Annoyance is one of the most studied reactions to noise. Nevertheless, little is known about the effect of the simultaneous occurrence of noise from different sources. Existing models which predict annoyance resulting from combined noise sources are derived from results for single sources and have not yet been validated. The present study empirically investigates actual annoyance as caused from different combinations of road and rail noise in a laboratory experiment. 72 volunteers were exposed to different noise scenarios consisting of combinations of road and rail traffic noise. During noise presentation, test persons had to carry out a task on a personal computer. After each noise scenario, they had to rate their subjective annoyance. A statistical model is derived from the resulting data set, which describes the relationship between noise exposure, task difficulty and annoyance.