Perception of ambiguous visual patterns changes stochastically from one percept to the other. Although many studies have investigated the temporal dynamics of perceptual alternation, what determines the temporal dynamics remains unclear. We investigated how task-irrelevant sensory stimulation alters the perceptual stability of ambiguous visual patterns. Participants continuously reported the perceived direction of an ambiguous motion stimulus ("quartet dots"), wherein two dots could be seen as moving vertically or horizontally (von Schiller, 1933, Psychol. Forsch.; Leopald et al., 2002 Nat. Neurosci.). Task-irrelevant flashes or beeps were presented with random intervals. In separate sessions, the flash and the beep were presented either in isolation (flash-only or beep-only), synchronously, or asynchronously. The results indicated that perceptual alternations tended to occur with shorter intervals after the sensory stimulations than the prediction assuming no modulation. Interestingly, the effect magnitude on perceptual stability of visual motion did not differ between flash-only and beep-only stimulation conditions. In addition, synchronous flash-beep stimulation did not increase the effect magnitude. These results suggest that the task-irrelevant sensory stimulations alter the temporal dynamics of perceptual stability for ambiguous visual patterns through a modality-independent process.