susurrus \su-SUHR-uhs\, noun:
A whispering or rustling sound; a murmur.
Still, the breeze is soothing, as is the
susurrus of the branches.
-- Michael Finkel, "Tree Surfing and Other Lofty Pleasures," The Atlantic, March 1998
He heard the
susurrus of curtains luffed by the breeze.
-- Erik Larson, Isaac's Storm
Every time she walked into the back yard, she heard the
susurrus of a white plastic bag stuck in a tree.
-- Me, for real