Where did you go on vacation last summer -Walt Disney World, the beach, or maybe on a cruise? Carl Frederickson, associate professor of physics and astronomy, went to the Naval Research Laboratory in Washington D.C.
Frederickson was part of a research team that is working with the Navy to find a technique for scanning shallow water for explosives such as mines and other potential threats that may be buried near the shore. “We want to build something that will allow Naval vessels to scan the shallow water for possible threats as it enters a port,” he explained.
Frederickson said this has not been possible before because the techniques used to search for objects are not able to scan a large area quickly. Current methods only look at a small area at any given time and can take a long time to complete a search of a large area.
The summer study used sonar waves to locate objects buried at shallow depths in the ocean. A research team of eight used a transducer (an underwater speaker) and hydrophone (an underwater microphone) to scan the ocean floor. Sounds were emitted underwater by the transducer and then absorbed by the hydrophone after they bounced off the ocean floor. The variation in the sound waves allowed the team to locate and identify buried objects.
During the research, which was conducted over the last five summers, different techniques were used to see which one gave the best sound penetration. The techniques used were evanescent waves, and rough surface scattering. Rough surface scattering allows sound to cross from the water into the bottom directly through the peaks and valleys in the surface. Evanescent waves are created when sound waves hit the bottom at a small angle. This technique does not penetrate very deep into the bottom. The evanescent waves were found to be the most efficient technique for locating buried objects in a laboratory experiments. The reflections from evanescent waves were easier to distinguish because the surface was smooth.
While at the Naval Research Laboratory, Frederickson’s job was to analyze the data that the researchers in the field found. This was not Frederickson’s first time to conduct research at the Naval Research Laboratory. In fact, it was his fifth time. Frederickson’s interest in this type of study dates back to the early 1990s when he was doing his post doctorate work. “I have always had an interest in science, but while I was doing my post doctorate work at Old Miss, I began to gain an interest in studying the acoustics of porous media like shallow sea bottoms,” he said.
Frederickson brought his non-classified research findings back to UCA this fall to share with his students. “I was able to show them how we found rocks and oil drums in shallow water,” he said. “I would love to be able to do this type of research here, but it is not easy.”
Frederickson said that since the university does not have the large tanks that would be necessary to conduct the same experiments he worked on at the Naval Research Laboratory, the only other alternative would be to build a scale model.
-Anna Lacy
