Jump to the thesis to download/read.
(Note: This is for bubbles in liquids, gas in liquid - not soap bubbles, gas inside liquid film inside gas. For a science introduction to soap bubbles, I recommend the classic 'Soap Bubbles: Their Colors and Forces Which Mold Them' by C. V. Boys. First published in 1911 & still in print because it is so informative & enjoyable.)
The acoustics of bubbles was my PhD subject. A mixture of experimental physics, theoretical physics and electronic engineering at the Cavendish Labs in Cambridge University 1991–1994 under supervisor Alan Walton. In total contrast to my work before or after, those 3 years involved no computer programming.
Alan was formerly an Open University lecturer on TV, the writer of a best selling undergraduate physics textbook (The Three Phases of Matter) and the writer of a humorous, but informative, book on lecturing. Hence he was keen for me to write in an easy to read flowing manner and, where possible, not require the reader to have specialist knowledge. I learnt from him & so my resulting thesis is an uncommonly easy read (&, controversially, has artwork & humour in places).
The aim was to measure bubbles by sound. Originally the intention was to use subharmonic modulation, as advocated by a supervisor (who left the day I started). I found that was very unreliable. Indeed his claimed mechanism for the effect was wrong & I found the real cause of the subharmonics was something more prosaic. However I & Alan discovered two new simple & reliable ways of measuring bubbles by sound. One of which overturned decades of many researchers starting papers with the equivalent of "obviously not worth trying that simple method as it won't work, so here is our attempt at a complex new method". And the reliability was so high that I got referees asking why my graphs did not have error bars - they were smaller than the data points could be printed!
However it was in the days before papers were fully written digitally. The text & equations I wrote on a computer (they are on floppy disks) but the figures were separate, many hand-drawn, & combined in by the publishers. So I'd need to scan in the figures from the paper papers, retrieve the original text and combine them; plus make ALT-text for web accessibility. As my academic subject changed totally after the PhD (albeit using the skills I learnt there of making unusual devices ad hoc from anything), it was low priority. The papers (& thesis) were in libraries. However nowadays, papers that are not online are not read. So I need to get round to digitising them.
Fortunately I did start on digitisation in 2002 with scanning in all the figures for my PhD thesis, converting the text to a newer file format & combining the two. The thesis covers all the useful content of the papers plus more. However in 2002 it was too big for the web with figures in as MS Word or PDF and, as I was working then on blind accessibility, I thought it hypocritical not to include ALT-text for all the equations & illustrations and got bogged down on that. Also there was still one paper to publish from it & academic convention is that papers should be published the thesis is made fully public but, no longer working in the subject, I did not have the time at work to deal with the cumbersome rituals of referees & journals. Jumping forwards to 2024, I discovered in a self-promotional Wikipedia page that one of my discoveries had been republished without credit by a rival as their own major discovery - indeed by the very person whose hypothesis it disproved! It reminded how back-stabbing academia was, that journal publication was mainly grant getting & politics I no longer needed and that I should put the material on the web to set the record straight.
So, starting with the thesis:
My recommendation for reading on my contribution to the subject. It is also good for the for the subject background without being too long-winded. Unlike the papers which were on one study each & constrained by academic publishing format, I wrote this more like a book; and made colourful illustrations. It does not require more than A Level physics and maths for full understanding and most of it does not even require more than O Level. Indeed other than the maths bits (all of which are explained in mechanistic terms, not abstract magic), it is mostly readable without even that.
Formats available: