Underwater Acoustical Measuring Facilities at the U. S. Navy Underwater Sound Laboratory

During the war the Underwater Sound Laboratory at New London carried on much of its acoustical test work on a sound barge located at the laboratory pier in the Thames River. Relatively shallow water and the high noise level resulting from rough water, passing ships, and manufacturing establishments located on the water front reduced the usefulness of this barge. A second sound barge was therefore installed on a small inland pond not far from the laboratory. It is intended to use this barge to satisfy the exacting demands of long-term tests of scanning sonar transducers and systems and to serve as a center for developmental research in measuring techniques. The barge is located at the end of a 300-foot pontoon pier in 48 feet of pure and practically noise-free water. It has a four-foot by twenty-foot well with one movable hoist column and one training hoist column. The electronic gear on the new barge is capable of measurements over a frequency range from two to 150 kc. Among the types of measurements made are: (1) frequency responses, receiving, and projecting; (2) directional patterns (polar or rectangular); (3) reciprocity calibrations; (4) admittance measurements; and (5) phase measurements. For frequency responses, a Leeds and Northrup “Speedomax” recorder is used. For directional patterns, the recorder is linked to a polar turntable by a mechanical linkage.