whispery
Soft and breathy, like a quiet whispering sound.
Whispery describes a sound that's soft, hushed, and breathy, like a whisper. A whispery voice is so quiet you have to lean in close to hear it. When someone speaks in a whispery tone, they're using very little air and their vocal cords barely vibrate, creating that distinctive hushed sound.
You might describe a singer's voice as whispery if they sing softly and breathily rather than powerfully. The rustling of leaves in a gentle breeze can sound whispery. So can the soft turning of pages in a library, or the light patter of rain just beginning to fall.
The word captures that particular quality of gentleness and quietness. A whispery sound has that specific breathy, rustling character that reminds you of actual whispering. When an author writes that a character spoke in a whispery voice, you can practically hear how soft and delicate it sounds, like they're sharing a secret or trying not to disturb someone sleeping nearby.