Whistling noise when water running

[itcsburnett]

Im baffled and hoping someone here can help.
Every once and a while, when water is running somewhere in the house, we get a high pitched whining that is loudest in the upstairs bathroom. I thought it might be the vent stack as that is near where I hear it loudest, but explored the attic and its not the vent pipe. Opening a faucet anywhere in the house can change the pitch and if it runs hard enough can stop it altogether. Turn off that water and it starts back up again.
This started about 6 months ago. We have had no plumbing work done recently.
Anyone have any idea where to begin? I really cant call a plumber because I dont know when it will happen.

 

[frodo]

is it only when water is being used? check your toilet fill valve first.

 

[Mr_David]

I have a hummer for you .
I made this video about 4 yrs

This is an exceptionally loud example.
More often this can resonate throughout the house using the copper water lines like violin strings.
Get rid of the ball cock an use a fluidmaster.
http://www.plumbingforums.com/forum/showthread.php?t=988

 

[itcsburnett]

The noise can occur when just about anything opens a water valve. The Washer, humidifier, another faucet and yes, a toilet flushing. It just happens to be the loudest in the upstairs bathroom. And while the video I posted shows me opening the bathroom faucet, any other valve or faucet can also alter the pitch and make it stop. Could it be the pressure reducer resonating in the pipes? I dont hear it at all in the basement near the main inlet.
video for the sound: http://youtu.be/gPfbUDRRzNk

 

[Mr_David]

Thanks for the video. If you have eliminated the possibility of it coming from the toilet ballcock. It Could be the pressure reducing valve. Try adjusting it up and down while you have a faucet open. That is pretty high pitched.
The copper pipes can resonate a noise throughout the house. it can originate on the other side of the house from where you hear it the loudest.

 

[itcsburnett]

A friend suggested it sounded to him like air in the line. I followed this procedure and it seems to have solved the issue.

Now i have to ask how did the air get in there in the first place?