When human subjects assess the quality of multimedia data, high level perceptual processes such as Focus of Attention (FoA) and eye movements are believed to play an important role in such tasks. While prior art reports incorporation of visual FoA into objective quality metrics, audio-visual FoA has been rarely addressed and utilized in spite of the importance and presence of both audio and video information in many multimedia systems. This paper explores the influence of audio-visual FoA in the perceived quality of standard definition audio-visual sequences. Results of a subjective quality assessment study are reported, where it is shown that the sound source attracts visual attention and thereby the visual degradation in the regions far from the source is less perceived when compared to sound-emitting regions.