Noise Disturbance - Baseline Level Monitoring in the Solent.
Abstract
This report provides an update on noise monitoring results from the Solent coastline, an area with thriving harbours, ports, and coastal industries that interact significantly with the marine environment. The study focuses on Special Protection Areas (SPAs) with marine components, including the Solent and Southampton Water SPA, Portsmouth Harbour SPA, Chichester and Langstone Harbours SPA, and Solent and Dorset Coast SPA. The objective is to present data on background noise levels and understand the triggers for bird responses to anthropogenic noise during the overwintering period. Nine high-activity areas, identified as hotspots for anthropogenic activity and key SPA sites, were selected for background noise surveys. The sound index LA90, which describes the sound level exceeded for 90% of the measurement period, was used to represent background noise levels. Daytime background noise levels in the study areas typically range from 43.0 dB(A) to 49.0 dB(A), with one exception in Chichester and Langstone Harbours SPA reaching 69.0 dB(A). Short-term noise monitoring results indicate that birds are more likely to respond to noise disturbance when sound pressure levels are at least 20.0 dB(A) above typical background levels. Additionally, the visual nature of noise disturbance can also trigger bird responses. Analysis of 1/3 octave frequency data from short-term monitoring suggests no obvious correlation between specific frequencies and bird responses, although sound pressure levels at each frequency generally exceed background noise levels.