noun
whispering; quiet weeping
Refers to a low, subdued sound made while trying not to be heard, such as a whisper or muffled sobbing. Often used in literary or poetic contexts.
夜中に忍び音が聞こえて、誰か泣いているのかと思った。
I heard a quiet weeping sound in the middle of the night and thought someone was crying.
彼女は忍び音で秘密を打ち明けた。
She revealed the secret in a whisper.