There is a constant noise coming from the faucet where the water flows to the icemaker. I have turned the faucet off & the noise continues; a high pitched noise. Is this air in the line or what? The refrigerator has been hooked up for 4 years, and this is a new noise. It is not the refrigerator making the noise; it is clearly from the faucet in the wall. No water leaks noted. HUH?