We live in a raised ranch that is relatively new, less than 10 years old. In the last couple of days, we have noticed that when the toilets stop filling after being flushed, or when the sink or shower water is turned off quickly, a pipe in the wall is making a noise that can only be described as a moaning? Sounds like the pipe might be vibrating. It is a quick noise that only lasts for about 2 seconds. If the water is turned off slowly the noise does not occur. We have two bathrooms upstairs and then one downstairs, the noise seems to be coming from somewhere near the lower bathroom.

I was curous to find out if someone else has run into this before and if so, what the problem was and what the solution to fix this was.

As a rule this noise is caused by a toiloet being misadjusted or air chambers that need recharging. The problem is caused by the ballcock kicking on when a faucet's shut off. Try this. Open the lid on your toilet and turn and off the cold water at the lavatory, do this on all toilets. Did the float ball bounce up and down? This is caused by the ballcock absorbing the shock instead of your air chambers. (more about that later) The sound you hear is the washer vibrating against the seat of the ballcock.Let's look at your toilets first. First check there linkage between the flapper and the flush lever. It should have 1/4" of play when your tank is filled. The water level should be 1/2" below the white overflow tube after the tank's filled. Next feel the flat side of your flapper. Does it have wavey edges? Do your hands come away black? Replace it if it does. . This happened in a new house some years ago. Only at night and in the early morning. They thought the house was haunted and were about to move out. I caught it in the powder room toilet. It would vibrate and the pipes in the wall would pick it up and carry it all over the house. Now for those air chambers. Back in the 60's we were required to to put shock absorbers,(air chambers) on all bath lavatorys and kitchen sinks. Over time water and condensate built up in them and they must be recharged. First turn off the house at the main house shut off valve. Then open hot and cold faucets at the farthest bathroom to prevent air lock.(This is important.) You will find under each fixture little brass or chrome valves. These are called angle stops. With a small pail held under the angle stop to catch the run off look under the handle of the stop and you will see a nut with the stem running through it. This is called the bonnet packing nut. Put your wrench on it and back it off counterclockwise. Now open the stop and remove the stem and washer assembly, The stop will begain to drain. When it has quit draining reassemble the stop and move on to the next one. Do this on each one of your angle stops. There will be six of them. When you are done, close off the faucets you have opened, turn on the water to the house, and give yourself a pat on the back.
You have just recharged your air chambers and saved yourself a hefty service call bill. Hope this helps TOM