The "Whispering Gallery" in Grand Central Terminal is an acoustic phenomenon. If you whisper into one corner of the arched hallway, someone on the opposite side of the hallway can hear you as if you're speaking right next to them. We've tried it - it works. Try it yourself, then head over across the hall to The Oyster Bar for some delicious grub. If you sit at the middle counter and you get a tiny Asian woman as your waitress, say hi - she's my aunt!