Emerging soundscape patterns across a gradient of land use intensity

Background/Question/Methods

Anthropogenic alterations to natural landscapes have given rise to a variety of land use intensities resulting in pollution to surrounding natural areas. Noise pollution is one of the most recent forms of disturbance to be considered for remediation.  Acoustic communication is crucial for reproductive success, survivorship, and recruitment for many species and anthropogenic noise has been shown to compromise these activities. The noise from energy intensive processes is not confined. Rather, it spreads outward, introducing background noise disturbance into neighboring ecosystems.  The Landscape Development Intensity index (LDI) measures the non-renewable energy intensity of surrounding land uses. It is considered an integrated measure of human activity, combining the impacts from pollutants, physical damage, changes in environmental conditions, etc. This study aims to utilize the LDI as an index of land use intensity to compare to the soundscapes of nearby points. A soundscape is the aggregate sounds from an environment. The Acoustic parameters used in this study to describe each soundscape were average power, the average level of sound energy, peak power, the energy level of the loudest event, and aggregate entropy, a measure of the distribution of sound energy across the frequency spectrum.

Results/Conclusions

The analyses sites (n=21) in North Central Florida ranged from low energy intensity (LDI = 0) to High (LDI = 42). Results show statistically insignificant correlations between points’ surrounding land use intensity and acoustic measures of the points’ soundscape. Even if weak, the relationships between land use intensity and acoustic parameters are logical. Land use intensity has a positive relationship with the average power and peak power of soundscapes, indicating that high energy land uses are correlated with more sound energy and louder sound events. Land use intensity and aggregate entropy has a negative relationship, showing that high energy land uses produce soundscapes with sound energy that is concentrated in a few frequency bands versus spread evenly along the spectrum. The most prominent characteristic of land use intensity found in the soundscape is a band of high sound energy in the 0-4 kHz frequency range.  Altering the calculation of land use intensity to encompass a larger area surrounding the point and weighting land uses based on proximity to the point has strengthened the relationship between soundscape characteristics and land use intensity.  These adjustments reflect sound dissipation over a landscape more accurately.