Hydroacoustics (United States)

Previous UAM noise studies showed already that most of the aircraft noise will occur close to the vertiports and therefore is requiring a careful selection of observer positions for community noise studies and noise impact testing, depending mainly on the aircrafts' changing operational conditions during take-off and approach. While vertiports can be situated close to the next residential areas of a community, the noise, generated during take-off and landing is playing an important role. Especially before and short after take-off, as well as short before or after landing, most air-taxis' operational parameters, such as rotor rpm, velocity and in some cases tilt-angle of wing/engines, can vary significantly in a very short time, sometimes only within seconds. This so-called transition phase is of high importance to describe the aircraft's acoustics during its specific flight phases before reaching the final flight conditions for cruise, or the landing process is completed. The work presented here was performed in the frame of the research project PAULA and is showing for the first time, how different sections of the air-taxis' trajectory are differently contributing to community noise during take-off and approach.

El monitoreo de los cuerpos de agua superficiales como lagos, lagunas, embalses y ríos es esencial para la gestión sustentable del agua, especialmente cuando estos cuerpos atraviesan períodos de excesos y de déficits hídricos por lo que es habitual colocar estaciones limnimétricas automáticas para registrar su nivel. Para el caso específico de los embalses, se necesita esta información para el manejo del agua de la presa y para poder proyectar el volumen útil en el futuro. Sin embargo, existen cuerpos de agua que no cuentan con este tipo de registros por lo que es necesario evaluar metodologías alternativas para monitorearlos. En este trabajo se avanza en la validación preliminar de productos de la misión satelital SWOT (del inglés, Surface Water and Ocean Topography), lanzada en diciembre de 2022, para determinar los niveles de estos cuerpos de agua cruciales para provisión de agua, mantenimiento de la biodiversidad, etc. En primera instancia la evaluación se focaliza en el embalse del Dique San Roque, Córdoba. En ese cuerpo de agua se obtiene una mejora en la estimación del nivel de la superficie de agua utilizando el subproducto PIXC al comparar con observaciones en el terreno (raíz del error

Abstract This study expands previous work examining the effects on fishes from exposure to a single 4.5 kg underwater explosive detonation. Experiments were done in the field, with fish in cages at different distances from the source. Although our earlier work reported high acoustic dosage levels (e.g. based on peak pressure) correlating with severe injuries, dosage levels that result in moderate, or mild injuries were not clearly established. Thus, in this study, caged Pacific mackerel (Scomber japonicus) were placed at targeted ranges of 150–800 m from the source. All procedures were the same as in the earlier study except that animals were left at depth for ∼3 hours post-exposure to determine immediate effects on survival. Fish were then retrieved and assessed for physical damage. The only statistically significant tissue injuries were swim bladder bruising and in a reduction in inner ear sensory hair cell density that lessened with distance from the source. Still, results must be taken with caution since they may vary with different source levels, water depths, location of the fish in the water column, and by species.

Aquatic animals (invertebrates, fishes, and marine mammals) are encountering an increasing array of underwater anthropogenic noises that can disrupt and even harm ecosystems as well as the lives of individuals and populations. Sources of anthropogenic noise include, but are not limited to, shipping, offshore exploration and production for fossil fuels, and the construction and operation of wind farms. Because of the continuing increase in anthropogenic noise, research on its potential effects on aquatic animals has intensified over the past two decades. However, a major under-explored issue is that noise is only one type of anthropogenic pressure acting (often simultaneously) on animals. Indeed, multiple simultaneous anthropogenic pressures are likely to affect how aquatic animals respond to each of the individual stimuli. Moreover, animal responses may be very different in the presence of multiple pressures as compared to when there is only a single anthropogenic source. We suggest refocusing of aquatic noise so that research prioritizes studies that deal with the interaction of noise with other anthropogenic pressures on aquatic life. At the same time, we call for an acceleration of studies providing baseline data for cumulative risk studies, such as monitoring of ambient noise around the globe.

