Keynote: A. B. Wood Medal Lecture: The underrated phase

Underwater acoustics overlap a multitude of scientific fields, from mathematics and physics to mechanics and electronics, to gives some examples. Over several decades, underwater acoustics brought together researchers from various different backgrounds. and it is this plurality of expertise and contributions that makes underwater acoustics such a vibrant domain to work in. Despite the relatively small community, great challenges have been overcome over the years such as the sound propagation problem or more recently the micro-navigation problem for synthetic aperture systems. My background in signal processing always pushes me to extract as much information as possible from any sort of data set given certain priors. The priors in question here are given by the physics of acoustics and in particular the interaction between sound and matter on which I specialised over the years. One overlooked information lies in the phase of the acoustic signal. Traditional sonar systems have evolved in recent decades into sophisticated imaging systems. The underlying reason behind this choice is that as human observers, we are more comfortable with images than we are with one-dimensional signals, in this case the sounds themselves. Imaging sonars have come a long way and have improved dramatically in terms of noise and resolution. However, the image formation process, and most notably the envelop detection processing, suppresses all of the information contained in the phase of the signal. During this presentation, I will talk about this specific issue of phase information which guided my research on wideband sonar, but also how to exploit the phase by designing coherent multistatic systems such as MIMO (Multiple Input Multiple Output) systems.