Page 33 - Spring 2018

injury or behavioral disruption focus just on the signal of interest, studies on masking must quantify ambient noise to estimate the signal-to-noise ratio, which is critical for esti- mating when an animal can detect a signal.
Standardizing Marine
Soundscape Measurements
The application of soundscape measurements in studies as- sessing the effects of human sound, mapping the distribu- tion of soniferous marine life, and understanding the role of sound in the ecology of marine life is growing and is contrib- uting to a much larger community engaged in the passive acoustic-monitoring and soundscape analysis. As a result, the community has identified a need to develop standard terminology and methods that help ensure that research and compliance measurements are repeatable and comparable across projects. International Organization for Standardiza- tion (ISO) Standard 18405 on Underwater Acoustics – Ter- minology (ISO, 2017) includes a definition of an underwater soundscape for the first time.
Underwater Acoustics:
characterization of the ambient sound in terms of its spatial, temporal, and frequency attributes and the types of sources contributing to the sound field.
Ambient sound is the sound field measured in the absence of the noise related to the measuring system. The concept of a soundscape has its roots in understanding how humans interpret the urban sound environment. The underwater acoustics definition does not include elements of perception because we cannot know conclusively how marine life inter- prets the sounds. The ISO Standard 18405 goes on to provide precise definitions of underwater acoustic terminology that will help groups exchange results using a common notation.
The ISO Standard 18405 terminology does not define how to describe a soundscape. Given the wide range of metrics and indices that may be used to describe a soundscape and the uncertainty surrounding the effects and perception of noise, arriving at consensus among researchers will take time. The Atlantic Deepwater Ecosystem Observation Network (AD- EON; https://adeon.unh.edu/) team developed three project standards, based on the ISO Standard 18405 terminology, that define the baseline metrics, data collection, and data- processing methods that the project will use for measuring and documenting the soundscape. The project team hopes
that the documents (available on the project website) will start a discussion that leads to a consensus on the minimum description of an underwater soundscape, likely through a new working group within ISO Technical Committee 43.
Ocean Sound:
An Essential Ocean Variable
Expanding efforts to measure ocean soundscapes align well with the increased focus on ocean observing systems. The Global Ocean Observing System (GOOS) was developed by the Intergovernmental Oceanographic Commission of UNESCO around three critical themes to gain a better understanding of ocean climate, ecosystems, and human impacts and vulnerabilities: (1) climate, (2) ocean health, and (3) real-time services (www.goosocean.org). The coor- dinated, long-term system of ocean observatories is built on a framework designed to be flexible, adapt to scientific in- novation, address societal needs, and deliver an observation system with a maximum user base and societal impact. The GOOS framework relates all ocean observations to EOVs to ensure measurements cut across observation platforms and represent the most cost-effective plan to provide opti- mal global coverage for each EOV. The GOOS expert panels consider EOVs in terms of scientific readiness level, societal relevance, and feasibility.
The diverse applications for information gained from lis- tening to the ocean inspired the International Quiet Ocean Experiment Program (www.IQOE.org) to propose Ocean Sound as an EOV to the GOOS Biology and Ecosystems Panel for inclusion in the GOOS network. Although ocean sound is a physical measurement characteristic of the marine environment, the Biology and Ecosystems Panel was deemed the most appropriate for submission because the majority of the ocean sound products derived from its measurement have direct or indirect biological and ecosystem applications related to the economy, food, conservation, weather, and sustainability (Table 1). Ocean Sound addresses 7 of the 10 GOOS societal pressures and all nine of the GOOS societal drivers (Table 1). The observational scale of ocean sound networks and recording platforms will allow for the study of phenomena ranging in scale from single acoustic events to long-term trends in ambient sound (Figure 6). The Ocean Sound EOV will forge major advances in our understanding of ocean soundscapes, the effects it has on marine life, and how acoustic monitoring can be used to assess biodiversity and ecosystem health.
Spring 2018 | Acoustics Today | 31