This study presents a sound-triggered installation entitled ”Drifter” to explore the interactive social dynamics of modern human relationships. The key features of the ”Drifter” include an inner reaction mechanism and an outer regulation behavior for each drifter movie clip. The inner reaction for each drifter is described by a linear chasing motion whilst the outer sound inputs supporting a random Brownian motion for each drifter. The simulation results with or without sound inputs both show a variety of social dynamical behaviors includes chasing, running, marching, meandering, circling, or a stop motion. Interestingly, from a macroscopic viewpoint, we also observed some long-time behaviors include the grouping, separating, re-grouping and etc. In summary, this study shows a possible way to explore the social dynamics of human relationships by a sound-interactive installation.