The Big Apple's Mayor Ed Koch loves to talk and his voice is rarely drowned out, but in some cases he just isn't loud enough. The city Sanitation Department has been using a recording of the mayor on its trucks to get motorists to move illegally parked cars, but says the tape just didn't have enough volume. So it was adjusted in a sound studio and now booms loudly enough to summon even drivers who are in a store. "This is Ed Koch, your mayor," the recording bellows. "You know the Sanitation Department can't sweep the street if you don't move your illegally parked car. Puh-leeze! Get it out of here!"