Strange noise coming from my house

[jlarrison]

Tonight I was getting everything shut down to go to bed.  I was filling up my water cup in the kitchen sink and the water was good pressure, then slowed down like someone had turned on water somewhere else.   Then it went back to full stream, then slowed down again to about 2/3 of the flow then back up to the full sream and then back down, etc...  I finally turned off the water.

I was walking around shutting everything off and I heard this low creaking sound (that I had never heard before) for about 4-5 seconds and the followed by a low thud or bang.   It sounded at first as it was coming from outside, so I went outside and heard nothing.  There was some wind going, but I didn't see anything that looked like it was hitting the house or going in the wind.  BTW - the wind was on and off. 

I went back in the house and heard it again, at least 7-10 times - with varying differences between hearing the sound.    Sometimes I would hear it right after the last sound, and sometimes I would wait for 7-10 min for the sound to come back.  It always had the same sound of a low creak followed by an even lower thud.   I checked the heater and air and they both were off.   I checked the other faucets and they didn't have this strange flow issue.   I went in the basement and it sounded lke it was coming from upstairs.  I went upstairs and it sounded like it was coming from downstairs, though the noise was so low it was hard to tell where it was coming from.

The other thing, which I am not sure is associated or not, but I heard what sounded like a low fan once in awhile, though the heat and air were off.   I thought it was the computer fan, but I am not sure.  

Our house was built in the late 30's, though we put an addition on a few years ago.   I have walked all over the house checking for water leaks, for dripping, for the heater back firing or even checked the gas on the stove and the electronics in the house to make sure they were all turned off.

I am really concerned there is something wrong and I am missing it.  I am worried if I call a plumber or a contractor they are going to tell me to call Ghost Busters.  

Anyway, I could use any tips on what this noise might be.   I can't see, to find even where it is associated with.  I do know it is generally around the area where we have the main water line come in and is also in the front of the house.  When I was in the basement in the furnace room, it sounded like it was in the vents, but above them almost.

I need help!

[MrFixit246]

A couple questions--

1. Do you have forced air or a boiler? If you have a boiler is your water make-up automatic? you could have a broken boiler line that is dumping water to an unseen area.

2. Have you checked you water Heater Temperature and pressure relief yet? This could be lifting and resetting. (It is the brass thing coming out of the side of the water heater)

3. Are you on a well or city water?  Well pump expansion tank could be compromised. Causing pump to cycle on and off rapidly.

MrFixit