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von den Hoff, B. (author), Simons, D.G. (author), Snellen, M. (author)Full-scale propeller measurements are useful to study the total noise contribution of a propeller-driven aircraft, including installation effects. Full-scale measurements under operational conditions also provide an accurate validation opportunity for propeller noise prediction models. These studies are, therefore, necessary to quantify and...conference paper 2022
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Simons, D.G. (author), Besnea, I. (author), Mohammadloo, Tannaz H. (author), Melkert, J.A. (author), Snellen, M. (author)The impressive growth of the aviation industry and the number of flights entail several environmental repercussions, such as increased aircraft noise emissions. With the worrying number of complaints from the communities around airports comes also the distrust in numerical models used for aircraft noise prediction. In this study, we compare...journal article 2022
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Mourão Bento, H.F. (author), VanDercreek, Colin (author), Avallone, F. (author), Ragni, D. (author), Snellen, M. (author)Microphone measurements in a closed test section wind tunnel are affected by turbulent boundary layer (TBL) pressure fluctuations. These fluctuations are mitigated by placing the microphones at the bottom of cavities, usually covered with a thin, acoustically transparent material. Prior experiments showed that the cavity geometry affects the...journal article 2022
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VanDercreek, Colin (author), Avallone, F. (author), Ragni, D. (author), Snellen, M. (author)Cavities placed along wind tunnel walls can attenuate the turbulent boundary layer (TBL) fluctuations as they propagate into the cavity. Placing microphones within the cavities can thus improve the signal-to-noise ratio of acoustic data. However, standing waves form within these cavities distorting the acoustic measurements. This work uses a...journal article 2022
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von den Hoff, B. (author), Merino Martinez, R. (author), Simons, D.G. (author), Snellen, M. (author)Complex acoustic systems typically present three-dimensional distributions of noise sources. Conventional acoustic imaging methods with planar microphone arrays are unsuitable for three-dimensional acoustic imaging, given the computational demands and the incapability to explicitly account for the presence of multiple sources. This paper...journal article 2022
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Domingos de Azevedo Quadros, F. (author), Snellen, M. (author), Sun, Junzi (author), Dedoussi, I.C. (author)Aviation is a growing source of atmospheric emissions impacting the Earth’s climate and air quality. Comprehensive assessments of the environmental impact of this industry require up-to-date, spatially resolved, and speciated emissions inventories. We develop and evaluate the first such estimate of global emissions from aircraft operations for...journal article 2022
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Mourão Bento, H.F. (author), Ragni, D. (author), Avallone, F. (author), Simons, D.G. (author), Snellen, M. (author)Sound absorbing porous materials are used to line a wind tunnel wall, in order to reduce reflections. However, the lining can have a detrimental effect on the acoustic measurements due to an increase in the noise radiated from the walls. In addition, the aerodynamic fidelity of the tunnel can be affected. In the present study, the influence...journal article 2022
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Keyzer, L.M. (author), Mohammadloo, Tannaz H. (author), Snellen, M. (author), Pietrzak, J.D. (author), Katsman, C.A. (author), Afrasteh, Y. (author), Guarneri, H. (author), Verlaan, M. (author), Klees, R. (author), Slobbe, D.C. (author)The sound speed provides insight in ocean properties, as it depends on depth, temperature and salinity. Here, we propose a method to invert sound speed profiles (SSPs) from multibeam echosounder (MBES) measurements, providing a SSP for every ping. Using erroneous SSPs results in a mismatch in the estimated bathymetry between overlapping swaths....book chapter 2021
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Luesutthiviboon, S. (author), Ragni, D. (author), Avallone, F. (author), Snellen, M. (author)This study focuses upon a new permeable topology design concept as an alternative to porous metal foams, for turbulent boundary layer trailing-edge (TBL-TE) noise attenuation. The present permeable topology has unconventional characteristics with respect to the metal foams: a combination of low flow resistivity r and high form drag...journal article 2021
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Wijnker, D.C. (author), van Dijk, Tom (author), Snellen, M. (author), de Croon, G.C.H.E. (author), de Wagter, C. (author)To investigate how an unmanned air vehicle can detect manned aircraft with a single microphone, an audio data set is created in which unmanned air vehicle ego-sound and recorded aircraft sound are mixed together. A convolutional neural network is used to perform air traffic detection. Due to restrictions on flying unmanned air vehicles close to...journal article 2021
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Lima Pereira, L.T. (author), Merino Martinez, R. (author), Ragni, D. (author), Gómez-Ariza, David (author), Snellen, M. (author)This paper explores the advantages of combining asynchronous microphone array measurements for acoustic source mapping in two and three–dimensional applications. Four different approaches are considered, three consisting of the combination of the source maps (arithmetic mean, geometric mean, and minimum value), and a fourth one obtained by...journal article 2021
