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Ocean Noise

Andrei-Emil Briciu, Dumitru Mihăilă, Dinu Iulian Oprea, Petruț-Ionel Bistricean, Liliana Gina Lazurca
An orthotidal signal is a tidal component found in a streamwater parameter when there is no oceanic tidal input, i.e. when the streamwater monitoring point is located far inland and at high elevation. This study analyses various parameters of Cib River in Carpathian Mountains, Romania. This river receives water from a rich karst aquifer when crossing Cib Gorge. Streamwater level, temperature and electrical conductivity were measured in 270 days grouped in three time intervals of consecutive days. The measurements were done every 15 minutes in order to capture any significant periodic variation...
April 15, 2018: Environmental Monitoring and Assessment
Tullio Rossi, Jennifer C A Pistevos, Sean D Connell, Ivan Nagelkerken
Population replenishment of marine life largely depends on successful dispersal of larvae to suitable adult habitat. Ocean acidification alters behavioural responses to physical and chemical cues in marine animals, including the maladaptive deterrence of settlement-stage larval fish to odours of preferred habitat and attraction to odours of non-preferred habitat. However, sensory compensation may allow fish to use alternative settlement cues such as sound. We show that future ocean acidification reverses the attraction of larval fish (barramundi) to their preferred settlement sounds (tropical estuarine mangroves)...
April 11, 2018: Scientific Reports
Hui Meng, Xiaoqing Wang, Jinsong Chong
In synthetic aperture radar (SAR) ocean remote sensing, it is very difficult to estimate an accurate azimuth antenna pattern (AAP) from low-scattering SAR images without strong scattering targets. Therefore, an azimuth antenna pattern estimation method based on Doppler spectrum in SAR ocean images is proposed in this paper. In order to preserve the complete AAP information, an azimuth unweighted matched filter is used to re-image the SAR raw data in the proposed method. Then, the shape factor of AAP can be obtained by linear statistics of the relationship between Doppler center and edge frequency spectrum in Doppler spectrum of each distance gate...
April 3, 2018: Sensors
Menghua Wang, Howard R Gordon
We analyze the effects of the sensor signal-to-noise ratio (SNR) requirements for atmospheric correction of satellite ocean color remote sensing using the near-infrared (NIR) and shortwave infrared (SWIR) bands. Using the Gaussian noise model for the sensor noise distribution in the NIR and SWIR bands, some extensive simulations have been carried out to evaluate and assess the effects of sensor NIR and SWIR SNR values on the retrieved normalized water-leaving reflectance spectra ρwN(λ), which are used to derive all ocean or inland water biological and biogeochemical property data...
March 19, 2018: Optics Express
Chris H Harrison
An expression for the cross-spectral density matrix of ocean noise naturally separates into a Toeplitz part and a Hankel part [Harrison (2017). J. Acoust. Soc. Am. 141, 2812-2820]. The Toeplitz part is shown to be substantially rank-deficient for all practical acoustic cases, which has implications for adaptive beam forming. The influence of the Hankel part on passive fathometry is investigated, and its effect on adaptive beam forming is shown to be weak or negligible. Numerical demonstrations of these findings including beam patterns and eigenvalue spectra derived via circulant matrices are given based on a simple half-space with a Rayleigh reflection coefficient...
March 2018: Journal of the Acoustical Society of America
Yalçın Ata, Yahya Baykal
Effect of anisotropy on the average bit error rate (BER) is investigated when an asymmetrical Gaussian beam is propagated in an anisotropic turbulent ocean. BER is found to decrease in response to an increase in anisotropy levels in the x and y directions. Higher average signal-to-noise ratio, wavelength, and microscale length yield smaller BER values. BER starts to rise with an increase in the asymmetrical beam source size in the x and y directions, source size ratio in the x and y directions, salinity and temperature contribution factor, the dissipation of the mean squared temperature, and the propagation distance...
March 20, 2018: Applied Optics
Haiying Gao
Significant along-strike variations of seismicity are observed at subduction zones, which are strongly influenced by physical properties of the plate interface and rheology of the crust and mantle lithosphere. However, the role of the oceanic side of the plate boundary on seismicity is poorly understood due to the lack of offshore instrumentations. Here tomographic results of the Cascadia subduction system, resolved with full-wave ambient noise simulation and inversion by integrating dense offshore and onshore seismic datasets, show significant variations of the oceanic lithosphere along strike and down dip from spreading centers to subduction...