View Video Presentation: https://doi.org/10.2514/6.2023-3839.vid The deconvolution method CLEAN-SC is proposed as a tool for analysing engine static tests with far-field microphone arrays. Using measurements on a DGEN380 engine, it was demonstrated that CLEAN-SC is able to make a breakdown of the different engine noise sources (jet, core, bypass, intake) and to determine the far-field directivity of each source. Even the challenging task of separating core noise from jet noise was performed successfully, including the directivity.

Abstract A multimethod geoelectric survey was implemented between January and March 2022 along a 220‐m long reach of the bedrock‐lined streambed of East Fork Poplar Creek in Oak Ridge, Tennessee to identify locations of surface‐water and groundwater exchange and characterize the subsurface flow paths that convey water between the stream and flood plain. A waterborne self‐potential (WaSP) survey was completed in January 2022 to measure the electric streaming‐potential field in the stream. Electric resistivity tomography (ERT) was performed in March 2022 on the flood plain adjacent to the WaSP survey reach to map the electric resistivity distribution and characterize the hydrogeology and subsurface flow paths that facilitate surface‐water and groundwater exchange in the bedrock‐lined stream. The combination of WaSP and ERT data support the qualitative interpretation that surface‐water and groundwater exchange likely occurs along fractures in outcropping bedrock and along two fault lines that intersect the limestone creek bed.

Bowhead whales generally migrate into high Arctic waters in the summer months and move to lower latitudes in the wintertime. During the 1800s and early 1900s commercial whaling greatly reduced the numbers of bowhead whales in waters adjacent to the North Atlantic Ocean. In recent decades their numbers have been increasing. Thirteen sightings of a bowhead whale were recorded in four areas of the Gulf of Maine in 2012, 2014, and 2017 between latitudes 44°43’N and 41°36’N, far south of the normal range (54°N) for this species. Photographs obtained during these sightings were compared by experienced photo analysts and, based on scarring patterns, the sightings were confirmed to be of the same individual. The bowhead whale was observed alone, in addition to interacting in a social group and engaged in coordinated feeding with other mysticetes at times. The feeding and social behaviour of the bowhead whale was typical for the species but well south of its normal Arctic waters range and in the absence of conspecifics.

Reconstitution of normal skin anatomy after full thickness skin loss may be accomplished using a combination of a dermal regeneration template (DRT) and a split thickness skin graft (STSG). However, because of the relatively low rate of cell infiltration and vascularization of currently available DRTs, reconstruction is almost always performed in a two-step procedure over the course of several weeks, resulting in multiple dressing changes, prolonged immobilization, and increased chance of infection. To mitigate the potential complications of this prolonged process, the collagen-based dermal template DermiSphere™ was developed and tested in a single-step procedure wherein DermiSphere and STSG were implanted simultaneously. When evaluated in a porcine, full thickness, excisional wound model, DermiSphere successfully supported simultaneous split thickness skin graft take and induced functional neodermal tissue deposition. When compared to a market leading product Integra Bilayer Wound Matrix, which was used in a multistep procedure (STSG placed 14 days after product implantation according to the product IFU), DermiSphere induced a similar moderate and transient inflammatory response that produced similar neodermal tissue maturity, thickness, and vascularity, despite being implanted in a single surgical procedure leading to wound closure 2 weeks earlier. These data suggest that DermiSphere may be implanted in a single-step procedure with an STSG, which would significantly shorten the time course required for the reconstruction of both dermal and epidermal components of skin after full thickness loss.

In order to achieve the attenuation of low‐frequency sound, in this paper, a hybrid metamaterial structure with a complete band gap below 500 Hz is proposed, which is subjected to second‐order fractal, series fusion, and whether the structure is framed or not to form 8 different structures. Based on the finite element method and Bloch's theorem, the bandgap and transport properties of all model structures are evaluated, and the bandgap and propagation properties of metamaterial structures with different fractal levels are elucidated in terms of band structure and group velocity. In addition, the third‐order fractal structure and the dependence of the band gap on the material are also studied. The results show that the structure has a superior band gap width, and the complete band gap of its tandem fusion structure accounts for up to 45.502% in the range of 500 Hz, and the second‐order fractal has a complete band gap of 45.588% in the range of 1000 Hz. Compared with other structures, it can produce lower and better band gap. The research in this paper provides a new strategy for realizing acoustic metamaterial structures with low frequency band gaps.