Sounds in the Ocean at 1–100 Hz

Abstract

Very-low-frequency sounds between 1 and 100 Hz propagate large distances in the ocean sound channel. Weather conditions, earthquakes, marine mammals, and anthropogenic activities influence sound levels in this band. Weather-related sounds result from interactions between waves, bubbles entrained by breaking waves, and the deformation of sea ice. Earthquakes generate sound in geologically active regions, and earthquake T waves propagate throughout the oceans. Blue and fin whales generate long bouts of sounds near 20 Hz that can dominate regional ambient noise levels seasonally. Anthropogenic sound sources include ship propellers, energy extraction, and seismic air guns and have been growing steadily. The increasing availability of long-term records of ocean sound will provide new opportunities for a deeper understanding of natural and anthropogenic sound sources and potential interactions between them.

Long‐Term and Seasonal Changes of Large Whale Call Frequency in the Southern Indian Ocean

“…The advent of passive acoustic monitoring of the ocean in the last decades has improved our knowledge of the oceanic acoustic environment. Along with the abiotic (e.g., sea surface process, earthquakes, and volcanic activity) and anthropogenic (e.g., shipping and seismic exploration) sources, the biotic sources, and especially the marine mammal sounds, greatly contribute to this oceanic acoustic environment (Menze et al, ; Miksis‐Olds et al, ; Tsang‐Hin‐Sun et al, ; Wenz, ; Wilcock et al, ). Vocalizations of large baleen whales dominate the low‐frequency range of many recordings in various areas (Dziak et al, ; Haver et al, ; McDonald, Hildebrand, et al, ; Menze et al, ; Širović et al, ; Tsang‐Hin‐Sun et al, ).…”

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

“…Studies have shown that the distance to major ports and shipping lanes, changes in shipping routes, as well as economies and regulatory policies, may affect low-frequency noise levels [Miksis-Olds et al, 2013;McKenna et al, 2012]. Other studies suggest that the oceans may become more transparent to sound waves (noisier) in response to ocean acidification resulting from increased atmospheric carbon dioxide [Hester et al, 2008;Wilcock et al, 2014]. However, recent measurements off the North American coast indicate that noise trends have been level or even slightly decreasing since the mid 1990s despite the fact that the number and size of ships is still increasing [Andrew et al,2011;Wilcock et al, 2014] and CO 2 levels in the atmosphere are rising [Wootton et al, 2008].…”

“…Other studies suggest that the oceans may become more transparent to sound waves (noisier) in response to ocean acidification resulting from increased atmospheric carbon dioxide [Hester et al, 2008;Wilcock et al, 2014]. However, recent measurements off the North American coast indicate that noise trends have been level or even slightly decreasing since the mid 1990s despite the fact that the number and size of ships is still increasing [Andrew et al,2011;Wilcock et al, 2014] and CO 2 levels in the atmosphere are rising [Wootton et al, 2008]. This raises questions regarding how well we understand the major noise inputs into, and influences on, the global soundscape.…”

Consequences of global shipping traffic for marine giants

“…Shipping produces low‐frequency sounds that can travel many kilometers underwater, and is now the largest contributor of anthropogenic noise in the ocean (Wilcock et al . ). These low‐frequency sounds range from 5 to 500 hertz (Hz), and global shipping networks have added an estimated 12 decibels (dB) to ocean ambient noise levels over the past several decades (Hildebrand ).…”

“…), and acoustic pollution (Wilcock et al . ). Given that shipping impacts are predicted to increase as demand for international seaborne trade continues to grow, there is an urgent need for the development of effective mitigation strategies.…”