The acoustic environment before and during the SARS-CoV-2 lockdown in a major German city as measured by ecoacoustic indices.

The SARS-CoV-2 pandemic drastically changed daily life. Lockdown measures resulted in reduced traffic mobility and, subsequently, a changed acoustic environment. The exceptional lockdown was used to analyze its impact on the urban acoustic environment using ecoacoustic indices. Using data from 22 automated sound recording devices located in 9 land use categories (LUCs) in Bochum, Germany, the normalized difference soundscape index (NDSI) and Bioacoustics index (BIO) were explored. The NDSI quantifies the proportion of anthropophonic to biophonic sounds, and BIO quantifies the total sound activities of biological sources. The mean differences and standard deviation (SD) were calculated 5 weeks before and 5 weeks during the first lockdown. Pronounced peaks for the NDSI and BIO before lockdown that diminished markedly during lockdown were observed, however, with distinct differences in terms of the LUC. The mean NDSI increased from 0.00 (SD = 0.43) to 0.15 (SD = 0.50), the mean BIO decreased from 4.74 (SD = 2.64) to 4.03 (SD = 2.66). Using the NDSI and BIO together reveals that changes of the acoustic environment during lockdown are mainly driven by decreased anthropophonic sound sources. These results suggest that further studies are needed to tailor ecoacoustic indices more accurately to conditions of the urban environment.

Impact of the COVID-19 Lockdown Measures on Noise Levels in Urban Areas-A Pre/during Comparison of Long-Term Sound Pressure Measurements in the Ruhr Area, Germany

BACKGROUND: A major source of noise pollution is traffic. In Germany, the SARS-CoV-2 lockdown caused a substantial decrease in mobility, possibly affecting noise levels. The aim is to analyze the effects of the lockdown measures on noise levels in the densely populated Ruhr Area. We focus on the analysis of noise levels before and during lockdown considering different land use types, weekdays, and time of day. METHODS: We used data from 22 automatic sound devices of the SALVE (Acoustic Quality and Health in Urban Environments) project, running since 2019 in Bochum, Germany. We performed a pre/during lockdown comparison of A-weighted equivalent continuous sound pressure levels. The study period includes five weeks before and five weeks during the SARS-CoV-2 induced administrative lockdown measures starting on 16 March 2020. We stratified our data by land use category (LUC), days of the week, and daytime. RESULTS: We observed highest noise levels pre-lockdown in the 'main street' and 'commercial areas' (68.4 +/- 6.7 dB resp. 61.0 +/- 8.0 dB), while in 'urban forests' they were lowest (50.9 +/- 6.6 dB). A distinct mean overall noise reduction of 5.1 dB took place, with noise reductions occurring in each LUC. However, the magnitude of noise levels differed considerably between the categories. Weakest noise reductions were found in the 'main street' (3.9 dB), and strongest in the 'urban forest', 'green space', and 'residential area' (5.9 dB each). CONCLUSIONS: Our results are in line with studies from European cities. Strikingly, all studies report noise reductions of about 5 dB. Aiming at a transformation to a health-promoting urban mobility can be a promising approach to mitigating health risks of noise in cities. Overall, the experiences currently generated by the pandemic offer data for best practices and policies for the development of healthy urban transportation-the effects of a lower traffic and more tranquil world were experienced firsthand by people during this time.