Polar soundscapes

What is a soundscape?

In layman terms, a soundscape is the sound a marine animal would hear if it sits still and listens to the ocean around it.

More formally, a soundscape is the "characterization of the ambient sound [...] in terms of its spatial, temporal and frequency attributes, and the types of sources contributing to the sound field" (ISO18405, 3.1.1.3).  Ambeint sound is the "sound [...] that would be present in the absence of a specified activity" (ISO18405, 3.1.1.2).

Ambient sound is composed of natural abiotic and biotic and anthropogenic sounds. Natural abiotic ('geophonic') sounds include sound produced by wind, waves and ice movement, biotic ('biophonic') sounds are emitted by sound-producing species and man-made ('anthrophonic') sounds emanate from human activies, such as shipping, oil and gas exploration, or underwater construction work.

Our research on polar marine soundscapes adresses the following questions:

  • Which marine mammal species inhabit the polar oceans temporally or permanently?
  • How does the acoustic biodiversity of marine polar habitats change with time and space and how does it relate to other environmental and ecological factors?
  • How do natural and anthropogenic sounds contribute to the overall acoustic enviroment of an area?
  • Which role does the character and quality of (local) acoustic habitat play for marine mammal habitat preferences?

Long-term spectrogram depicting a three-year recording from the Antarctic (69°S 0°W). The x-axis shows the day of the recording, the y-axis the sound frequency. Intense sound (at the respective day and frequency) is plotted red, quiet sound in blue.

The data reveals the repeating patterns of seasonal vocalizations of Antarctic blue whales, fin whales, and Antarctic minke whales (horizontal stripes around 20 to 30 Hz, 100 Hz, 100 to 300 Hz, respectively). Abiotic sound levels are strongly affected by storms and the waxing and waning of the sea-ice cover, which, during austral winter, decouples wind from the ocean underneath (vertical striping), quieting the ocean.