Until the two of us can afford to have central a/c installed in our home, we have to get by with numerous window cooling systems. It’s better than nothing, of course, but they can be certainly noisy. First, there’s the hum of the fan during ordinary operation. Then when the compressor comes on, there’s a thunking noise. Until I got used to it, every time the compressor in our study room switched on, the thunk would wake me up! And every so often, I have had to adjust the fitting in the window because a rattling noise occurs. Occasionally, when I get around to it, I’ll thumb through the owner’s manual and stumble upon an item that I overlooked when installing the cooling systems. For one thing, I found that you should pay special attention to any gaskets, as shoddy installation can lead to a recurring rattling noise. Also, any vibrating noises might be linked to poor tightening of the mounting screws. Or rattling may result from the glass panels in the window, which can be eliminated by applying window putty. Occasionally there are noises coming from inside the unit. The manual recommended that I check the mounting parts for official tightening, or that I slightly reposition the device itself. A friend of mine who works in the Heating and Air Conditioning Industry once mentioned that if the fan blades get dirty, it will cause them to get out of balance. Once this occurs, it wears out the bearings. In the end, I realize that some of my existing window cooling systems are getting older. This explains why my units are noisier than the newer models. All these things remind me to keep saving my pennies so one day I can afford central a/c for my home.