Acoustic Quality in Urban Environments (SALVE) – preliminary results on the distribution of acoustic environments in an urban area

Limited research deals with acoustic environments and their opportunities for health. Little is known about the prerequisites for achieving high acoustic quality in urban environments. In our study SALVE, we investigate acoustic environments in defined urban areas. The acoustic environment encompasses biophonic (low acoustic frequencies produced e.g. by animals), geophonic (created by physical processes, like wind or rainfall) and anthrophonic sounds (including sounds from stationary or mobile machines e.g. cars).

We recorded sound at 23 specific locations in Bochum by Direct Aural Procedure (DAP) with SM2 audio device (NTi) for five minutes measuring decibels, frequency, and time. To analyse the characteristics of urban acoustic environments, we calculated acoustic indices using R studio: Acoustic Complexity Indicator (ACI), Normalized Difference Sound Index (NDSI) and LAeq values. For instance, the NDSI reflects the variability of the registered biophonies intensities, despite the presence of constant human-generated-noise.

Results show the variety of acoustic quality over space and time within different land use types. Further, we will describe the associations between the acoustic complexity, noise levels and land use types (park, residential, road). For example, areas with different sources of sound but also with higher biophonic sounds show a higher acoustic complexity. Overall anthrophonic sounds dominate over biophonic sounds however; we could observe distinct open spaces with lower anthrophonic disturbances.

Beyond noise indices, further knowledge on acoustic indices is needed. For urban public health, it is important in the future to identify the benefits that people can derive from environments of high acoustic quality.