DOEI Postdoctoral Scholar
August 2012 - May 2014
David joined DOEI in December 2012 after obtaining a PhD from Scripps Institution of Oceanography and working as a postdoc at Memorial University of Newfoundland. His research is focused on using naturally generated ambient noise to study the processes that cause sound generation in the ocean and the properties of various oceanographic environments through which sound propagates. A large part of this work involves the engineering and design of acoustic recording systems that are sensitive enough to measure background noise levels, yet robust enough to withstand the ocean’s harsh environment. As a graduate student, he built the instrument ‘Deep Sound’, which has made depth-profile ambient noise recordings in the Tonga Trench and the Mariana Trench at depths of 9 km, a new measurement in the ocean acoustic field. One of his main research goals at WHOI is to model the spatial distribution of ambient noise in the deep ocean and relate noise measurements to key elements of the propagation environment such as topography (trenches, canyons, sea mounts), seabed properties, oceanography (internal waves, sound speed profile variability) surface processes (wind, rain, sea ice).
This work is being done in collaboration with Ying-Tsong Lin, a scientist in the Applied Ocean and Engineering department and an expert in three-dimensional parabolic equation propagation modeling. By exploiting the wave equation’s reciprocity, noise fields due to non-uniformly distributed surface processes in complex 3-D environments can be efficiently calculated from a single propagation simulation. The feasibility and computational limits of this technique have been tested against data collected by Deep Sound and existing analytical models for simple ocean environments. With knowledge of these limits, the technique is now being pushed to calculate spatial properties of the ambient noise field in an arbitrarily complex environment.
David has also proposed to use the deep ocean noise measurement capability to study uncharacterized sound mechanisms in the ocean, such has hydrothermal vents and cold seeps. Using array processing techniques and knowledge of the sea surface and meteorological conditions, noise from a hydrothermal vent could be distinguished from the ocean’s ambient noise and used to infer physical properties of the vent’s structure and outflow. Preliminary work is now being done on this problem, to be followed by field measurements in the near future.