March 23, 2018: Nature Communications
Ainsley S Allen, Harald Yurk, Svein Vagle, James Pilkington, Rosaline Canessa
Vessel traffic is one of the most wide-spread anthropogenic contributors to ocean noise worldwide and has the potential to alter ecosystems upon which cetaceans and other acoustically sensitive marine organisms rely. Canada's SGaan Kinghlas-Bowie Seamount Marine Protected Area (SK-B MPA) is one such area whose productive ecosystem could benefit from greater monitoring of human induced threats in order to inform management. Despite earning official designation as a Marine Protected Area under the Oceans Act in 2008, little remains known about vessel traffic in the region and the associated potential impacts on vulnerable marine species...
March 2018: Marine Pollution Bulletin
Mark I McCormick, Sue-Ann Watson, Stephen D Simpson, Bridie J M Allan
Oceans of the future are predicted to be more acidic and noisier, particularly along the productive coastal fringe. This study examined the independent and combined effects of short-term exposure to elevated CO2 and boat noise on the predator-prey interactions of a pair of common coral reef fishes ( Pomacentrus wardi and its predator, Pseudochromis fuscus ). Successful capture of prey by predators was the same regardless of whether the pairs had been exposed to ambient control conditions, the addition of either playback of boat noise, elevated CO2 (925 µatm) or both stressors simultaneously...
March 28, 2018: Proceedings. Biological Sciences
Farshid Mashayekhy Rad, Caroline Leck, Leopold L Ilag, Ulrika Nilsson
RATIONALE: Fatty acids are enriched in the ocean surface microlayer (SML) and have as a consequence been detected worldwide in sea spray aerosols. In searching for a relationship between the properties of the atmospheric aerosol and its ability to form cloud condensation nuclei and to promote cloud droplet formation over remote marine areas, the role of surface active fatty acids sourced from the SML is of interest to be investigated. Here is presented a fast method for profiling of major fatty acids in SML samples collected in the high Arctic (89 °N, 1 °W) in the summer of 2001...
March 9, 2018: Rapid Communications in Mass Spectrometry: RCM
Mingsong Li, Linda A Hinnov, Chunju Huang, James G Ogg
In ancient hothouses lacking ice sheets, the origins of large, million-year (myr)-scale sea-level oscillations remain a mystery, challenging current models of sea-level change. To address this mystery, we develop a sedimentary noise model for sea-level changes that simultaneously estimates geologic time and sea level from astronomically forced marginal marine stratigraphy. The noise model involves two complementary approaches: dynamic noise after orbital tuning (DYNOT) and lag-1 autocorrelation coefficient (ρ1 )...
March 8, 2018: Nature Communications
Antonio-Javier Gallego, Pablo Gil, Antonio Pertusa, Robert B Fisher
In this work, we use deep neural autoencoders to segment oil spills from Side-Looking Airborne Radar (SLAR) imagery. Synthetic Aperture Radar (SAR) has been much exploited for ocean surface monitoring, especially for oil pollution detection, but few approaches in the literature use SLAR. Our sensor consists of two SAR antennas mounted on an aircraft, enabling a quicker response than satellite sensors for emergency services when an oil spill occurs. Experiments on TERMA radar were carried out to detect oil spills on Spanish coasts using deep selectional autoencoders and RED-nets (very deep Residual Encoder-Decoder Networks)...
March 6, 2018: Sensors
Frank E Muller-Karger, Erin Hestir, Christiana Ade, Kevin Turpie, Dar A Roberts, David Siegel, Robert J Miller, David Humm, Noam Izenberg, Mary Keller, Frank Morgan, Robert Frouin, Arnold G Dekker, Royal Gardner, James Goodman, Blake Schaeffer, Bryan A Franz, Nima Pahlevan, Antonio G Mannino, Javier A Concha, Steven G Ackleson, Kyle C Cavanaugh, Anastasia Romanou, Maria Tzortziou, Emmanuel S Boss, Ryan Pavlick, Anthony Freeman, Cecile S Rousseaux, John Dunne, Matthew C Long, Eduardo Klein, Galen A McKinley, Joachim Goes, Ricardo Letelier, Maria Kavanaugh, Mitchell Roffer, Astrid Bracher, Kevin R Arrigo, Heidi Dierssen, Xiaodong Zhang, Frank W Davis, Ben Best, Robert Guralnick, John Moisan, Heidi M Sosik, Raphael Kudela, Colleen B Mouw, Andrew H Barnard, Sherry Palacios, Collin Roesler, Evangelia G Drakou, Ward Appeltans, Walter Jetz
The biodiversity and high productivity of coastal terrestrial and aquatic habitats are the foundation for important benefits to human societies around the world. These globally distributed habitats need frequent and broad systematic assessments, but field surveys only cover a small fraction of these areas. Satellite-based sensors can repeatedly record the visible and near-infrared reflectance spectra that contain the absorption, scattering, and fluorescence signatures of functional phytoplankton groups, colored dissolved matter, and particulate matter near the surface ocean, and of biologically structured habitats (floating and emergent vegetation, benthic habitats like coral, seagrass, and algae)...
