Use of acoustic indexes to verify the influence of high levels of anthropic noise on the diversity of species

The increase in urbanization due to the expansion of cities has reduced the diversity of species and the homogenization of bird communities. Natural areas near cities have high levels of noise, which pose great challenges for species that use sound communication. Analysis of the temporal and spatial distribution of sounds reflects important ecosystem processes and human activities. Acoustic indices are quick and practical ways to verify the characteristics of communities. The Acoustic Diversity Index (ADI) reflects the diversity of species that are vocalizing and the Normalized Difference Soundscape Index (NDSI) the ratio of anthropogenic noise to vocalizations. The objective of the study was to calculate ADI and NDSI and verify if there is a relationship between them. Were performed recordings of bird vocalizations with Marantz PDM 661 Mark II recorder and Sennheiser ME67K6 directional microphone from 06:00 to 9:00 am between April/2015 and April/2017 in 16 Brazilian Cerrado forest fragments. The indices were calculated by the SoundEcology package of the R Statistic program and performed a Simple Linear Regression to verify the interaction between the indices. Were analyzed 657 02min. stretch each, extracted from field recordings. The ADI value was 0.67±0.47 (mean±standard deviation) and NDSI of 0.52±0.33. There was a positive association between ADI and NDSI (p<0.01), so that the higher the NDSI values, the higher the ADI values. Higher values of NDSI reflect a lower amount of anthropogenic source noise and are positively related to higher species diversity (higher ADI).