A Calculated Defense Effort
Mathematics research can provide solutions to many real-world problems in such areas as medicine, pharmaceuticals, manufacturing and business. But the work of Professor Eliza Michalopoulou in ocean acoustics has an even more compelling and timely bottom line – national defense.
With expertise in both mathematical analysis and signal processing, she studies how sounds move in the ocean and how they are affected by factors like temperature, ocean depth, seafloor composition and currents. The main goal is to help the U.S. Navy, which supports her research through the Office of Naval Research, to identify better techniques for detecting submarines, particularly along the nation’s seacoasts.
Using analytic and numerical techniques such as such as matched field processing and inversion analysis, she studies oceanic sound propagation and localization, including the influence of geological features beneath the ocean floor that must be acoustically imaged. The end products of her work are algorithms that can be used in developing next-generation security and environmental monitoring systems. With colleagues from the Scripps Institution of Oceanography, she has been recently developing new methods for localization of sound sources and estimation of properties of the ocean seabed. These techniques, detailed in a 2011 paper in IEEE Journal of Oceanic Engineering, exploit dynamic relations between sound data and their relationship to the location of the sources as well as the properties of the ocean.
As she explains, many factors influence the propagation of sound in such environments. Among them are water temperature, the number of times sound waves bounce between the surface of the ocean and the earth below, the slope of the ocean floor and its subsurface geologic profile. It’s also necessary to factor in the identifying characteristics of a sound source — sea life or submarine — and the noises of civilization emanating from shore and nearby surface vessels.
The raw material of Michalopoulou’s oceanic insights is a growing body of data obtained from various sources, most notably ONR colleagues, to which she applies mathematical techniques to help to address the problems of oceanic sound propagation and localization, including the influence of geologic features beneath the ocean’s floor that must be acoustically imaged. The end products of her research are special algorithms, or precise mathematical tools, that may eventually be applied in next-generation systems for protecting the shores of the U.S. against unauthorized underwater incursions.
In addition to her work in ocean acoustics, Michalopoulou has also explored how her algorithms can be applied to problems involving light reflections from bodies of water. In a paper published last year in IEEE Transactions of Geoscience and Remote Sensing with Professors Sima Bagheri and Lisa Axe from the Department of Civil and Environmental Engineering, she demonstrated how such algorithms can be successfully applied to models and data relating chlorophyll concentration in estuaries and light sensed by satellites with the aim of detection pollution.