Natural soundscapes enhance mood recovery amid anthropogenic noise pollution

Abstract

In urbanised landscapes, the scarcity of green spaces and increased exposure to anthropogenic noise have adverse effects on health and wellbeing. While reduced speed limits have historically been implemented to address traffic safety, their potential impact on residents' wellbeing, especially in relation to engagement with natural soundscapes, remains understudied. Our study investigates the influence of i) natural soundscapes, including bird song, and ii) the addition of traffic noise to natural soundscapes at two speeds (20 mi/h and 40 mi/h) on mood. We found that natural soundscapes were strongly linked with the lowest levels of anxiety and stress, with an increase in stress levels associated with mixed natural soundscapes with the addition of 20 mi/h traffic noise and the highest levels with 40 mi/h traffic noise. Higher levels of hedonic tone, indicative of positive mood, was noted with natural soundscapes, but diminished when combined with 40 mi/h traffic noise. Our results show that anthropogenic soundscapes including traffic sounds can mask the positive impact of natural soundscapes including birdsong on stress and anxiety. However, reducing traffic speeds in cities could be a positive intervention for enhancing access to nature. Technological solutions, such as the widespread adoption of hybrid and electric vehicles, and urban planning strategies like integrating green spaces into transit routes, offer potential opportunities to mitigate the impact of noise pollution and benefit humans in urban environments.

Fig 1. Schematic of experimental design, including pre-experimental playback period, where ‘trait’ measures of general mood were recorded for each participant, sections 1, 2 and 3 of the experiment (soundscape playback) and post-experimental period, where questions on demographics and other general questions were asked.

The experiment contained 3 sections, each with a stressor video and soundscape recording playback followed by questions measuring subjective current mood. Playbacks were either a natural soundscape (‘Natural’) or a mixed natural and anthropogenic soundscape, with either 20 mi/h (‘Mixed 20’) or 40 mi/h (‘Mixed 40’) traffic sounds added. Sections marked with a * were randomly rotated between the experiment sections for each participant, but stressor video order remained the same.

Fig 2. Mean (±SE) for three subjective measure scores: UWIST MACL stress and hedonic tone (hedtone) and STAI state anxiety, for three soundscape treatments, including a natural soundscape (light grey bars) and mixed natural and urban soundscapes with 20 (medium grey bars) and 40mi/h (dark grey bars) traffic noise (‘natural’, ‘mixed 20’, ‘mixed 40’).

Stress (UWIST MACL) was scored as nervous plus reverse relaxed scores and hedonic tone as happy plus reverse sad scores. Therefore, increased subjective stress and increased (positive) hedonic tone were represented by higher scores. Anxiety scores were calculated from the STAI-S scale as the sum of anxiety present items and reverse anxiety absent items scores, so that higher scores represented increased anxiety. Significance stars are presented for Tukey contrasts (. = p < 0.1, * = p < 0.05, ** = p < 0.01, *** = p < 0.001).

Fig 3. Scatterplots of three subjective measures, including UWIST MACL stress and hedonic tone (hedtone) scores and STAI-S (state) anxiety score against STAI-T (trait) anxiety scores.