1. When a single-phase grounding or resonance overvoltage occurs in the power grid, the sound of the transformer is sharper than usual;

2. When a large capacity power equipment is started, the load changes significantly, causing the sound of the transformer to increase. When a transformer is equipped with loads such as electric arc furnaces and controllable silicon rectifiers, due to the presence of harmonic components, there will be an instantaneous "wow wow" or "giggle" intermittent sound inside the transformer;

3. Overloading causes the transformer to produce a high and heavy buzzing sound;

4. Individual parts are loose, such as loose screws on the iron core or missing parts on the iron core, causing strong and uneven "noise" or "hammering" and "blowing" sounds from the transformer;

5. Poor internal contact of the transformer or insulation breakdown, causing the transformer to make a "cracking" or "squeaking" sound, which varies with the distance from the fault point;

6. When the system is short circuited or grounded, a large short-circuit current will cause the transformer to make a "crackling" noise, and in severe cases, there will be a loud roar;

7. When ferromagnetic resonance occurs in the system, the transformer produces uneven noise in thickness.