Woon Siong Gan  obtained  PhD at the age of 24.  He obtained BSc in physics in 1965, DIC in acoustics & vibration science in May 1967 and PhD in acoustics in Feb 1969, all from the Imperial College London.  His PhD thesis pioneered the statistical mechanics approach to ultrasound propagation in semiconductors.  The usual approach is electron-phonon interaction of many body theory.  It is also the first to introduce the concept of topological phase transition.  The thesis title Transport Theory in Magnetoacoustics pioneered the introduction  of transport theory to condensed matter physics.  Transport theory is today the key foundation of theoretical design of materials.  Hence his thesis also played a role in the founding of the field of condensed matter physics.  He also recently discovered the singularity behaviour of transport properties and resonance is singularity.  In 2007 he pioneered the introduction of gauge invariance to acoustic field  equations.  Acoustic metamaterial is an outcome of gauge transformations.  He is currently working on the application of gauge invariance to nonlinear acoustics such as multiple scattering, inverse scattering, and interactions.  He has published the book Acoustical Imaging:Techniques & Applications by John Wiley & Sons in 2012, the book New Acoustics, based on Metamaterials by Springer in 2018 and several papers on acoustical imaging and gauge invariance in acoustics. He is a Fellow of the Institute of Acoustics, UK, a Fellow of the Engineering & Technology Institute,UK, a Fellow of  the Institution of Engineers,Singapore, a Fellow of the Southern African Acoustics Institute, a Senior Member of IEEE, a Senior Member of the American Institute of Ultrasound in Medicine, and a Member of the Acoustical Society of America.