I agree and it could be any valve. Look for a valve you haven't used much but used lately. Also the gates on gate valves can break loose. You may have to close some valves off (such as the hot water heater) to try to isolate the guilty one. Also don't forget the toilet ballcocks could be bad. Opening a faucet somewhere causes a pressure fluctuation that can cause a bad one to open and pass water making the noise.