The influence of natural features and height-to-width ratios on psycho-physiological responses to urban street canyons

This study investigated the impact of natural features on the perception of urban street canyons through laboratory experiments. Wide street canyons with three different height-to-width ratios (H/Ws: 0.5, 2, and 4) were simulated, both with and without natural features such as trees, flowers, water features, and birdsong. Sounds were presented through headphones, and visual scenes were presented via a head-mounted display in a virtual reality environment. Participants assessed perceived enclosure and pleasantness to various scenarios, while monitoring and physiological responses (facial electromyography in zygomatic major (ZM) and corrugator supercilia (CS)). Results showed that H/W played an important role, with higher H/Ws generally increasing perceived enclosure but decreasing perceived pleasantness. The influence of H/W was more significant in the combined audio-visual session. It was also found that natural features significantly influenced psychological and physiological responses. In both visual-only and combined audio-visual sessions, the addition of natural features, particularly trees and birdsong, increased perceived pleasantness and fEMG ZM activity, indicating positive emotional responses. The findings suggest that urban street canyon designs need to consider H/W and the integration of natural features, especially trees and birdsong, to enhance perceived pleasantness and evoke positive emotions.