Mid Frequency Bottom-Interacting Sound Propagation and Reverberation in the Baltic

Pihl, J.

doi:10.2174/1874837601104010001

Cited by 2 publications

(1 citation statement)

References 14 publications

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“…The uncertainty in modeling due to an uncertain environment applies, of course, to all three areas. As in [33], bottom porosity values for modeling could be set guided by the local bottom depth and slope.…”

Section: Discussionmentioning

confidence: 99%

Measurements and Modeling of Effects of Out-of-Plane Reverberation on the Power Delay Profile for Underwater Acoustic Channels

Jenserud

Ivansson

2015

IEEE J. Oceanic Eng.

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Long reverberation tails are often observed in shallow-water acoustic channel impulse responses (CIRs). Examples from three significantly different environments along the Norwegian coast are presented. It is shown that 2-D propagation modeling fails to reproduce the long tails. Nevertheless, inclusion of the impulse response tails is necessary in connection with model-based simulators of communication performance, to avoid too optimistic estimates of bit error rates, etc. This is demonstrated by simulation examples for one of the environments, comparing results for truncated and complete impulse responses. High wind speeds and Doppler spread signals indicate that surface reverberation must be taken into account for modeling the tail energy. In bistatic scenarios such as the ones considered here, backscattering computations in a single vertical 2-D plane are not sufficient. A 3-D ray-based model, Rev3D, is utilized to include effects of out-of-plane scattering from the sea bottom as well as the sea surface. The scattering-strength functions include azimuthal variation, with significantly enhanced scattering close to the forward direction. Rev3D modeling supports the hypothesis that out-of-plane scattering and reverberation are main mechanisms behind the observed continuous, exponentially decaying impulse responses. Modeling incorporates available environmental information concerning sound-speed profiles, bottom topography and type, surface wave spectra, etc. Good agreement of measured and modeled time series is obtained for two of the locations. For the remaining location, modeling correctly recovers a significantly lower decay rate of the reverberation tail in comparison to the other locations, but the modeled decay rate is somewhat too large.

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Section: Discussionmentioning

confidence: 99%

Measurements and Modeling of Effects of Out-of-Plane Reverberation on the Power Delay Profile for Underwater Acoustic Channels

Jenserud

Ivansson

2015

IEEE J. Oceanic Eng.

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Current species protection does not serve its porpoise—Knowledge gaps on the impact of pressures on the Critically Endangered Baltic Proper harbour porpoise population, and future recommendations for its protection

Koschinski,

Owen,

Lehnert

et al. 2024

Ecology and Evolution

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Successful management requires information on pressures that threaten a species and areas where conservation actions are needed. The Baltic Proper harbour porpoise population was first listed as Critically Endangered by the International Union for the Conservation of Nature in 2008. Now, 16 years later, there is no change in conservation status despite ample conservation policy calling for its protection and an urgent need for management action to protect this population. Here, we provide an overview of the current status of the population, highlight knowledge gaps on the impact of pressures, and make recommendations for management of anthropogenic activities. Based on an exceeded limit for anthropogenic mortality, the high concentrations of contaminants in the Baltic Sea, combined with reductions in prey availability and increases in underwater noise, it is inferred that this population is likely still decreasing in size and conservation action becomes more urgent. As bycatch and unprotected underwater explosions result in direct mortality, they must be reduced to zero. Inputs of contaminants, waste, and existing and emerging noise sources should be minimised and regulated. Additionally, ecosystem‐based sustainable management of fisheries is paramount in order to ensure prey availability, and maintain a healthy Baltic Sea. Stranding networks to routinely assess individuals for genetic population assignment and health need to be expanded, to identify rare samples from this population. Knowledge is still scarce on the population‐level impact of each threat, along with the cumulative impact of multiple pressures on the population. However, the current knowledge and management instruments are sufficient to apply effective protection for the population now. While bycatch is the main pressure impacting this population, urgent conservation action is needed across all anthropogenic activities. Extinction of the Baltic Proper harbour porpoise population is a choice: decision‐makers have the fate of this genetically and biologically distinct marine mammal population in their hands.

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Mid Frequency Bottom-Interacting Sound Propagation and Reverberation in the Baltic

Cited by 2 publications

References 14 publications

Measurements and Modeling of Effects of Out-of-Plane Reverberation on the Power Delay Profile for Underwater Acoustic Channels

Measurements and Modeling of Effects of Out-of-Plane Reverberation on the Power Delay Profile for Underwater Acoustic Channels

Current species protection does not serve its porpoise—Knowledge gaps on the impact of pressures on the Critically Endangered Baltic Proper harbour porpoise population, and future recommendations for its protection

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