The objective of this study was to determine normal impedance on the surface as well as sound absorption coefficients for several wood species from Europe and from the tropical zone. The mathematical models of Miki, Attenborough, and Allard – dealing with acoustic properties of porous materials – have also been compared. The air flow resistivity exhibits a distinct link between fiber dimensions and wood porosity. The highest sound absorption coefficient was found for oak, ash, sapeli, and pine woods at 2 kHz frequency. The Attenborough model provides results closest to laboratory measurements, although it still requires significant improvements. The Miki and Allard models have some drawbacks and should be applied with reservation for the determination of wood acoustic properties.
From modern buildings to public spaces are made of concrete, steel, and glass. These materials increase propagation of sound and the reverberation time. Therefore, furniture should be good sound absorbers in such places. The objective of this study was to ascertain acoustic properties of wood-based materials by determining normal acoustic impedance on the surface and sound absorption coefficients. Experiments were carried out on 17 types of wood-based materials commonly employed in furniture design and manufacture. Investigations were conducted based on the transferfunction method. It was demonstrated that for frequencies between 125 and 500 Hz, the highest capability of sound absorption was determined of low surface layer density and high porosity. Honeycomb panels with paper core absorbed better sounds in the range between 1 and 2 kHz. Panels of considerable external surface irregularities were characterized by the most favorable acoustic properties for the frequency of 4 kHz.
Acoustic structures are currently classified mainly in terms of their acoustic absorption and insulation properties. Knowing the sound scattering parameter can significantly improve the useful value of materials and identify their best applications. Currently no studies are performed in Poland on the sound scattering coefficients of materials. This is due to a complex measurement procedure and a lack of legal requirements. The authors have attempted to make such measurements on the basis of the standard ISO 17497-1:2004: AcousticsSound-scattering properties of surfaces -Part 1: Measurement of the random-incidence scattering coefficient in a reverberation room. Measurement and calculation methods are presented, and problems encountered during this study have been described. This issue is of particular importance, especially in the acoustic design of interiors.
ATHENA is the L2 mission selected by ESA to pursue the science theme "Hot and Energetic Universe" (launch scheduled in 2028). One of the key instruments of ATHENA is the Wide Field Imager (WFI) which will provide imaging in the 0.1-15 keV band over a 40'x40' large field of view, together with spectrally and time-resolved photon counting. The WFI camera, based on arrays of DEPFET active pixel sensors, is also sensitive to UV/Vis photons. Optically generated electron-hole pairs may degrade the spectral resolution as well as change the energy scale by introducing a signal offset. For this reason, the use of an X-ray transparent optical blocking filter is needed to allow the observation of all type of X-ray sources that present a UV/Visible bright counterpart.In this paper, we describe the main activities that we are carrying on for the conceptual design of the optical blocking filter, that will be mounted on the filter wheel, in order to satisfy the scientific requirements on optical load from bright UV/Vis astrophysical source, to maximize the X-ray transmission, and to withstand the severe acoustic and vibration loads foreseen during launch.
Paper presents a numerical simulation of the acoustics of selected concert halls performed using CATT--acoustic software, and the results of acoustic measurements performed in these spaces.
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