Exploring relationships between qualitative attributes of urban greenery and soundscape quality assessment: A case...

Soundscape, defined as the acoustic environment as perceived or experienced by humans, has gained increasing attention due to concerns about the health impacts of urban noise. A key focus of recent audio-visual soundscape studies is the role of greenery in enhancing soundscape perception. Thus far, studies have primarily concentrated on the quantity of greenery, while much less attention has been given to its qualitative attributes such as species composition, spatial configuration, color, and aesthetic qualities. Moreover, existing work often relies on linear assumptions, potentially overlooking nonlinear relationships between environmental exposure and human responses. We addressed these knowledge gaps through two soundwalks in residential neighborhoods in Singapore involving 118 participants, with acoustic recordings and 360-degree photographs collected to characterize the acoustic and visual environments. Linear mixed-effects models (LMMs) and generalized additive mixed-effects models (GAMMs) were compared to examine relationships between visual landscape attributes and soundscape assessments. The results showed that GAMMs outperformed LMMs, indicating improved performance when nonlinear effects were considered. Landscape attributes, including wildness, visual depth, sky view index, and building view index, were found to be significantly associated with soundscape perception, with nonlinear relationships identified for wildness and visual depth. A turning point at 0.6 was observed in the relationship between wildness and soundscape quality, beyond which increases in wildness were associated with greater increases in soundscape quality. Sensitivity analyses confirmed the robustness of these findings. Overall, this study highlights the importance of moving beyond a sole focus on greenery quantity to consider its qualitative characteristics in soundscape research, thereby advancing understanding in this field.