Page 34 - Spring 2018

Exploring the Ocean Through Soundscapes
Table 1. Ocean Sound essential ocean variable information
Table 1. Ocean Sound essential ocean variable information
Subvariables
Sound pressure and Particle motion
Derived products
Sound field and trends, Sound pressure levels, Spectrum levels, Band levels (e.g., octave band), Soundscape, Source levels, and Biodiversity indicators
Supporting variables
Societal drivers
Sources: Distribution and characteristics of anthropogenic, abiotic, and biotic sources
Propagation parameters: Sound speed profiles; Ocean currents and other physical oceanographic phenomena; Boundary conditions (e.g., sea surface roughness, sea ice characteristics \[e.g., roughness and thickness\], and seafloor \[bathymetry, geoacoustic properties\]) Receivers: Hydrophone sensitivity as a function of frequency and directionality of the receiving system
Societal pressures
(1) Need for scientific knowledge and data access, (2) Sustainable economic growth and development, (3) Conservation of biodiversity and ecosystems, (4) Sustainable use of biodiversity and resources in general, (5) Environmental quality and health, (6) Capacity building and technology transfer, (7) Food security, (8) Threat prevention and impact mitigation, and (9) To improve management through an integrated ecosystem approach
(1) Climate change, (2) Ocean acidification, (3) Extreme weather events, (4) Loss of resources (habitats and biodiversity), (6) Mining, (9) Noise, and (10) Coastal development
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Future Outlook
There has been a substantial amount of progress in the study and application of underwater soundscapes in the past decade, but there is still a significant gap in applying the perceptual construct of underwater soundscapes to marine life in terms of masking and sense of community space as reflected in the human soundscape literature. The challenge of integrating the perception into underwater soundscape applications mir- rors that of terrestrial soundscape colleagues who are grap- pling with soundscape perception in wildlife. We will likely never understand perception across all of the animal taxa to fully identify and quantify their experience of the underwater and terrestrial soundscapes. A tractable step forward will be to better understand the hearing capabilities and variability across individuals and species and in terms of context linked to age, gender, previous noise exposure, and behavioral state. This is a lofty endeavor because there are diverse sound de- tection organs employed underwater, e.g., mammalian ears similar to ours, otolith organs in fish, and statocyst organs in invertebrates. This knowledge is critical to appropriately weighting soundscapes of different animal groups to assess effects related to sound exposures or the changing acoustic environment.
It is also important to make clear that this article does not directly address the particle motion component of sound in the soundscape. We recognize, however, that this is an incredibly important component of the soundscape for a
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Figure 6. Top: observational scales of Ocean Sounds essential ocean variable (EOV) recording platforms. Passive-recording sensors range in size and recording capabilities from small, short deployment tags attached directly to animals to freely drifting autonomous sensors of intermediate capability to large-scale observatories with sensors cabled directly to the shore for long-term recording capabilities. Bot- tom: acoustic phenomena to be captured by the Ocean Sound EOV range in scale from single acoustic detections of a passing ship or un- derwater earthquakes to long-term trends in ambient ocean sound over decades. Ocean Sound supports the derivation of metrics and acoustic indices estimating ecosystem biodiversity, the abundance of singing whales, and the effects of environmental change at the indi- vidual and population level.
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