SUA1500 buzzing on one wall outlet, not on another - power problem?

[BillP]

Hi,

Hoping this is the right place to look for help on this.

I have a SUA1500 Smart UPS which I just started using. When used in the room with my computers it makes a loud buzzing sound whenever it is plugged in, regardless if it has anything plugged into it. I switched it to another outlet in that room and it made the same sound. Then I moved it out to my living room and plugged it in there and behold it is much quieter, still a buzzing sound but I have to put my ear right next to it to hear it and I assume that much is normal.

Going from these observations I would say there must be an issue with the power in the computer room. What could it be that is causing this though, and what could be done to correct it? The buzzing was loud enough to be distracting and made me turn it off after a few hours. I haven't had any power related issues with anything else currently used in this room.

[BillP · Accepted solution]

Follow-up, I did some reading and found that dimmer switches can cause the loud transformer buzzing because of asymetrical voltage. It just so happens that this room had a dimmer switch (which I never used and always had it set to the highest level.) I replaced it with a regular light switch and the buzzing has went away.