An Acoustic Screen for Making Underwater Noise Reduction Tests in Pearl Harbor

Abstract

When the German submarine menace had been largely overcome during World War II, the attention of our Navy and scientists turned toward reducing the noise of our submarines in order to make them less readily detectable. To accomplish this required improvements in the submarine noise-measuring techniques. In Pearl Harbor, where there often were eight hundred ships of all kinds, the underwater noise level was high. There was no place found where noise measurements could be made satisfactorily, and therefore special methods had to be developed. After extensive study it was decided that the best arrangement would be to insulate Auxiliary Repair Docks, and measure the noise of submarines while they were in the docks. This was done by the development of a suitable air-bubble screen across the open end of the dock. Such an acoustic barrier was comparatively easy to install, did not interfere with submarines entering and leaving, kept ocean surface oil out of the dock, insulated against low as well as high frequency noises as was required, and, after extensive experimentation, the noise of the screen was reduced to a level that did not interfere with the noise measurements. The insulation of the screen upon the noise of a nearby submarine-charging batteries is illustrated by a phonograph recording.