xvi ◾ Preface to First Edition
e application chapters are essentially a whistle-stop tour of work by a large num-
ber of researchers around the globe. Some examples of this work are discussed in more
detail than others and, in addition, a large number of illustrations have been used which
have been taken (with permission) from a variety of published material. e examples and
illustrations used have been chosen to provide an appropriate range to best illustrate the
wavelet-based work being carried out in each subject area. It is not intended to delve deeply
into each subject but rather to provide a brief overview. It is then le to the reader to fol-
low up the relevant references cited in the text for himself or herself in order to delve more
deeply into each particular topic as he or she requires.
I refer to over 700 scientic papers in this book which I have collected and read over the
past three or so years. I have made every eort to describe the work of others as concisely
and accurately as possible. However, if I have misquoted, misrepresented, misinterpreted
or simply missed out something I apologize in advance. Of course, all comments are wel-
come – my e-mail address can be found below.
e book stems from my own interest in wavelet transform analysis over the past few
years. is interest has led to a number of research projects concerning the wavelet-based
analysis of both engineering and medical signals; including non-destructive testing sig-
nals, vortex-shedding signals in turbulent uid ows, digitized spatial proles of structural
cracks, river bed sediment surface data sets, phonocardiographic signals, pulse oximetry
traces (photoplethysmograms) and the electrocardiogram (ECG), the latter leading to pat-
ent applications and a university spin-o company, Cardiodigital Ltd.
Quite a mixed bag, at rst appearance, but with a common thread of wavelet analy-
sis running throughout. I have featured some of this work in the appropriate chapters.
However, I have tried not to swamp the application chapters with my own work – although
the temptation was high for a number of reasons, including knowledge of the work, ease of
reproduction, etc. I hope that I have struck the correct balance.
All books reect, to some extent, the interests and opinions of the author and, although
I have tried to cover as broad a range of examples as possible, this one is no exception.
Coverage weighs more heavily towards those areas in which I have more interest: uids,
engineering, medicine and fractal geometry. Geophysics and nance are given less space
and other areas (e.g. astronomy, chemistry, physics, non-medical biology, power systems
analysis) are detailed briey in the nal chapter.
ere are some idiosyncrasies in the text which are worth pointing out. I am an f person
not an ɷ person: I prefer hertz to radians per second. I can tap my ngers at approximately
5 Hz, or 1 Hz, I know what 50 Hz means (mains hum in the UK) and so on; however, ɷ
I have to convert. Hence the frequencies in the text are in the form of 1/time either in
hertz or non-dimensionalized. e small downside is that the mathematics, in general,
contains a few more terms – mostly 2s and πs. I have devoted a whole chapter to the con-
tinuous wavelet transform. It is noticeable that many current wavelet texts on the market
deal only with the discrete wavelet transform, or give the continuous wavelet transform
a brief mention en route to the theory of the discrete wavelet transform. I believe that
the continuous wavelet transform has a wide variety of data analysis tasks to oer, and
I attempt, through this text, to redress the balance somewhat. (Actually, the proportion