A sound Laboratory on wheels

To help University of Rhode Island marine scientists listen in on the sounds made by the animals of the sea, the Graduate, School of Oceanography has acquired with Navy funds a unique sound laboratory built into an automobile.

The research project in which this equipment is used is directed by Mrs. Marie P. Fish, research oceanographer, and is supported by the Office of Naval Research. lts purpose is to increase understanding of the sounds in the sea that are of biological origin and, by means of tape recordings of the "voices'' undersea, attempt to determine which animals make sounds; what, where, how, and when they may be encountered.

The mobile laboratory in a grey Chevrolet sports wagon labeled U.S. Navy 93-0846 may be driven on a moment's notice to any point where recordings are to be made. Inside is highly refined electronic recording and sound-measuring equipment as well as a self-contained generator to provide necessary power. Interior structure and arrangement of equipment was planned at URI, and at present this is the only such laboratory in existence.

Reels of cable 100, 200 and 400 feet in length make it possible to take the 18-inch underwater microphone considerable distances from the recording instruments. A two-way radio system and several "walkie talkies'' provide speedy communication.

Atop the car is a 12-foot aluminum boat from which lightweight, portable battery and transistorized recorders are used. In fact, it is an elusive underwater sound that escapes this adaptable equipment.

Whenever it is practicable, the fish to be auditioned is placed in a special monitoring aquarium. The mobile laboratory has a wooden platform with series of rubber pads underneath to deaden ground-carried sound, and on this a collapsible canvas tank is installed in which the specimen is placed. All this fits neatly into the car when not in use.

The mobile laboratory had its first test run in December when Mrs. Fish, Paul J. Perkins, oceanographic specialist, and William H. Mowbray, research assistant electrical engineer, drove the car northward along the coast as far as Boothbay Harbor, Maine, to make recordings of the winter "underwater chorus," and study the soundmaking of various marine animals collected for them by the U. S. Fish and Wildlife Service and the Maine Sea and Shore Fisheries stations.

Mrs. Fish explains that with this mobile laboratory, the scientific team on underwater sound will not only be able to get quickly to spots where there is something to record, but they will be able to put the entire mobile laboratory aboard ship or transport plane to use at distant spots. Greenland is one place where she has been invited to make sound studies.

The underwater sound research project at the University of Rhode Island has been in existence since 1946 - longer than any other Office of Naval Research biological program. Funds supporting it at URI in the year just ended total $89,000; this includes funds for open ocean study of zooplankton by Mrs. Fish's husband, Dr. Charles J. Fish. Equipment for continuous sound recording has been in operation in Narragansett Bay near the Graduate School of Oceanograpy for the past three years and results are under constant study. The mobile laboratory supplements this and makes the program more flexible.

The sound research project is special interest to the Navy in relation to the sounds submarines and surface vessels using sonar pick up and must identify. The strength of sound produced marine animals is considerable and is produced by such van mechanical methods as vibrating air bladders, rubbing together modified teeth, or snapping body parts. During World War II the sound made by a toadfish, native here, was found to be capable of exploding the type of mine then in use, which led to redesign of some defense equipment.

When the undersea sounds have been fed through a Navy noisemeasuring set and recorded on tape, unwanted noises are filtered out and the remaining sounds are thoroughly analyzed. The pattern and frequency components of each sound are recorded as graphs on a revolving disc. Each underwater source of sound has its own characteristic ''signature." A toadfish and a shrimp not only sound different, but the pictures of their voices" look different. Two principal types of graphic representation of sound which are prepared from tapes are oscillographs and sonagrams.

During their studies of underwater ambient sound in this area, the team kept hearing a persistent background crackle similar to that made by snapping shrimp in the tropics. They eventually identified it as the sound made by the black or edible mussels when the elastic byssal threads that attach them to each other and to rocks or pilings are broken as they move.

"Educated ears'' are a great advantage in this work, Mrs. Fish explains. Perhaps at some time a method may be developed for mechanically evaluating sounds as they are recorded, but at present much of this must be done by. human beings. Paul J. Perkins, who joined the staff in July 1962, is said to have the ''best pair of ears in the Navy.'' He set up the first Sonar Information Center in Hawaii. Mr. Mowbray who is responsible for the technical electronic side of the work, has been associated with Mrs. Fish in bioacoustic research since 1950 when he graduated from URI as an electrical engineer. He is now a Ph.D. candidate in the Graduate School of Oceanography.

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