Question: One of the apartments in our building is situated so that part of the bedroom is over the laundry room. Consequently, some of the noise from the equipment is heard in that bedroom. On one end of the room, the noise comes through the shaft which houses the exhaust flues and on the other it's the sump pump, the pipes for which run in the wall and under the concrete floor and carry the noise. We have had insulation blown in the walls but it helps only a little. Can you suggest something to deaden the noise?
Answer: Whew! You have problems that might be difficult to solve, according to a contractor friend. You added later in your letter that your 100-gallon water heaters make a lot of noise when they turn on. He suggested inspecting the water heaters for calcium buildup; this is a common cause of noise in water heaters, especially loud crackling noises. There may be quiet sump pumps, but he wasn't familiar with a particular brand. It's possible that lubrication might reduce the noise of the sump pump.
As to insulation, you would have to use Celotex or a similar product and you probably wouldn't experience much of a noise reduction, the contractor said. Another authority says that you have to keep the noise inside the mechanical area as much as possible, but that's something you know already.