An old woman decides to get a physical after a number of years.

While the doctor is examining her she mentions that over the years she has learned to fart silently and they never smell anymore. The doctor said "Ok, that's great", finishes up the exam, gives her a prescription and tells her to come back in a couple of weeks.
When she returns, she complains that her farts now smell awful.
"Good" he said. "Now that we've cleared out your sinuses let's work on your hearing."