Urban park soundscapes: effects of separation distance from a busy road

Abstract

Urban green spaces, such as parks, play an important role in promoting the health and well-being of urban dwellers. Given the global trend of urbanisation and densification, city planners are faced with practical questions about the best way to distribute green space in urban areas to maximise the health benefits they bring. Among the parameters to consider is their soundscape, i.e. the acoustic environment as perceived by a person in context. This thesis presents a case study of the soundscape of a large (26 ha) urban park in Auckland, New Zealand. The research investigated the relationship between the quality of the soundscape for visitors spending time at various locations within the park at a range of distances from the kerb of a busy road. A brief soundscape questionnaire was administered to the park visitors. It included components on soundscape, self-reported noise sensitivity, and reasons for visiting the park. Observations of the visual environment, the visibility of the road at the location where the questionnaire was administered, and the ways different parts of the park were used by its visitors (i.e. functional zones) provided additional contextual data. Sound level measurements and vehicle counting were also carried out, providing objective data on the acoustic environment of the park. The results of the acoustic measurements showed that, after an initial drop by 16 dB within the first 20 metres from the kerb, most likely due to the noise abatement by vegetation and effect of the distance, the sound levels (LAeq) remained within the range of 45.3-53.3 dB throughout the park. The visual environment was characterised by a high proportion of natural elements and limited road visibility. Beyond 50 metres from the road, Nature sounds were the dominant sound source, followed by People sounds. Results of the questionnaire indicated that there was no significant difference in the overall soundscape scores between the functional zones of the park. Furthermore, the soundscape was perceived positively throughout the park regardless of the distance from the kerb. When the park visitors scored contribution of Mechanical, Nature and People sound sources to the acoustic environment, the higher contribution of Mechanical sounds (mainly the traffic noise) was associated with poorer scores given to the soundscape, regardless the functional zones. No significant effects were seen in either direction for Nature or People sounds. The functional zones reflected a broad range of activities undertaken by the park visitors: walking, playing with children, having picnics, engaging with nature, etc. These zones proved to be flexible and dependant on such factors as the traffic flow and numbers of the park visitors. The study has shown that a positive soundscape can be achieved at a variety of distances from the kerb of a road, provided the quality and size of the park permit a range of human outcomes of interest. The sound level measurement results suggested that if the size of a park permits at least a 20 m distance separation from a busy road, its environment may be more compatible with positive soundscapes for the park visitors. The finding that higher input from mechanical sounds was associated with poorer soundscapes indicated the importance of sound sources in the acoustic environment. Further research is required to investigate the effects of distance separation from the road. An adjustment in the methodology has been proposed to allow soundscape data collection at a broad range of distances, including locations nearest to the road.