Yes. Normal to me.
Hi. I have the air. It happens sometimes with my too. I believe it comes from the hinges. Now, i know its not supposed to happen. But my old macbook pro did the same thing. If its really loud I would ask for an exchange. But if it is quiet, I would not worry. Exchanging for a small problem, you might get a worst one with a different problem. No electronic device is perfect. I owned few laptops. And they all had some small thing... either misaligned lid, noisy fan, noise in hinges etc... VERY hard to find one that is perfect.