noun
strange noise; mysterious sound
Refers to an eerie, unexplained, or unsettling sound. Often used in ghost stories, mysteries, or when describing an unidentified noise.
夜中に怪音が聞こえて、怖くなった。
I heard a strange noise in the middle of the night and got scared.
その廃墟からは時々怪音がするらしい。
Apparently, mysterious sounds sometimes come from that ruin.