Until we all can afford to have central air conditioning installed in our home, my roommates and I have to get by with multiple window air conditioners. It’s better than nothing, of course, but they can be really noisy. First there’s the hum of the fan under ordinary operation. Then, when the compressor comes on, there’s a thunking noise. Until we got used to it, every time the compressor in our dining room switched on, the thunk would wake all of us up! Every so often, I have had to adjust the fitting in the window because a rattling noise occurs. Occasionally, I’ll thumb through the owner’s manual and stumble upon an item that I overlooked when installing the window A/C’s. For one thing, one must pay special attention to any gaskets, as improper installation can lead to a rattling noise, and any vibrating noises might be linked to improper tightening of the mounting screws… Rattling may also result from the glass panels in the window, which can be eliminated by applying window putty. Sometimes there are noises coming from inside the unit. The manual proposed that I check the mounting parts for proper tightening, or that I slightly reposition the component itself. A neighbor of mine who works in the HVAC 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 air conditioners are getting older. This alone explains why my units are noisier than the newer models. All of these things remind my roommates and I to keep saving our pennies so that one day we can afford central air conditioning for our place.