Assessing the changing urban sound environment during the COVID-19 lockdown period using short-term acoustic measurements

Abstract

The implementation of lockdown measures due to the COVID-19 outbreak has resulted in wide-ranging social and environmental implications. Among the environmental impacts is a decrease in urban noise levels which has so far been observed at the city scale via noise mapping efforts conducted through the framework of the Environmental Noise Directive. This study aims to understand how lockdown measures have manifested at a local level to better determine how the person-level experience of the urban soundscape has been affected and how these affects differ across urban space typologies. Taking London as a case study, a series of 30-second binaural recordings were taken at 11 locations representing a cross-section of urban public spaces with varying compositions of sound sources during Spring 2019 (pre-lockdown, N = 620) and Spring 2020 (during-lockdown, N = 481). Five acoustic and psychoacoustic metrics (LAeq, LA10, LA90, Loudness, Sharpness) were calculated for each recording and their changes from the pre-lockdown scenario to the lockdown scenario are investigated. Clustering analysis was performed which grouped the locations into 3 types of urban settings based on their acoustic characteristics. An average reduction of 5.4 dB (LAeq) was observed, however significant differences in the degree of reduction were found across the locations, ranging from a 10.7 dB to a 1.2 dB reduction. This study confirms the general reduction in noise levels due to the nationally imposed lockdown measures, identifies trends which vary depending on the urban context and discusses the implications for the limits of urban noise reduction.

Rapid behavioural response of urban birds to COVID-19 lockdown

“…During the lockdown, human presence and activities decreased drastically (electronic supplementary material, figure S1, table S1), being this especially notable during rush hour, which virtually disappeared [27]. During the spring in Spain, morning rush hour matches with the first hours of light, when birds are expected to be especially communicative [36,50,55].…”

“…If birds have changed their behaviour, this adaptive, flexible behavioural response must have been mediated by phenotypic plasticity. Lockdown was sudden and the environmental scenario in urban areas changed radically from one day to the next (electronic supplementary material, figure S1) [27]. This unprecedented social experiment imposed by the COVID-19 allowed us to test and support the hypothesis of the high plasticity displayed by individuals living in urban areas in order to cope with a constantly changing environment [6–8,51].…”

“…In addition to the birds’ rapid behavioural response to the anomalous environmental conditions during the lockdown, observers had certainly enhanced opportunities to detect birds during this period. Urban areas were quitter than usual [27–29], improving the chances of listening the birds [32–34,53]. Moreover, absence of people outdoors allowed for the display of shy and distrustful behaviours [6], facilitating bird observations, especially for those less singing species, as the magpie Pica pica or the yellow-legged gull Larus michahellis.…”

“…Overall, the measures have contributed to a global diminishing of human activities [24]. This abrupt and dramatic disruption of most human social and economic activities have already had quantifiable effects on urban environments by marked reductions in air pollution [25–27] and noise [28,29]. One of the most noticeable and generalized measure has been applying certain degree of population lockdown, which renders our city streets empty and virtually silent.…”

“…Since then, social restrictions were alleviated progressively until the end of June (electronic supplementary material, figure S1, table S1). As in other parts of the world, this big halt of human activities has had significant environmental effects with reduced air contamination and noise in Spanish cities [26,27]. The severity of the lockdown measures imposed in Spain, make this country especially suitable to study COVID-19 lockdown effects in urban fauna, as they enjoyed exceptionally quitter and peaceful towns and cities during many weeks.…”