First of all, try to locate the root of the problem. From what you wrote, I guess this can be your home electric wiring failing to provide the quality the energy provider is giving to your home, or a low quality of the service. You said all the plugs at your home do the same thing, so it is not an isolated problem in one room or one device, like an old computer.
How can you know which one is the root?
It's not easy to know, because you normally don't have access to the wiring out of your home, it could be illegal in some places, and also very dangerous if you don't know what you are doing. Most countries have a set of rules about the quality of the electric service (the name may vary, but you get the idea). If your company fails to provide a good quality of service, they should improve it or pay you for any damage this could cause. The best way to know is inform yourself about these rules and then call the company, telling them that you are having serious quality problems. They will come to your address and check it, it won't be their fault or may be the rules will not be very strict, so don't keep your hopes up about getting any money from them.
If it is your home installation, you probably live in an old house with old wiring. I have that same issue and it's not very nice. Years ago, electric wiring wasn't taken so seriously and many rules didn't apply. You might find very thin protected wires and very noisy AC signals in an old house. How old is your home electric installation? Do light bulbs last shorter than you should expect?
I am understanding that the noise is IN the transformer and not the plug itself, check if I'm right, because the first might be harmful for your equipment but not dangerous, the second can cause a fire easily.
There are two kind of noises in a transformer, humming (which can go up to buzzing) and cracking. Humming is a "natural" noise caused by electromagnetic interaction of the transformer, it should be kept as low as possible, but if you listen carefully enough, you will always hear it in any transformer. Humming might go louder if you charge the transformer too much, but this is not very common and you don't seem to be doing it. Cracking sounds happen when the transformer is not working on its design values. Design values are voltage and current (or both) at which the device is meant to work. If you go too high or even too low, you might hear some noise. This means your transformer is doing extra work and it might significantly shorten its life. The sound in the transformer is (very) rarely caused by arcs, it normally comes from the semiconductors, which are the "switches" that let the AC pass in a way it goes out as DC.
One way to make this less critic is installing some kind of filter or protecting device that guarantees the quality of the signal received by a device. This units might seem expensive, but they can save you a lot of money on the long term if they protect 2 computers, for instance.
I hope I didn't make this very long and you can now understand what's happening. Unfortunately, there's no easy way out of this kind of problem.
(Sorry about my English, it's not my first language and I usually don't use it on this field, if you find it necessary to make any corrections to any technical term I didn't find, please do is to I can learn the right word for it).