The Collaborative International Dictionary of English v.0.48:

Whispering \Whis"per*ing\,
   a. & n. from Whisper. v. t.
   [1913 Webster]

   Whispering gallery, or Whispering dome, one of such a
      form that sounds produced in certain parts of it are
      concentrated by reflection from the walls to another part,
      so that whispers or feeble sounds are audible at a much
      greater distance than under ordinary circumstances. The
      dome of the U. S. capitol building is one example.
      [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

whispering dome
    n 1: a space beneath a dome or arch in which sounds produced at
         certain points are clearly audible at certain distant
         points [syn: whispering gallery, whispering dome]