You searched for: “susurrus”
susurration, susurrus (s) (noun); susurrations, susuruses (pl)
An instance or act that involves a soft rustling sound; murmuring or whispering: James and Jenny could hear the susurrus of the stream by their tent when they went camping during their vacation.
This entry is located in the following unit: English Words in Action, Group S (page 14)