI ............................. 29
FIGURE ‎2.2: THERMAL IMAGING ........................................................................................................ 35
FIGURE ‎2.3: PICUS® SENSORS .......................................................................................................... 38
FIGURE ‎2.4: PICUS® TEST ................................................................................................................ 38
FIGURE ‎2.5: TERMATRAC TERMITE DETECTOR ....................................................................................... 41
FIGURE ‎2.6: DIFFERENT TYPES OF THE MOISTURE METERS ...................................................................... 44
FIGURE ‎2.7: TDS GAS DETECTOR ........................................................................................................ 45
FIGURE 2.8: WOOD STRUCTURE ........................................................................................................ 49
FIGURE ‎2.9: SQUARE WAVE ............................................................................................................... 55
FIGURE ‎2.10: BAND PASS FILTER (BPF) DESIGN ................................................................................... 57
FIGURE ‎2.11: BAND PASS FILTER CUT-OFF FREQUENCIES ........................................................................ 58
FIGURE 3.1: PRELIMINARY EXPERIMENT SETUP SHOWS THE SIGNAL GENERATOR SENT A SQUARE WAVE SIGNAL
THROUGH THE WOOD SAMPLE ALONG THE GRAIN AND DISPLAYED ON THE OSCILLOSCOPE SCREEN ......... 63
FIGURE 3.2: PRELIMINARY EXPERIMENT WOOD SAMPLES ....................................................................... 65
FIGURE 3.3: FOUR SOFTWOOD SAMPLE STAKES .................................................................................... 70
FIGURE 3.4: SECONDARY SOUND EXPERIMENT SETUP ............................................................................ 71
FIGURE ‎4.1: LABORATORY TERMITE ACTIVITIES IN WOODEN BLOCKS ......................................................... 83
FIGURE ‎4.2: ORIGINAL UNFILTERED INPUT SIGNAL RECORDED DISPLAYED BY COOL EDIT PRO 2.1 © .............. 84
FIGURE ‎4.3: BPF1 WHICH PASSES 3000-5500HZ FREQUENCY BAND DESIGNED BY COOL EDIT PRO 2.1 © .... 85
FIGURE ‎4.4: RESULT SIGNAL AFTER APPLYING BPF1 DISPLAYED BY COOL EDIT PRO 2.1 © ........................... 85
FIGURE ‎4.5: BPF2 WHICH PASSES 3500-5000HZ FREQUENCY BAND DESIGNED BY COOL EDIT PRO 2.1 © .... 86
FIGURE ‎4.6: OUTPUT SIGNAL AFTER APPLYING BPF1 DISPLAYED BY COOL EDIT PRO 2.1 © ......................... 86
FIGURE ‎4.7: TERMITES-IN-STAKES EXPERIMENT .................................................................................... 90
FIGURE ‎4.8: STAKES-IN-BOX EXPERIMENT SETUP .................................................................................. 94
FIGURE ‎5.1: ELTHAM NORTH EXPERIMENT ........................................................................................ 101
FIGURE ‎5.2: PORTABLE CAMERA, WITH ATTACHED THREE MICROPHONES USED IN ELTHAM NORTH EXPERIMENT
.......................................................................................................................................... 102
FIGURE ‎5.3: BAND PASS FILTER (BPF) OF 3 TO 4.5KHZ PASS BAND ....................................................... 103
FIGURE ‎5.4: FILTERED SIGNAL AFTER APPLYING BPF OF 3 TO 4.5KHZ PASS BAND ..................................... 103
FIGURE ‎5.5: TERMITE TRAILS IN THE EXTRACTED SIGNAL DISPLAY ........................................................... 104
FIGURE ‎5.6: FREQUENCY SPECTRUM PLOT OF TERMITE ACTIVITY ............................................................ 104
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FIGURE ‎5.7: IVANHOE EXPERIMENT SETUP ......................................................................................... 106
FIGURE ‎5.8: POWER POLE SOUND TEST SAMPLES ............................................................................... 111
