Here’s a fun tip for visitors to (or even residents of) NYC. If you’re in Grand Central, make your way down to the lower level where all the food is and find the Oyster Bar. In front of the entrance is an archway about 12-16 feet across. If you and a companion stand facing opposite walls of the arch just inside the archway and whisper to each other, you will be able carry on a hushed conversation despite the 15-foot gap between you. The closer you get to the wall the better…about 6-12 inches away is pretty good. This works on the same principle as the “whisper dishes” you see at science museums.