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Afrasteh, Y. (author), Slobbe, D.C. (author), Verlaan, M. (author), Sacher, M. (author), Klees, R. (author), Guarneri, H. (author), Keyzer, L.M. (author), Pietrzak, J.D. (author), Snellen, M. (author), Zijl, F. (author)The first objective of this paper is to assess by means of geodetic network analyses the impact of adding model-based hydrodynamic leveling data to the Unified European Leveling Network (UELN) data on the precision and reliability of the European Vertical Reference Frame (EVRF). In doing so, we used variance information from the latest UELN...journal article 2021
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van der Reijden, Karin J. (author), Govers, Laura L. (author), Koop, L. (author), Damveld, Johan H. (author), Herman, Peter M.J. (author), Mestdagh, S.M.F. (author), Piet, Gerjan (author), Rijnsdorp, Adriaan D. (author), Dinesen, Grete E. (author), Snellen, M. (author), Olff, Han (author)Conflicts of interests between economic and nature conservation stakeholders are increasingly common in coastal seas, inducing a growing need for evidence-based marine spatial planning. This requires accurate, high-resolution habitat maps showing the spatial distribution of benthic assemblages and enabling intersections of habitats and...journal article 2021
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Conservation Implications of Sabellaria spinulosa Reef Patches in a Dynamic Sandy-Bottom Environmentvan der Reijden, Karin J. (author), Koop, L. (author), Mestdagh, S.M.F. (author), Snellen, M. (author), Herman, P.M.J. (author), Olff, Han (author), Govers, Laura L. (author)Biogenic reefs form biodiversity hotspots and are key components of marine ecosystems, making them priority habitats for nature conservation. However, the conservation status of biogenic reefs generally depends on their size and stability. Dynamic, patchy reefs may therefore be excluded from protection. Here, we studied epibenthos and...journal article 2021
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VanDercreek, Colin (author), Merino Martinez, R. (author), Sijtsma, P. (author), Snellen, M. (author)Aeroacoustic measurements performed by flush-mounted microphone arrays on the walls of closed-section wind tunnels are contaminated by the hydrodynamic pressure fluctuations of the wall's boundary layer. This study evaluates three different microphone cavity geometries for mitigating this issue. Their improvement to the signal-to-noise ratio ...journal article 2021
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Koop, L. (author), Snellen, M. (author), Simons, D.G. (author)In this paper, object-based image analysis classification methods are developed that do not rely on backscatter in order to classify the seafloor. Instead, these methods make use of bathymetry, bathymetric derivatives, and grab samples for classification. The classification is performed on image object statistics. One of the methods utilizes...journal article 2021
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Rubio Carpio, A. (author), Avallone, F. (author), Ragni, D. (author), Snellen, M. (author), van der Zwaag, S. (author)An experimental study on broadband noise scattered by permeable trailing edges with different pore arrangements is performed. A NACA 0018 airfoil with chord c = 0.2 m is investigated at chord-based Reynolds numbers ranging from 1.4 × 10<sup>5</sup> to 3.8 × 10<sup>5</sup> and angles of attack of 0.2 and 5.4 degrees. Noise emission from five...journal article 2020
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Mestdagh, S.M.F. (author), Amiri Simkooei, A. (author), van der Reijden, Karin J. (author), Koop, L. (author), O'Flynn, Sarah (author), Snellen, M. (author), Van Sluis, Christiaan (author), Govers, Laura L. (author), Simons, D.G. (author), Herman, P.M.J. (author), Olff, Han (author), Ysebaert, Tom (author)High-resolution surveying techniques of subtidal soft-bottom seafloor habitats show higher small-scale variation in topography and sediment type than previously thought, but the ecological relevance of this variation remains unclear. In addition, high-resolution surveys of benthic fauna show a large spatial variability in community...journal article 2020
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Merino Martinez, R. (author), Luesutthiviboon, S. (author), Zamponi, R. (author), Rubio Carpio, A. (author), Ragni, D. (author), Sijtsma, P. (author), Snellen, M. (author), Schram, Christophe (author)In this paper, the performance of four acoustic imaging methods: conventional frequency domain beamforming (CFDBF), functional beamforming (FUNBF), enhanced high resolution CLEAN–SC (EHR–CLEAN–SC) and generalized inverse beamforming (GIBF), is investigated in terms of accuracy and variability. Three experimental test cases are considered: 1)...journal article 2020
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VanDercreek, Colin (author), Merino Martinez, R. (author), Snellen, M. (author), Ragni, D. (author), Simons, D.G. (author)This paper analyses the influence of microphone cavity geometry on beamforming measurements with a turbulent boundary layer present on the microphone array. A 16- microphone array was tested in the anechoic open-jet wind tunnel of the Delft University of Technology. The array was placed on a flat plate mounted flush with the exit nozzle of the...conference paper 2020