The effects of background sounds on cognitive performance are of great relevance to the study of efficiency in work environments such as offices and flight deck, where the presence of extraneous auditory stimuli is common. A number of laboratory studies have shown large and consistent disruption of performance, despite participants' consciously trying to ignore the task-irrelevant sounds. This breakdown of selective attention suggests that unattended sound is processed to some extent and that this process interferes wwith processing task-relevant information. The features of the sounds and those of the tasks, which augment and reduce the degree of disruption, as well as the practical implications of those findings, are discussed in this rev...