DRDC Atlantic to participate in major US Office of Naval Research field experiment

The US Office of Naval Research (ONR) is providing $400,000 US to DRDC Atlantic to support their participation in a major field experiment, Sediment Acoustics eXperiment 2004 (SAX04). Researchers participating in SAX04, led by the Applied Physics Laboratory at the University of Washington (APL/UW), will conduct experiments to investigate the interaction of sound with the seabed for naval applications. DRDC Atlantic is working closely with the Applied Research Laboratory at Pennsylvania State University on this project.

Data collected during a previous ONR experiment in 1999 suggested that the speed of sound travelling through seabed sediments might depend on the sound frequency, especially when the seabed is principally composed of sand. This behaviour contradicts a long-standing assumption in underwater acoustics that the speed of sound is independent of frequency.

This discovery will have implications for systems used to predict the performance of naval mine hunting and submarine sonar in a variety of environments. It will also impact geological sampling techniques that have been used extensively to provide “ground truth” measurements of sediment sound speed. These measurements are done at much higher frequencies than those of naval operations. For scientists, these observations will provide a method for evaluating competing theories, some new and some revived, that seek to explain the physics of how sound propagates in marine sediments.

Since June 2003, DRDC Atlantic scientist, Dr. John Osler, has been leading a team of scientists, engineers, technologists and students at DRDC Atlantic as they convert the experimental concepts into research equipment that can be deployed on and into the seabed.

Prior to that, in the fall of 2002, ONR had asked Dr. Osler and Dr. Paul Hines, DRDC Atlantic, to review the results from the 1999 experiment and develop novel experimental concepts that could be used to make a new and more robust set of measurements for this data. ONR accepted that proposal which led to the awarding of the current three-year grant. The funding consists of a three-year $200,000 research grant and an equipment budget of $200,000.