Hi, my son suffers from severe ear infections. He had tubes in his ears and they have removed them already. When swimming, he always wears ear plugs to protect him from the water. (He does not have swim ears). Yesterday we went swimming and he did not have his ear plugs. Today I noticed that when he puts a finger in his ear and shakes it, there is a whistling sound that comes from there. He's not in pain but he says it bothers him. What could it be??