Reduction of Noise Produced by Small and Medium 2-Pole Turbine Generators [includes discussion]

In 1945, a systematic program aimed at reducing the noise level of their small and medium size 2-pole turbine generators was undertaken by the company with which the authors are associated. Factory tests on over 110 air-cooled generators ranging from 1,000-kw to 12,500-kw rating indicate that the average noise level of this line of machines has been reduced over 6 decibels. This noise level reduction has been brought about primarily by reducing sound energy transmission. One of the most important methods of reducing sound transmission is to keep the natural mechanical frequency of any part well away from any of the forcing frequencies. A discussion is given of the analytical work, the design program, the test equipment, and the development of a test procedure for obtaining consistent test results. The methods used in this program are general, and are applicable to the reduction of noise generated by other electrical apparatus.