The quality of audio-visual services is largely influenced by the qualities of the auditory and the visual signals. Perception of both signals is integrated and a single audio-visual rating is formed. The integration function depends, however, on the type of application. In this paper, we compare different integration functions which have been determined from empirical data collected in human-human and human-machine scenarios with different degrees of interactivity. The results show that the impact of each modality depends on both, the type of scenario and its degree of interactivity.