There is a very famous corner in Grand Central Station where you only have to whisper to hear the other person some distance away.
Known as the "Whispering Gallery," it is located on the dining concourse. If you don't believe me, stand with a friend - or lover - in opposite corners of the large arched entryway. The low ceramic arches make for brilliant acoustics. A whisper becomes a shout. Many a marriage proposal has purportedly taken place here. And no doubt alot of other less savory proposals or admissions when physical distance is required between the parties!
Image: bowery boys