Whisper
A whisper was the sound of speaking in a quiet voice, especially, without vibration of the vocal cords.
In 2365, while talking with Data, Jean-Luc Picard told him that there was a loneliness inherent in that whisper from the darkness. (TNG: "Pen Pals")
Other objects could be said to make a whispering sound as well, such as flitterbird wings. (DS9: "Profit and Loss")