(Noun) A low soft sound as of whispering or muttering; a whisper; a rustling.

In Context

“Presently our faithful blackbird will try out a splash of liquid notes in the dimmened and newly oppressive air, and then will come the first and faintest susurrus of rain, like the sound of a blind man’s fingers reading braille.”

John Banville, The Infinities, 2010.