Searching a visual display in intermittent noise

Abstract An experiment was carried out to investigate the possible effects of auditory distractions when the visual task was to search a display in which random numbers were presented at a rate of five per second. A circle round any number was an instruction to the observer to cross off repetitions of that number, changing to a new one whenever another circle appeared. There were three auditory conditions: (a) brief bursts of noise at 110 dB SPL, (b) bursts at 70 dB, (c) always quiet. (b) and (c) were alternative experimental controls. It was found that the number of errors in the whole of a 15-min search did not differ between the three conditions, but searching was less efficient in the half-minutes following the bursts at 110 dB compared with the same periods in either control. The errors which occurred more often in loud noise were of a particular type: failure to notice the circles. It is suggested that noise increased the observer's general level of activity, enlarging differences which the need to monitor two unequally occurring features of the display, circles and numbers, had already established.