In dark ocean waters, fish and marine mammals such as whales and dolphins rely on sound to communicate with each other, locate prey and find their way over long distances. All these activities, critical to their survival, are being interfered with by the increasing levels of man made noise.

Underwater noise from human activities is becoming a concern and recently noise as a pollutant has received considerable attention. Airborne noise exposure has been shown to have harmful health as well as psychological influence on people. Similar detrimental health effects also affect life in the sea. Underwater noise is an increasing environmental problem.

DNV has as of 1. January 2010 issued a new voluntary class notation, SILENT. This is the first set of rules for underwater noise emission from vessels. The intention of the notation is to provide owners of acoustically sensitive vessels with concise and realistic criteria to underwater noise emission and also to provide environmental conscious owners with an opportunity to demonstrate a low environmental “footprint”.

Vessels such as offshore survey vessels, seismic vessels, fishing vessels and research vessels rely on a controlled underwater noise emission in order to perform their tasks proficiently and effectively. Other vessels and in particular cruise vessels may need to demonstrate a controlled noise emission. This is particularly relevant when moving into environmentally sensitive areas.

Fish and marine mammals such as whales and dolphins rely on sound to communicate with each other, locate prey and find their way over long distances. All these activities, critical to their survival, are being interfered with by the increasing levels of noise from ocean-going ships, sonar devices and seismic exploration. Sound travels nearly five times faster in water than in air and will cover large areas in seconds. Scientists have become increasingly aware of this threat to biodiversity, and some rate underwater noise pollution as the next global treat after climate change and chemical pollution.

DNV has over the years acquired considerable experience on underwater noise control and on underwater noise measurements. This experience has been incorporated in the SILENT criteria, but can also be used for advisory services to clients requiring help in achieving moderate underwater noise levels.

Through the SILENT notation, DNV has taken a proactive approach. SILENT will act as a safeguard against excessive noise radiation.