The answer is murky at best. Medicare Part A does not cover the visit at all. Medicare Part B does. Here is the lingo from the current (2014) Medicare site:
Part B covers diagnostic hearing and balance exams if your doctor or other health care provider orders these tests to see if you need medical treatment. Medicare doesn’t cover routine hearing exams, hearing aids, or exams for fitting hearing aids. In 2014, you pay 100% for routine exams and hearing aids. You also pay 20% of the Medicare-approved amount for the doctor’s services for covered exams, and the Part B deductible applies. In a hospital outpatient setting, you also pay the hospital a copayment.
As complex as this answer is, my experience has been that testing your hearing is not an expensive proposition, at least in terms of insured co-pay. The visit will cost you less than $20 out of pocket in most cases. That is a very low price for a medical exam of one of your senses and very much worth doing—now. What’s the rush? Today it is understood in medical circles that a failure to treat hearing loss may result in a more rapid cognitive decline. So take the test soon.