problem with loud high pitched screech

I do not know what is going on. It seems to only happen at night. One time it happened at 3PM and its getting worse. Its not happening about every 3-10 minutes. There is a loud high pitched screech that seems to come from the wall near my bathroom. its hard to tell.
i thought it was the pipes so i turned off the main water valve and this did not improve anything. I do not know why it doesn't happen during the day. The screech lasts about 1 second, but recurs.
any idea?
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to be a little more specific. the noise sounds metallic.

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any day now, you'll probably notice, you' ve entered the twilight zone

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Ryan wrote:

Owls?
--
Joseph Meehan

26 + 6 = 1 It's Irish Math
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Ryan wrote:

probably leaking a tiny bit and the toilet needs to refill every once in awhile, your 3-10 minutes. Start replacing parts in the fill line back to the wall if need be.
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On Wed, 29 Dec 2004 00:32:42 -0500, "Ryan"

Could it be a pump or fan motor in your heating system?
Steve B.
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