'Hum' Noise in Transformers – Causes and Ways to Reduce it

Noise in Transformers – Causes and Ways to Reduce it.

It is common to see an electrical transformer near your locality. While passing by your street near to the transformers, you might have heard a continuous vibration like noise near the transformers which seems like “hum.”. If you have not noticed then do it next time when you visit a transformer.

In this post I would like to describe why there is a noise in a transformer, though it seems, nothing is moving inside it unlike electric motors and generators. Actually, inside the transformer there is no rotating part as in motors and generators, but still they produce the sound because of Magnetostriction Effect which occurs inside the transformer.

Now you would ask - what is magnetostriction effect? well magnetostriction effect is one of the important property of ferromagnetic materials. Due to this property, whenever a ferromagnetic material comes in contact of varying magnetic field, it changes its dimensions.

So you might have got an idea of what happens inside a transformer. Inside a transformer is nothing but magnetic core wound by a number of turns of wires on two sides. In one side, AC voltage is applied and on another side stepped up or stepped down voltage is received. Well you might be aware that AC alternates its direction after every half cycle. Due to this variation in applied voltage, Varying magnetic field is produced and these varying magnetic fields changes dimensions of the ferromagnetic material used as the transformer component and it appears as vibrations. These vibrations are the source of the noise or “hmmm...” like sound in the transformers.

Since this process can’t be stopped so the question arises is how to reduce this kind of noise. There are many ways to achieve that, one of the ways include sound insulation which can be done by:

  1. We can use cushion padding and oil barriers which can help in insulating the sound of vibration and hence it will reduce the noise appearing to the users.
  2. Insulation of sound from Ground and Air near to the transformers.
  3. Using proper innovation designs and materials like stiffeners while constructing the walls of the transformer tanks.

Some of the other ways that can be used are proper fixing and clamping of the laminations and frames of the transformers.


  1. know i know why transformers are noisy and not only that I know now how to reduce the noise from it. I have sensitive ears and I am working in a theme park . I will fix those transformers to give me peace of mind. Thanks for this.

  2. I think this is a simple reason because this have take and pass a no of voltage which are reducing noise which are offenly we are listen.T-shirt Design software

    i have a fly-back converter in that transformer making sound. when i connected load sound is increases.

  4. fly back converter transformer is producing sound when i connect a load sound is increases.


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