The term 'UNSETTLING NOISE' can be summarized by the crossword solution of DIN, which is an acronym for 'duplication of input noise'. This term is used to describe a type of audio distortion that occurs when two or more signals are combined. It is often caused by the combination of multiple microphones or other audio sources in a recording environment. DIN is an undesirable effect that can make recordings sound harsh and unpleasant.