The combined effects of noise, nightwork and meals on mood.

The present paper describes a laboratory study on the acute effects of a combination of noise and nightwork on subjective mood. Subjects tested in the presence of noise felt more alert than those tested under quiet conditions. Circadian variation in alertness was also reported, but the noise did not change the shape of the alertness rhythms. The only exception to this was found after the mid-shift meal. Subjects tested under quiet conditions felt less alert after the meal than before it, whereas those tested in the presence of noise reported that they were more alert in the post-meal period. These results suggest that noise and nightwork produce independent effects, whereas noise and meals influence similar mechanisms.