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Map of the week – Underwater noise indicator

Map of the week – Underwater noise indicator

The seas and oceans are not a quiet place. Under water, sound travels up to 5 times faster and 60 times further than in air, resulting in a constant background buzz of both natural and man-made sounds, called ambient noise1. The natural sounds are caused by waves, wind, rain and even earthquakes. Furthermore, marine mammals have evolved to use sound for communication, navigation and detection of predators and prey. Humans are also producing underwater sound and ambient noise levels have increased greatly since the advent of motorized ships and the use of sonar for navigation. In addition to these continuous sources of noise, human actions such as pile driving for offshore construction, seismic surveys for oil and gas exploration and underwater explosions cause high volume, short duration sound bursts called impulsive noise2. Although the impacts of this noise on marine life are not well understood, it is likely to have adverse effects, which may range from disrupted behaviour and physiological stress to hearing loss and even death.

As part of its Marine Strategy Framework Directive (MSFD), the European Union aims to monitor and limit impulsive noise to a level where it is not harmful to the marine environment3. The map of the week features the monitoring of low and mid frequency impulsive noise, expressed as pulse block days per area of 1/3° longitude by 1/6° latitude. It represents the number of calendar days during which impulsive noise was registered in each area. Notice the many noise hotspots in the Mediterranean Sea which occur near harbours and oil drilling platforms4. While the noise in the northern North Sea mainly resulted from seismic surveys, the southern North Sea noise originated from explosions and pile driving for wind farm construction2.

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The data in this map were provided by EMODnet physics.





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