Study and Test Report for Low Levels of Structureborne and Airborne Noise of Motor-Generators for Shipboard Service

摘要

The study was undertaken to analyze those factors (Mechanical and Electrical) which produce structureborne and airborne noise in motor-generators, excluding their electrical control, and to determine how the noise producing factors can either be eliminated or reduced to a minimum. Motor-generators of the type built are used on shipboard as electrical conversion equipment in changing from direct current input to 400 cycle alternating current output. Such units are inherently noisier and produce more structureborne and airborne noise than either a DC machine or an AC machine of the same rating. The two machines with one common shaft and two bearings can interact with each other in exciting resonant vibrations, thus building up the magnitudes of the vibrations and the intensities of the noise levels. Three major considerations are necessary in designing and building motorgenerators with low magnitudes of structureborne and airborne noises for quiet operation in shipboard service. Optimum design for low noise level with shipboard service limitations on size, weight, performance, and ability to withstand shock. Quality materials, excellent manufacture, and complete and accurate tests. An adequate mounting or supporting system to minimize transmission to the ship's hull of those structureborne noises that cannot be further reduced in the machine itself. (Author)