a soft, whispering or rustling sound; a murmur
(also susurration) This word comes from Marilynne Robinson’s Gilead: “That mention of the sound of a seashell reminds me of a couple of lines of a poem I wrote once: Open the scroll of conch and find the text / That lies behind the priestly susurrus. …I have loved the word ‘susurrus‘ for a long time, and I had never found another use for it.”