Acoustic Sensor Technology Saves Manatees

Manatees are large marine mammals, streamlined in shape, with adults averaging 1,000 to as much as 1,500 pounds in weight. Adults reach a length of about 12 feet. They are an endangered species that, due to their slow maneuverability and penchant for warm water off the coast of Florida, often get killed in collisions with boats or by entrapment in man-made structures and nets. The new protection system at Port Canaveral, operated by acoustic sensors, is designed to prevent the lock gates from closing if a manatee is detected. This system will reduce risk, injury and mortality of manatees and enhance the Port's manatee protection efforts.

The Manatee Protection System contains a total of 320 individual sensors installed in sensor "packages" of 10 sensors each, with eight such packages on each gate. The engineers who designed the system wanted ultimate safety and redundancy; any one sensor can go off-line without disabling the entire system. The system operates similar to a garage door opener that immediately stops if it senses someone or something beneath the door. At Port Canaveral, a break in the acoustic signal alerts the gates to stop closing, giving any manatees time to get clear of the gates.

The ONR Materials Division initiated development of the piezoelectric material used in the acoustic-based sensor system that can react to the passage of a manatee in a tenth of a second. Funding for the project was awarded through ONR's Small Business Innovation Research Program. Additional funding was provided by the Defense Advanced Research Projects Agency.

A piezoelectric material tranforms electrical energy into mechanical energy and vice versa. Installing the new Manatee Protection System at Port Canaveral consisted of retrofitting both gates of the Canaveral lock structure with an acoustic system composed of emitter and receiver units. The units are made from state-of-the-art piezoelectric composite transducer elements. Some other applications of the system's composite transducers are submarine sonar, surface ship mine hunting, nondestructive testing, medical ultrasound, and seismic exploration.

--USN--

The Office of Naval Research pursues an integrated science and technology program from basic research through manufacturing technologies. Research areas include oceanography; advanced materials; sensors; electronics; surveillance; mine countermeasures; weapons; and surface ship, submarine and aircraft technologies. For more information about ONR programs, refer to the ONR home page at http://www.onr.navy.mil on the World Wide Web.