Transformer noise is the sum of mechanical noise and air noise caused by irregular, intermittent, continuous, or random noise generated by the transformer body and cooling system during the design, selection and layout, installation, and use of the body. The noise generated by transformers widely affects residential quarters, commercial centers, light stations, airports, factories and mines, enterprises, hospitals, schools, and other places.

Specifically, there are three sound sources of transformer noise, one is the iron core, the other is the winding, and the third is the cooler, that is, the sum of the noise caused by the no-load, load, and cooling system. The reason for the noise of the iron core is that under the action of the alternating magnetic field of the silicon steel sheet that constitutes the iron core, there will be small changes, namely magnetostriction. Magnetostriction causes the iron core to vibrate periodically with the change of the excitation frequency. caused by internal electromagnetic forces.

The reason for the vibration of the winding is that the electromagnetic force is generated in the current winding, and the leakage magnetic field can also make the structural parts vibrate. The reason for electromagnetic noise is that the magnetic field induces the longitudinal vibration of the core laminations to generate noise. The vibration amplitude is related to the magnetic flux density in the core laminations and the magnetic properties of the core material but has little to do with the load current. The electromagnetic force (and vibration amplitude) is proportional to the square of the current, while the emitted sound power is proportional to the square of the vibration amplitude.

The noise of the transformer in operation usually refers to the noise synthesized by the noise of the transformer itself and the noise of the cooling device. Therefore, in order to reduce the noise of the transformer, effective technical measures should also be taken from these two aspects. At present, the domestic transformer noise testing institutions include the Building Physics Laboratory of Tsinghua University.

On the one hand, the main body noise of the transformer can be controlled by reducing the vibration of the iron core and reducing the divergence ability of the noise; the noise can also be attenuated in the propagation path by measures such as vibration reduction, sound insulation, and sound absorption.

On the other hand, controlling the noise of the cooling system so that the noise is close to or lower than the noise level of the main body can also effectively reduce the noise of the transformer.