My dear friend,
Our respiratory system is bounded intact which makes you feel this sound. Now as you already mentioned about your visit to ENT specialist, let me give bit overview on it.
ENT, what does it mean? ENT is nothing but Ear, Nose and Throat. These all parts of our body are interconnected and that's why when we face cold weather, when ours ears are colder then in turn it affects our nose and throat. Usually when we keep our ear warm by packing then there are less chances of throat infections(which may be due to food or water).
Now point is, as these points as interconnected, you will feel such sound usually during sickness(cold, throat infection), due to pressure as already explained by Dr Nikhil. You need to worry about it.
Please do gargling to reduce your throat infection and cold, which may bring down this problem too.