Power transformers located in outdoor substations can be a significant source of environmental noise disturbance, especially during nighttime hours. The dominant characteristic of transformer noise is the low frequency “hum” generated within the magnetic core as a result of the magnetostrictive properties of the core steel. The core-generated noise consists of the harmonics of the fundamental frequency, 120 Hz (twice line frequency). The noise of a transformer is virtually independent of the load carried. The paper reports observations and findings of an extensive survey carried out by BBN and additional data provided by BPA and ESEERCO.
Ungar, E. E., and Gordon, C. G., “Vibration Challenges in Microelectronics Manufacturing,” Shock and Vibration Bulletin, 53(I):51-58 (May 1983). [Elias Klein Memorial Lecture] Colin G. Gordon and Lennart A. Swenson, “Power Transformer Noise—Prediction and Control”, Proceedings of Inter-Noise 78, pp. 323-328.65ed834e9c80e78034a899e748f7f633