Field Study of Sound Radiation by Power Transformers

Information needed for the acoustic design of power transformer installations required to meet specific property line noise criteria was obtained through a study, in the field, of 40 in-service power transformers. This paper reports on the unique method of data acquisition and of data reduction; summarizes the information gained by the analyses of the nearfield and farfield noise measurements regarding (1) the tonal composition of the core noise, (2) the circumferential statistics of the sound radiation pattern, (3) the variation of the noise level with distance, and (4) the relation between noise levels measured at NEMA positions and in the far field; and recommends improvements in the standard transformer noise measurement method that would yield information about the tonal characteristics of the transformer noise.