Ocean ambient noise in the North Atlantic during 1966 and 2013–2014

Abstract

Low-frequency ocean ambient noise has been increasing in many parts of the worlds’ oceans as a result of increased shipping. Calibrated passive acoustic recordings were collected from June 2013 to March 2014 on the south side of Bermuda in the North Atlantic, at a location where ambient noise data were collected in 1966. Monthly and hourly mean power spectra (15–1000 Hz) were calculated, in addition to skewness, kurtosis, and percentile distributions. Average spectrum levels at 40 Hz, representing shipping noise, ranged from 78 to 80 dB re: 1 µPa2/Hz, with a peak in March and minimum in July and August. Values recorded during this recent period were similar to those recorded during 1966. This is different from trends observed in the Northern Pacific, where ocean ambient noise has been increasing; however, the location of this monitoring site was exposed only to shipping lanes to the south of Bermuda. At frequencies dominated by wind and waves (500 Hz), noise levels ranged from 55 to 66 dB re: 1 µPa2/Hz, indicating low sea states (2–3) prevailed during the summer, and higher sea states (4–5) during the winter. Seasonally important contribution to ambient sound also came from marine mammals, such as blue and fin whales.