Cao and Kang investigate sound not as environmental nuisance but as a constituent of social possibility. Using Peace Gardens in Sheffield, they construct four 360-degree soundscape conditions that vary the prominence and type of human sound, then evaluate them through soundscape-quality measures and willingness for social interaction. Affordance Theory provides the conceptual mechanism: acoustic conditions are assessed according to both their suitability for social activity and their capacity to stimulate interaction. The key result complicates the assumption that quieter space is automatically more sociable. Foreground human sound can increase both suitability and stimulation, whereas other conditions distribute these qualities unevenly. Demographic and companion-group differences further show that acoustic preference is socially situated. The study bridges environmental acoustics, environmental psychology and public-space design by making sociability measurable as an auditory affordance. Its broader contribution is to recast urban sound as relational infrastructure: conversations, voices and eventfulness actively configure how public space invites encounter rather than merely forming a background to visual urbanism.