Well, I've had that stuff even prior to the VN stuff, because I'm a chronic allergies person, and back then before I've had any vestibular symptoms my ENT told me that it was caused by a cloughing or bad draining of the ear, due to inflamation both of the nose and the eustachian tube, wich caused that extra, undesired liquid stayed in there, causing this cracking noise.
I've also have had that extra sound sensitivity, both before and after my vestibular injury, but I've no explanation on that.