Associations of soundscape naturalness and natural-element complexity with short-term psychophysiological restoration in campus green spaces: a virtual reality study.

Sustainable campus development increasingly requires outdoor environments that support both environmental quality and student wellbeing. Yet campus green spaces are commonly evaluated through visible greenness, while the combined roles of natural visual structure and soundscape naturalness remain unclear. This study integrated natural-element fractal dimension (NEFD) and the Green Soundscape Index (GSI) to assess short-term psychophysiological responses to campus green spaces. Seventy-three audiovisual scenes were collected from 10 campuses in Suzhou, China, and nine representative NEFD-GSI conditions were selected for a repeated-measures virtual reality experiment. Forty students were recruited, with valid data from 35 participants. Visual-only and audiovisual exposures were evaluated using subjective ratings, eye tracking, electrodermal activity, and cardiovascular indicators. Across the nine sampled scene conditions, response differences were most consistently aligned with the GSI dimension; for pupil diameter, the omnibus GSI-related contrast was substantial, F(2, 578) = 241.15, q < 0.001, partial η 2 = 0.455. NEFD-related differences showed a non-monotonic and soundscape-dependent pattern, with medium-NEFD conditions showing favourable tendencies under medium and high GSI; under medium GSI, the low-medium NEFD pupil-diameter contrast was 0.452 (95% CI [0.352, 0.552], Tukey-adjusted p < 0.001). Electrodermal effects were more selective, whereas most cardiovascular indicators showed limited differentiation. These findings describe sample-specific response differences among nine Suzhou campus scene conditions and do not establish generalisable effects attributable independently to NEFD or GSI; the identified numerical ranges should not be interpreted as universal design thresholds.