Effect of differential levels of ambient noise on vigilance performance.

Abstract

Research has indicated that high intensity white noise may affect performance, particularly if long-term attention is required. Ambient white noise is often used in vigilance experiments in order to mask equipment and extraneous noise and/or to provide a constant background of auditory stimulation. However, an acceptable intensity level has not been established and a wide range of noise levels has been used. The question immediately apparent is whether or not noise level itself becomes a variable in these studies and interacts with other variables under investigation. If this is the case, the results are confounded, and investigators would be faced with the problem of re-examining the literature and reinterpreting the studies which do not consider this factor. The present study was a test of this question, i.e., does the intensity level of ambient white noise have any effect upon vigilance performance. Ss were 27 male undergraduate students enrolled in an introductory psychology course. Nine Ss each were randomly assigned to one of three experimental conditions: 50 db, 75 db, and 90 db ambient noise levels. S's task in all conditions was to monitor a visual display for 40 min. in order to detect aperiodic signals against a background of regularly occurring events. Forty-eight signals in a 40-min. period were presented for a signal probability of .04. The procedure and apparatus were identical to those previously reported by Halcomb and Blackwell ( 1969). A split-plot analysis of variance was used to analyze the number of errors (misses) and false alarms made by each S during each 5-min. period. The results of the analysis of variance showed a significant decrement over time for both misses and false alarms (indicating that the task was indeed measuring vigilance behavior). No significant differences were found for the three intensity levels for either misses or false alarms nor were there significant interactions between noise levels and time-on-task. Therefore, the results of this study indicate that the intensity level of ambient white noise has no significant effect upon vigilance performance.