A study of sound levels of transformers

Much has been accomplished in the past few years in understanding the problem of transformer noise. It has been definitely established that magnetostriction discovered by Joule in 1842 is the principal source of transformer noise. The various harmonic vibrations generated in the core by magnetostriction have been analyzed. Methods of calculating sound levels in terms of the standards prepared by the American Standards Association have been developed. A large number of modes in which different core structures may vibrate have been determined experimentally and analytically. As a result, methods for determining the correct design proportions of the core have been developed so that the natural modes of vibration may not coincide with the harmonic vibrations generated by magnetostriction. These methods have been successfully applied to actual designs of transformers including the largest ratings.