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.
This paper presents a mechanical positioning system for a measuring microphone designed for acoustic studies in anechoic and reverberation chambers at the Department of Mechanics and Vibroacoustics, AGH. The results are discussed in the context of mechanical positioning and its impact on the outcome of the execution of individual measurement procedures. Moreover, areas for research were identified and solution concepts shown for further development of the automation of acoustic measurements in different research rooms in order to reduce the human involvement in them.
The present work analyses the absorption coefficient of sound waves and the speed of sound propagation in thermally modified wood. The high resistance to weathering, fungi, and better dimensional stability, and therefore the broad physical properties of this material, are well known. However, the literature lacks numerous analyses of its acoustic characteristics. During the study, high-density species, such as oak, red oak, and beech were used, in contrast to pine. Pine wood during this test was characterised by a most rapid increase in the sound absorption coefficient value, in the range of 1000–6300 Hz, and reached the highest value from all wood species. Among all species, the highest value of the examined parameter was obtained for beech wood and pine wood, which were 0.213 (at frequency 3 kHz) and 0.183 (at 6.3 kHz), respectively. The sound velocity decreased for all species only in the tangential direction.
The paper presents the new solution to a road acoustic screen consisting of elements which are highly diffusing and simultaneously resistant to weathering, but also characterised by a sound absorption. There is described the comprehensive research of such the road acoustic screen with absorbing and diffusing surface. The study includes screen's resistance to wind load and snow removal, impact tests and measurements of some acoustic parameters.
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