[andy jackson]

Thanks for the last answer.we have changed pressure reducers on both
Houses supplied of the same service line,since we changed the neighbors
Pressure reducer the sound is getting more frequent. The problem all
Started when the water meter was changed.The sound comes when different
Faucets are used and or commodes.

[speedball1]

This will be a process of elimination. One place to start is your toilets. Read on.
Sometimes the problem is caused by the ballcock trying to fill while water is seeping out of the tank. The sound you hear is the washer vibrating against the seat of the ballcock. 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. And last check the seat itself. Any nicks or rough spots? If so click on back. There are replacement seats that glue right over the old one and are easy to replace. One of the above should take care of your howling.

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.
One more thing. This could also happen if the ballcock kicking on every time you shut off a faucet. To check this out remove the lid and open and shut the shower valve real fast while watching the float ball. If it bobs up and down you have located the source of the problem. It is a sort of water hammer and you don't recharge your air chambers by simply draining the system. It's more complicated then that.
Let me explain. Back in the 60's we were required to to put air chambers on all bath lavatories 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 began 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 in a two bath home. 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 you out and thank you ratting my answer. TOM