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

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.

Antarctic icebergs: A significant natural ocean sound source in the Southern Hemisphere

“…Prior to this event, long-term noise levels in the Pacific (EEP-NW) and the regional iceberg volume were both increasing, but the trends are too subtle to determine a robust relationship between the two time series. It is not clear if the iceberg volume in the Pacific-Antarctic region would have contributed to the noise leveling or decreasing as recently observed in the midlatitude of North American West Coast [Andrew et al, 2011], where shipping and local seasonal winds are considered to be the dominant low-frequency noise sources. The distance from 60 S to the North American West Coast hydrophones is only 15 % larger than the distance to the EEP-NW.…”

“…Interestingly, along the North American West Coast, Andrew et al [2011] show the same low-frequency noise seasonality with a few decibel of dynamic range and a wideband spectrum consistent with the characteristics of ice-generated noise observed at high southern latitudes [e.g., Dziak et al, 2013].…”

“…Archived acoustic recordings of the northern Pacific Ocean indicate an increase in ambient noise of 10-12 dB in the 25-50 Hz frequency range since the 1960s [e.g., Frisk, 2012;Hildebrand, 2009;Chapman and Price, 2011;Andrew et al, 2011;McDonald et al, 2006] . The potential impacts of increased ocean noise on marine animals' reproduction [Lillis et al, 2013], feeding [Simpson, 2005], communication [Edds-Walton, 1997], and physiology [Rolland et al, 2012] have raised concerns about ecosystem health.…”

Coral reef soundscapes : spatiotemporal variability and links to species assemblages

“…Accordingly, passive acoustic recordings of these lower-frequency fish bands may provide a better evaluation of community assemblages. Ocean noise levels are increasing at low frequencies as a result of commercial shipping activities (Andrew et al, 2011;McDonald et al, 2006;Chapman and Price, 2011). While most of these increases are below 300 Hz, an elevated low-frequency noise floor could have adverse effects on acoustic communication in fishes and, by extension, larval recruitment to reefs.…”

“…Recordings from the north Pacific Ocean indicated that low-frequency ambient noise levels increased by approximately 3 dB per decade from , potentially as a result of commercial shipping activity (McDonald et al, 2006). More recent estimates have suggested lower but positive rates of increase in that location (Andrew et al, 2011). Similarly, in the Atlantic Ocean, recordings taken near Bermuda have suggested low but positive rates of increase in ambient low-frequency ocean noise over time (Sirović et al, 2016).…”