A problem with gas

A funny joke about a little old lady goes to the doctor.Enjoy it: 

A little old lady goes to the doctor and says, "Doctor I have this problem with gas, but it really doesn't bother me too much. They never smell and are always silent. As a matter of fact I've farted at least 20 times since I've been here in your office. You didn't know I was farting because they didn't smell and are silent".The doctor says "I see. Take these pills 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, they stink terribly.""Good", the doctor said. "Now that we've cleared up your sinuses, let's work on your hearing".