Long-time trends in ship traffic noise for four sites off the North American West Coast

TLDR

Measurements from 1994–2007 using four cabled‑to‑shore hydrophone systems off the North American west coast enabled comparison of contemporary low‑frequency ship‑traffic noise (25–50 Hz) with data from 1963–1965 collected with the same equipment at the same sites. The data show a roughly 10 dB increase in 25–40 Hz noise at one site, corroborated by corrected measurements from the other three systems, and linear trend lines indicate that recent levels are slightly increasing, stable, or decreasing, confirming Ross’s prediction that the rate of noise growth would be far lower at the century’s end than in the 1950s–60s. Reference: Res.

Abstract

Measurements (1994–2007) from four cabled-to-shore hydrophone systems located off the North American west coast permit extensive comparisons between “contemporary” low frequency ship traffic noise (25–50 Hz) collected in the past decade to measurements made over 1963–1965 with the same in-water equipment at the same sites. An increase of roughly 10 dB over the band 25–40 Hz at one site has already been reported [Andrew et al., Acoust. Res. Lett. Online 3(2), 65–70 (2002)]. Newly corrected data from the remaining three systems generally corroborate this increase. Simple linear trend lines of the contemporary traffic noise (duration 6 to 12+ years) show that recent levels are slightly increasing, holding steady, or decreasing. These results confirm the prediction by Ross that the rate of increase in traffic noise would be far less at the end of the 20th century compared to that observed in the 1950s and 1960s.