So I'm a freelance journalist and make podcast sometimes at home. But there is a noisy transformer on the utility pole parts not far outside of my study. I'm okay to live with it, but it becomes a hassel whenever I render my audios, because I have to edit out that electrical noise.

Why does transformer make noise?

I asked google first and found out that the noise is caused by something called "magnetostriction effect." Which means, the coils inside a transformer become magnetized when energized. As a result, these coils change their physical dimensions under the influence of an electro-magnetic field. When AC power passes through the coils, it causes the magnetizing field changes periodically. So the coil dimensions change periodically per the AC frequency, i.e. 60Hz in the US. That means the coils vibrate 60 times per second and make noise.

How do you make a noise barrier?

I soon learned that the best ways to reduce noise is either move away from the source (which in my case, not applicable), or build a barrier that deflects sound wave somehow. While I was doing research, I came across a noise reduction product designed just for deflecting sound. Despite being high-tech, its working principle is simple – use something soft to block the sound wave, like old beddings.

So I went outside the house and ran a parachute cord between a birch tree and the fence near my window. Then I dig into my storage to take out a stack of old bed sheets and blankets. I unfold and stack them on top of each other to make thick layers, then hang them on the cord. It is DONE!

It simply works because not only the beddings deflect incoming noise, but also absorb a portion of the sound wave. At the end, I also added a plastic sheet on top so the barrier becomes weather-proof.

I hope my findings may help you with your noise problems. Cheers!