A high-frequency, shallow-water acoustic measurement system

The US Naval Ocean Research and Development Activity has developed a high-frequency acoustic measurement system for use in shallow water. The heart of this system is a pair of submersible towers supporting acoustic transmitting and receiving instrumentation. These towers are transported to an experimental staging area, assembled, and acoustic instrumentation installed. They are towed to a preselected measurement site, then the chambers on each tower are flooded, thereby settling slowly to the ocean bottom. Stability and dynamic response analyses were used to determine the towing and deployment stability envelopes for the towers. The acoustic transmitting system uses a pair of narrow-beam parametric acoustic sources operating at secondary frequencies ranging from 20 to 180 kHz. The acoustic receiving systems consist of a pair of 16-hydrophone, two-dimensional arrays with broadband capabilities up to 250 kHz. These systems have been used to make high-resolution bottom scattering measurements in shallow water off the coast, south of Panama City, Florida