susurration (n.)

"a whispering, a murmur," c. 1400, from Latin susurrationem (nominative susurratio), from past participle stem of susurrare "to hum, murmur," from susurrus "a murmur, whisper," a reduplication of the PIE imitative *swer- "to buzz, whisper" (source also of Sanskrit svarati "sounds, resounds," Greek syrinx "flute," Latin surdus "dull, mute," Old Church Slavonic svirati "to whistle," Lithuanian surma "pipe, shawm," German schwirren "to buzz," Old English swearm "a swarm").