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Mourão Bento, H.F. (author), VanDercreek, Colin (author), Avallone, F. (author), Ragni, D. (author), Sijtsma, P. (author), Snellen, M. (author)Aeroacoustic tests in closed wind tunnels are affected by reflections in the tunnel circuit and background noise. Reflections can be mitigated by lining the tunnel circuit. The present study investigates if lining exclusively the most accessible segment of a closed wind tunnel circuit, in particular the test section, is an approach which...conference paper 2023
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Van der Grift, R.C. (author), Snellen, M. (author), Simons, D.G. (author)Accurate modelling of aircraft noise in different weather conditions is crucial for the reliability of noise predictions and their application worldwide. In best-practice aircraft noise models, such as Doc.29, the change in expected sound level on the ground due to changing atmosphere is modelled with a simplified propagation calculation. The...conference paper 2023
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Sijtsma, P. (author), Brouwer, Harry (author), Snellen, M. (author)The fan-stator stage of turbofan engines is one of the main regions of broadband noise generation. The trend of increasing bypass ratios will make fan-stator broadband noise even more significant, as jet noise will decrease and nacelles will become shorter, thus leaving less space for liners. Within the fan-stator stage there are several...conference paper 2023
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Altena, A. (author), Luesutthiviboon, S. (author), de Croon, G.C.H.E. (author), Snellen, M. (author), Voskuijl, M. (author)Due to technological advances in the drone industry, security threats induced by unmanned aerial vehicles (UAVs) are becoming more relevant. Fast and accurate localisation systems need to be designed. One approach is localisation of UAVs by their sound using acoustic techniques. So far, a systematic performance assessment of acoustic...conference paper 2023
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Bai, Q. (author), Mestdagh, S.M.F. (author), Snellen, M. (author), Amiri Simkooei, A. (author)Acoustic classification using single-beam and multi-beam echosounders has been widely applied in characterizing seabed sediments. Although previous studies have shown a better discrimination of fine and coarse sediments using multi-spectral echosounder data, analysis regarding comprehensive seabed sediment properties is still needed. In this...conference paper 2023
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Mestdagh, S.M.F. (author), Bai, Q. (author), Snellen, M. (author)Detailed knowledge of both the sedimentological and ecological characteristics of the seafloor is essential when undertaking bottom-disturbing activities, but can be a challenge to obtain. Through backscatter data at different frequencies, collected with a multi-spectral multi-beam sonar, information on the structure of both the sediment...conference paper 2023
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Domingos de Azevedo Quadros, F. (author), Snellen, M. (author), Dedoussi, I.C. (author)Aircraft emitted oxides of nitrogen (NOx) contribute both to climate change and air quality degradation. The trend of higher gas temperatures, caused by engine design choices seeking lower fuel consumption and achieve more complete combustion, has the adverse effect of increasing NOx formation, which might however be compensated by improved...conference paper 2022
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Merino Martinez, R. (author), VanDercreek, Colin (author), Snellen, M. (author)Aeroacoustic measurements with microphones in closed-section wind tunnels are typically hampered by the pressure fluctuations of the turbulent boundary layer (TBL) on the tunnel's walls, ceiling, or floor, where phased microphone arrays are usually mounted. This paper evaluates the performance of several advanced acoustic imaging methods that...conference paper 2022
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Merino Martinez, R. (author), von den Hoff, B. (author), Morata, David (author), Snellen, M. (author)Complex test models in aeroacoustic experiments often present an arrangement of noise sources within a three–dimensional space. Planar microphone array normally have difficulties in separating sound sources in the direction normal to the array plane due to their poorer spatial resolution in this direction. This paper evaluates the benefits of...conference paper 2022
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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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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
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Merino Martinez, R. (author), Herold, Gert (author), Snellen, M. (author), Dougherty, Robert P. (author)Functional Projection Beamforming (FPB) is a method proposed by Dougherty in 2019, based on functional beamforming. It yields the integrated sound spectrum for a given region of integration (ROI) within the functional beamforming source map. FPB does not suffer from the loss of level that can affect functional beamforming, especially for coarse...conference paper 2020
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Merino Martinez, R. (author), Snellen, M. (author)Landing gear noise is considered the dominant airframe noise source on aircraft during approach. Previous studies indicated the presence of a strong tonal sound on flyovers of several commercial aircraft types, and suggested that it was caused by the interaction of open cavities in the nose landing gear (NLG) system with the flow. Airframe...conference paper 2020
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Amiri Simkooei, A. (author), Koop, L. (author), Snellen, M. (author), Simons, D.G. (author)In the last two decades, the use of multibeam echosounders has been growing for seafloor mapping and characterization. The former uses bathymetry data whereas the latter makes use of backscatter data. The use of backscatter data has been the subject of intensive research to gain insight into seafloor composition using either empirical or model...conference paper 2019
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Wijnker, Dirk (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 (UAV) can detect manned aircraft with a single microphone, an audio data set is created in which UAV ego-sound and recorded aircraft sound are mixed together. A convolutional neural network is used to perform the air traffic detection. Due to restrictions on flying UAVs close to aircraft, the data set...conference paper 2019
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Mohammadloo, Tannaz H. (author), Snellen, M. (author), Amiri Simkooei, A. (author), Simons, D.G. (author)Nowadays Multi-Beam Echo-Sounder (MBES) systems are used for obtaining information of the sea/river bed bathymetry and sediment composition. For the latter, use is usually made of the backscatter strength and depth derivatives, such as depth residuals. However, the depth derivatives are affected by the uncertainties inherent to the MBES varying...conference paper 2019
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Merino Martinez, R. (author), Pieren, R.D. (author), Snellen, M. (author), Simons, D.G. (author)Noise emissions from wind turbines are one of the main issues that the wind energy industry must deal with nowadays. Strict noise regulations often prevent wind turbines to operate at maximum power conditions, causing large losses of power production and, hence, of revenue. Several noise reduction measures have been proposed so far, but the...conference paper 2019
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Mohammadloo, Tannaz H. (author), Snellen, M. (author), Amiri Simkooei, A. (author), Simons, D.G. (author)Nowadays Multi-Beam Echo-Sounder (MBES) derived bathymetry is used for a large range of applications. However, these measurements are affected by the uncertainties inherent to the MBES. Since the development of the depth uncertainty prediction model, MBES systems have been improved noticeably. The present contribution addresses the importance of...conference paper 2019
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VanDercreek, Colin (author), Manjunath, P. (author), Ragni, D. (author), Snellen, M. (author)This study investigated how embedding microphones in different cavity geometries reduce the measured turbulent boundary layer pressure fluctuations at the microphones. The cavity geometries were systematically varied using a design of experiments (DOE) methodology. This approach tested different cavity depths, diameters, chamfers, and opening...conference paper 2019
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Merino Martinez, R. (author), Vieira, A.E. (author), Snellen, M. (author), Simons, D.G. (author)Aircraft noise is an increasingly important issue that causes annoyance and complaints for the communities living in the vicinity of airports. The conventional sound metrics (such as the A–weighted sound pressure level) typically used for assessing the impact of aircraft noise often fail to conveniently represent the actual annoyance...conference paper 2019