Expendable Acoustic Source for AUV Based Geoacoustic and Geotechnical Survey Operations Navy STTR FY2012.A Sol No.: Navy STTR FY2012.A Topic No.: N12A-T017 Topic Title: Expendable Acoustic Source for AUV Based Geoacoustic and Geotechnical Survey Operations Proposal No.: N12A-017-0048 Firm: Analysis, Design & Diagnostics, Inc. 317 West Forsyth St. Jacksonville, Florida 32202 Contact: Gary Donoher Phone: (904) 475-0094 Web Site: http://www.adndinc.com Abstract: Our team proposes a unique expendable acoustic source comprised of flexural disc technology in a close packed arrangement that allows for a reduction in resonant frequency and an increase in useful bandwidth. This array will be designed to couple as much energy as possible into the bottom sediments, while coupling as little energy as possible directly into the surrounding water column. This is a difficult task for an unspecified and potentially unknown bottom type, but an array of flexural discs designed to sit on the sea floor will make it possible to achieve this goal in many cases. Our source will generate continuous M-sequence waveforms which are excellent for geoacoustic inversion. M-sequence waveforms will be used to provide significant information on the structure of bottom sediments by simultaneously providing very high resolution in both time delay of arrival and Doppler space, limited only by the coherence of the medium. M-sequence waveforms exhibit a white spectrum and, after the specified detection processing, will provide the desired thumbtack ambiguity function, i.e., high resolution in both time of arrival and Doppler space. Benefits: The Naval Oceanographic Office is responsible for the generation of N-layer low-frequency bottom-loss (LFBL) and the HFBL databases. LFBL and HFBL are based on acoustic and seismic measurements performed at-sea by NAVOCEANO survey teams. These surveys are expensive to perform, are restricted by environmental regulations (Marine Mammal Protection Act) and are difficult to perform in littoral waters of interest because of geopolitics. Our solution is a low-cost, bottom mounted, calibrated, Expendable Acoustic Source (EAS), which is environmentally friendly and easy to deploy. This EAS could be deployed in littoral areas of interest by almost any platform and the data could be readily integrated in the LFBL/HFBL databases. Not only would this source be useful in populating the LFBL/HFBL databases, the calibrated source could provide significant additional information about shallow water propagation while also providing information on the characteristics of the bottom sediments which might be useful in identifying buried mines or in seeking favorable geologic structures for undersea oil and gas exploration. Return