The term white noise refers to a broadband tone, i.e. a noise with a wide and unspecific frequency spectrum. In contrast to normal warning sounds with a clear frequency, broadband tones can be up to 5 dB quieter than a beep tone at a subjectively equal perceived volume. They are usually easier to localise because they are reflected back less strongly by reflective surfaces. At the same time, a broadband tone disperses more quickly than a conventional beep, so that it can be used locally.