My classroom is located on the second floor of an old building with bare floors and thin walls. The softest of steps resonate below. Chairs scrape ... the sound is similar to elephants stomping (not that I've experienced living with elephants, but you get the picture). To protect the ears of the young and the sanity of the old(er), our chairs wear tennis balls, cut to fit over the feet. As the year progresses, chairs lose their tennis balls. They are eventually replaced, though often not for several days or weeks.
Lisa is in the classroom next door to mine. Her situation is exactly the same. Several weeks ago, her students were particularly loud. She asked them to write letters of apology to the class below. They did. Sufficiently apologetic, her kids had several reasons for their noisiness that day. My favorite is in quotes below:
"I'm sorry we were so loud, Ms. M. It's because our chairs have no balls."
Just makes you want to wait an extra few days to replace those ... balls, doesn't it?