The term UNPLEASANT NOISE can be summarized by two crossword solutions: DIN (3 letters) and RACKET (6 letters). DIN is a loud, continuous noise that is often irritating and unpleasant to the ear. It is usually caused by a combination of many different sounds. RACKET is a loud, harsh sound that is usually caused by a single source. It is often used to describe the sound of an engine or a machine. Both terms are used to describe a sound that is unpleasant and disruptive.