Joke: gas problem

A little old lady goes to the doctor ... and says, "Doctor, I have this problem with gas（屁）, but it doesn't really bother me too much. They never smell and are always silent. As a matter of fact, I've farted（放屁） at least 20 times since I've been here in your office. You didn't know I was farting because they don't smell and are silent." The doctor says, "I see. Here's a prescription. Take these pills 3 times a day for seven days and come back to see me next week." The next week the lady goes back. "Doctor," she says, "I don't know what the hell you gave me, but now my farts ... although still silent... stink（发臭） terribly." The doctor says, "Good! Now that we've cleared up your sinuses（your sinuses are the spaces in the bones of your head that are connected to the inside of your nose，这里指嗅觉）, let's start working on your hearing."