Analysis and interpretation of variability in soundscapes along an urban–rural gradient

Urbanization has not only altered land cover types, but also changed acoustic environments to which animals must adapt or emigrate for effective communication. Although many studies have addressed the effects of urban noise on acoustic communication of vocal organisms, little work has been done to understand the acoustic characteristics and the interaction between biological and anthropogenic sounds across urban–rural landscapes. The objectives of this study were to investigate the spatial and temporal patterns of soundscape characteristics along an urban–rural gradient, and how soundscape properties are related to avian species community. We established 17 locations across the city of Lansing, Michigan from February to December 2006 to record environmental sounds. A multilevel regression model (MLRM) was used to understand the variability of acoustic power of biological and anthropogenic sounds (biophony and anthrophony) with temporal and spatial data structures. Canonical Correspondence Analysis (CCA) was employed to investigate how bird species respond along an environmental gradient.We found that soundscape characteristics were associated with the structure and composition of urban–rural landscapes. Biophony was inversely correlated with anthrophony along an urban–rural gradient. The results of the MLRM showed that the acoustic variability of biophony and anthrophony were associated with landscape attributes. The CCA revealed that the distribution of bird species was significantly related to the percent area of different land cover types. The study suggests that recording acoustic characteristics in urban systems can offer opportunities to not only measure ambient noise levels, but also understand how each component of soundscape is related to another.

► We use a multilevel regression model to understand the variability of soundscapes.
► Soundscape characteristics are associated with an urban–rural gradient.
► The variability of biophony and anthrophony is associated with landscape attributes.
► The correlation of biophony with bird species implied that biophony not only reflects biological acoustic energy, but might indicate the variability of bird community structure.