FIGURE ‎5.9: SOIL FULL OF TERMITES (HORSHAM) ................................................................................ 113
FIGURE ‎5.10: HORSHAM EXPERIMENT SETUP ..................................................................................... 114
FIGURE ‎5.11: STAWELL EXPERIMENT ................................................................................................ 115
FIGURE ‎6.1: CONCEPTUALISATION OF AE TERMITE DETECTION SYSTEM.................................................. 122
FIGURE ‎8.1: LEGEND USED IN PRELIMINARY EXPERIMENT RESULTS ......................................................... 148
FIGURE ‎8.2: PRELIMINARY EXPERIMENT SOFTWOOD - ACROSS THE GRAIN RESULTS .................................. 152
FIGURE ‎8.3: PRELIMINARY EXPERIMENT HARDWOOD - ACROSS THE GRAIN RESULTS ................................. 154
FIGURE ‎8.4: PRELIMINARY EXPERIMENT SOFTWOOD - ALONG THE GRAIN RESULTS ................................... 155
FIGURE ‎8.5: PRELIMINARY EXPERIMENT HARDWOOD - ALONG THE GRAIN RESULTS .................................. 157
FIGURE ‎8.6: SECONDARY EXPERIMENT STAGE-1 TEST RESULTS ............................................................... 164
FIGURE ‎8.7: ANOVA RESULTS FOR 1KHZ INPUT FREQUENCY IN MATLAB® .............................................. 165
FIGURE ‎8.8: ANOVA RESULTS FOR 5KHZ INPUT FREQUENCY IN MATLAB® .............................................. 167
FIGURE ‎8.9: SECONDARY EXPERIMENT STAGE-2 TEST RESULTS ............................................................... 190
FIGURE ‎8.10: ANOVA RESULTS FOR 0.5KHZ INPUT FREQUENCY IN MATLAB® ......................................... 192
FIGURE ‎8.11: ANOVA RESULTS FOR 1KHZ INPUT FREQUENCY IN MATLAB® ............................................ 193
FIGURE ‎8.12: ANOVA RESULTS FOR 2KHZ INPUT FREQUENCY IN MATLAB® ............................................ 195
FIGURE ‎8.13: SOUND WAVE TRACES ................................................................................................. 196
FIGURE ‎8.14: FREQUENCY SPECTRA .................................................................................................. 197
FIGURE ‎8.15: FREQUENCY RESPONSE OF THE BAND PASS FILTER ........................................................... 198
FIGURE ‎8.16: SOUND WAVE TRACES FOR THE FILTERED RECORDINGS ...................................................... 198
FIGURE ‎8.17: MATLAB® CODE FOR BPF ............................................................................................ 198
FIGURE ‎8.18: FILTERED SOUND RECORDINGS WITH THE BACKGROUND THRESHOLD REMOVED .................... 199
FIGURE ‎8.19: MODIFIED MATLAB® CODE FOR BPF ............................................................................. 199
FIGURE ‎8.20: KRUSKAL-WALLIS ANOVA .......................................................................................... 200
FIGURE ‎8.21: THE AVERAGE NUMBERS OF DETECTABLE AE EVENTS IN TERMITE AND CONTROL SAMPLES ...... 200
FIGURE ‎8.22: TERMITE DETECTION IN WOOD STAKES EXPERIMENT RESULTS (TWENTY FOUR TESTS CONDUCTED)
.......................................................................................................................................... 215
FIGURE ‎8.23: TERMITES-IN-STAKES EXPERIMENT RESULTS (WOOD-TYPE BASED) IN MATLAB® ................... 217
FIGURE ‎8.24: STAKES-IN-BOX EXPERIMENT RESULTS IN MATLAB® ......................................................... 232
FIGURE ‎8.25: ELTHAM NORTH EXPERIMENT RESULTS IN MATLAB® ........................................................ 238
FIGURE ‎8.26: IVANHOE EXPERIMENT RESULTS .................................................................................... 261
FIGURE ‎8.27: BPF OF 3 TO 4.5KHZ PASS BAND DESIGNED BY AUDACITY ................................................. 261
FIGURE ‎8.28: THE FILTERED SIGNALS SPECTRUM AFTER APPLYING BPF ................................................... 262
FIGURE ‎8.29: IVANHOE EXPERIMENT RESULTS IN MATLAB® ................................................................. 263
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