about one year ago during a light freeze my plumbing in the attic (cold water side) started singing anytime a cold water faucet was turned off. including the washing machine and ice maker or toilet flush. it is now december 2002 and nothing has changed. it seems if we slowly turn off the faucets it is less, but if we turn the faucets off quickly the pipes will sing for up to 20-30 seconds. this happens in any part of the house. any advise?