Transformer Noise

[EEuno]

I have a noisy dry type, 75KVA step down transformer. Does anyone know at what distance from the transformer a proper sound measurement is to be made to insure compliance with ST20 specifications?

 

[MAGTiger]

There's kind of a lot to it. But in summary, for your 75kva, you need to make measurements at 3 foot intervals around the unit at elevation of half it's height. The instrument should be one foot from the "sound producing surface" but there can be no less than 4 readings located in the 3 foot increments. There's also a table to correct for ambient noise.



Neil