March 6, 2018: Ecological Applications: a Publication of the Ecological Society of America
J Berger, J-R Bidlot, M A Dzieciuch, W E Farrell, P F Worcester, R A Stephen
The ocean acoustic noise floor (observed when the overhead wind is low, ships are distant, and marine life silent) has been measured on an array extending up 987 m from 5048 m depth in the eastern North Pacific, in what is one of only a few recent measurements of the vertical noise distribution near the seafloor in the deep ocean. The floor is roughly independent of depth for 1-6 Hz, and the slope (∼ f-7 ) is consistent with Longuet-Higgins radiation from oppositely-directed surface waves. Above 6 Hz, the acoustic floor increases with frequency due to distant shipping before falling as ∼ f-2 from 40 to 800 Hz...
February 2018: Journal of the Acoustical Society of America
Oleg A Godin, Alexander B Baynes
Anthropogenic noise pollution of the ocean is an acute and growing problem. This letter explores one possible mechanism of noise abatement. The far-field acoustic pressure due to a compact underwater source can be suppressed by placing a small compliant body in the vicinity of the source. Here, the feasibility and efficiency of the suppression are evaluated by quantifying the reduction in radiated acoustic energy for several simple geometries, which include sound sources in an unbounded fluid, near a reflecting boundary, or in a shallow-water waveguide...
February 2018: Journal of the Acoustical Society of America
Thomas J Deal
The cross-spectral density between pressure and particle velocity channels of two vector sensors with arbitrary orientation and separation is developed for a noise field consisting of directional sources distributed on a plane. Equations for arbitrary sensor orientations are necessary because cross-spectral density is an averaged product of two sensors' outputs that cannot be projected onto another direction after it is calculated. This prevents the use of existing methods, which calculate cross-spectral density for orthogonal particle velocity sensors, for sensors with different orientations...
February 2018: Journal of the Acoustical Society of America
Oleg A Godin
Interferometry of underwater noise provides a way to estimate physical parameters of the water column and the seafloor without employing any controlled sound sources. In applications of acoustic noise interferometry to coastal oceans, the propagation environment changes appreciably during the averaging times that are necessary for the Green's functions to emerge from noise cross-correlations. Here, a theory is developed to quantify the effects of nonstationarity of the propagation environment on two-point correlation functions of diffuse noise...
February 2018: Journal of the Acoustical Society of America
Martin Siderius, Jie Li, Peter Gerstoft
Seismic interferometry recovers the Green's function between two receivers by cross-correlating the field measured from sources that surround the receivers. In the seismic literature, it has been widely reported that this processing can produce artifacts in the Green's function estimate called "spurious multiples" or the "virtual refracted wave." The spurious multiples are attributed to the head wave and its multiples and travels in the seabed. The head wave phenomenon is shown to be observable from both controlled active sources and from ocean ambient noise and for both vertical and horizontal arrays...
February 2018: Journal of the Acoustical Society of America
Sam H Ridgway, Dianna S Dibble, Jaime A Kennemer
Two dolphins carrying cameras swam in the ocean as they searched for and marked mine simulators - buried, proud or moored. As the animals swam ahead of a boat they searched the ocean. Cameras on their harness recorded continuous sound and video. Once a target was detected, the dolphins received a marker to take to the simulator's location. During search and detection, dolphins made almost continuous trains of varying interval clicks. During the marking phase, shorter click trains were interrupted by periods of silence...
February 20, 2018: Biology Open
Danuta Maria Wisniewska, Mark Johnson, Jonas Teilmann, Ursula Siebert, Anders Galatius, Rune Dietz, Peter Teglberg Madsen
Shipping is the dominant marine anthropogenic noise source in the world's oceans, yet we know little about vessel encounter rates, exposure levels and behavioural reactions for cetaceans in the wild, many of which rely on sound for foraging, communication and social interactions. Here, we used animal-borne acoustic tags to measure vessel noise exposure and foraging efforts in seven harbour porpoises in highly trafficked coastal waters. Tagged porpoises encountered vessel noise 17-89% of the time and occasional high-noise levels coincided with vigorous fluking, bottom diving, interrupted foraging and even cessation of echolocation, leading to significantly fewer prey capture attempts at received levels greater than 96 dB re 1 µPa (16 kHz third-octave)...
February 14, 2018: Proceedings. Biological Sciences
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