Jake Defilippis
Title: Stairway to Triplication: The Importance of Oceanographic Fine-structure for Acoustic Signal Processing
Abstract: Advances in ocean sensing and ocean acoustic technology allow for the concurrent collection of spatially distributed observations of fine-scale (<10 m) ocean variability while monitoring sub-millisecond changes in the acoustic channel impulse response. The relevance of fine-scale ocean variability to mid-frequency acoustic propagation is explored with a pair of state-of-the-art at-sea campaigns, where short-range (1-6 km) acoustic transmission experiments were conducted within a densely sampled ocean environment. These experiments were designed to investigate a currently open question in ocean acoustics: how does variability in the acoustic channel impulse response on signal processing timescales, which are seconds to minutes, relate to internal-wave-driven changes in the ocean sound speed field on timescales of tens of minutes? We find that 5- to 10- meter scale changes in the ocean's vertical sound speed gradient allow for acoustic propagation pathways that interfere with each other. The interference between these acoustic pathways is sensitive to small vertical displacements of the sound speed profile. The internal wave variability combined with fine-scale sound speed structure de-correlates the carrier phase of mid-frequency acoustic pulses twice as fast as propagation without interference. This effect is important for many ocean sensing and communications applications, as well as cementing our fundamental understanding of multi-path propagation in the ocean.
Bio: Jake DeFilippis is a 4th-year Ph.D. candidate working with Bruce Cornuelle and Drew Lucas on oceanographic and ocean acoustic problems. He received his bachelor's degree in physics and computer science from the University of California Santa Cruz, and received his master's degree in electrical engineering from the University of California San Diego. Jake is interested in ocean acoustics specifically in its application to remote sensing of oceanographic processes. Contact: jdefilip@ucsd.edu