Source : Webster's Revised Unabridged Dictionary (1913)

Susurrus \Su*sur"rus\, n. [L.]
   The act of whispering; a whisper; a murmur. --De Quincey.

         The soft susurrus and sighs of the branches.
                                                  --Longfellow.

Source : WordNet®

susurrus
     n : the indistinct sound of people whispering [syn: {susurration}]