Many marine organisms, from invertebrates to marine mammals, produce sounds either intentionally for communication, territory defence, mate choice, etc. or unintentionally, as a side effect of a movement or behaviour. In general, the range at which sounds can be detected, varies as a function of their acoustic characteristics (e.g., intensity, frequency). A scallop for instance, can be heard at a few meters, whereas a snapping shrimps at several hundred meters, and a blue whales at several hundred, even thousands of kilometres.
Besides biological sounds, underwater soundscapes also provide information on other natural events, such meteorological conditions (ses state, wind, rain…), sea ice cover, and earthquakes.
Last but not least, major sources of marine underwater seacapes are human activities such as shipping, construction, military exercises, etc. These sounds are often intense, low in frequency and can therefore propagate over very long distances. This is why marine anthropogenic noise is among the qualitative descriptors to be monitored and evaluated within the European Marine Framework Strategy Directive (MFSD, descriptor 11).