Integrated effects of urban morphology on birdsong loudness and visibility of green areas

The aim of this study is to determine how to increase birdsong loudness and the visibility of green areas in low-density residential areas by controlling urban morphological parameters. The spatial sound level distributions of birdsong at 12 sites sampled from a GIS database of Assen, the Netherlands, were simulated by noise mapping techniques and calculated using a MATLAB program on spatial sound level matrices. The visibilities of green areas are analysed and calculated by Visibility Analysis Graph in Space Syntax. Correlation analyses were conducted between the obtained data on spatial sound level indices, the mean visibility and urban morphological parameters. The results show that birdsong loudness has significant positive linear relationships with urban morphological parameters, including Building Plan Area Fraction (R2 = 0.491), Green Area Perimeters (R2 = 0.491) and Green Area Dispersion Index (R2 = 0.618), while the visibility of green area has negative linear relationships with morphological parameters, including Building Plan Area Fraction (R2 = 0.431) and Green Area Perimeters (R2 = 0.799). It has also been found that in the proximity of green areas, the visibility of green areas has a positive relationship with birdsong loudness, whereas in most areas further from green areas, the visibility of green areas has a negative relationship with birdsong loudness. Either increasing birdsong loudness or enhancing visibility of the green areas by controlling urban morphological parameters is helpful for the optimisation of soundscape design with masking effects. Bird habitats and vegetation are important ecological issues to consider for the enhancement of the roles of urban morphology.