Parrothead, the differential diagnosis of muffled hearing after a dive has a number of things in it, ranging from trivial (water in the external auditory canal) to serious (inner ear damage). It's impossible to sort these things out over the internet.
That said, here is some basic information: Hearing depends on sound waves being able to pass through the external auditory canal (tube from the outside world to the eardrum). The eardrum must be free to move easily, to transmit the sound waves to movement of the small bones in the middle ear. These then carry the sound energy to the inner ear, where it is transduced into nerve signals to go to the brain. Anything that impedes the movement of the sound vibration through this pathway can result in muffled hearing.
Probably the single most common cause of decreased hearing after diving, particularly if it is painless and not associated with any kind of balance issues, is fluid in the middle ear as a result of late or incomplete equalization. The fluid decreases the mobility of the eardrum, reducing the transmission of sound to the inner ear. This fluid can be either simple edema fluid, sucked out of the tissues around the canal by the relative vacuum that occurs when you don't equalize well, or it can even be blood. If there is a small amount, and it is simple fluid, it will be reabsorbed fairly quickly (a couple of days, or even overnight). If there is a large amount, and especially if there is blood in it to render it thicker and more likely to coagulate, it can take days to weeks to resolve.
No specific therapy has been shown to hasten this process. Various things have been suggested, including antiinflammatory medication (to reduce tissue swelling), or decongestants (to open the Eustachian tube and allow fluid to drain that way). Even chewing gum has been suggested, as a kind of Eustachian tube orifice massage! To my knowledge, no one has ever done a study to see if any of these modalities actually changes the course of middle ear barotrauma.
Since the diagnosis list includes some more serious problems, some of which respond much better if treated promptly, muffled hearing that persists beyond a couple of days after a dive probably ought to be evaluated by a physician, preferably an ENT doc with some familiarity with diving issues.
Any ideas on what can cause this & how to treat it?
