Irrelevant Decibels is a term used to describe the amount of NOISE that is not relevant to the task at hand. It is usually measured in decibels, which is a unit of sound intensity. The term is often used in the context of soundproofing and NOISE control, as it is important to reduce the amount of irrelevant NOISE in order to ensure that the environment is conducive to work or study. NOISE, which is the 5-letter solution to the crossword, is an unwanted sound that can be disruptive and distracting.