Appropriate test conditions proposed for Industry Standards of measuring transformer noise

The subject of deciding on the most appropriate method and conditions for accurately measuring the noise level of a transformer has been discussed through the transformer industry for decades. It is the objective of this Paper to contribute to this effort by identifying more appropriate conditions for both the Sound Pressure Method and the Sound Intensity Method. The Paper presents results of comprehensive indoor measurements made of the frequency spectrum and total noise of a large number of power transformers using the two measuring methods. First, the paper presents data used to develop appropriate conditions for more accurate measurement of transformer noise using the Sound Intensity Method. The paper then presents data used to develop a more accurate and reliable Sound Wall - Reflection Correction to be used with the Sound Pressure Method. Lastly, the Paper presents appropriate method of measuring Load noise of power transformers. Sound measuring conditions developed and presented in this paper are being proposed to replace existing conditions in the IEC and IEEE Industry Standards of transformer noise testing.