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Comparison of Pressure and Intensity Methods in Evaluating the Directional Diffusion Coefficient

100%
Pilch A., Kamisiński T., Zastawnik M.
Acta Physica Polonica A
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2013
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vol. 123
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issue 6
1054-1058
EN
The directional diffusion coefficient characterizes directional uniformity of acoustic energy reflected from a structure. The goal of the paper is to check whether different measurement methods of that coefficient give comparable results and can be used for different diffusing structures. ISO 17497-2:2012 recommends two basic measurement methods for this parameter, both based on sound pressure analysis. In the first method, one microphone and a measurement manipulator is used (the space method), while in the second one, 19 microphones placed on the sound-reflecting plane are required (the boundary method). In the standard it is assumed (as usually in the room acoustics), that the acoustic energy is proportional to the square of sound pressure, what is true only for the plane wave. Correctness of this assumption was checked by the modified space method where the sound intensity probe was installed instead of microphone. The test revealed that pressure methods gave comparable results for both low- and high-diffusion structures, with the boundary method giving moderately higher values for low-diffusion structures and slightly higher for high-diffusion structures. The results obtained in the intensity method were comparable with the pressure method except for the 2000 Hz frequency range.
2
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The Application of Double-layer Curtains for Shaping Acoustics of Concert Halls

100%
Pilch A., Karlińska A., Snakowska A., Kamisiński T.
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vol. 125
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issue 4A
A-113-A-116
EN
Requirements concerning adjustment of acoustical parameters are nowadays more and more frequently numbered among design assumptions adopted for newly constructed concert halls and other auditoriums planned to play different functions. Investors usually require that the newly designed interiors can be used for such different purposes as playing orchestral music, performing theatre spectacles, screening movies, or holding lectures. This means the necessity to undertake studies on new technologies allowing to excert effective control over acoustics of multipurpose auditoriums. This paper proposes to use acoustic curtains as an effective means of modification of acoustic absorptivity of rooms. A design solutions for such curtains is described together with basics of the theory allowing to predict their acoustic properties. Results of sound absorption coefficient calculations performed for selected systems on the grounds of airflow resistivity values assumed for the used fabrics are verified by means of results of measurements performed in the impedance tube. It is proven that double-layer curtains show more balanced sound absorption characteristics compared to single-layer curtains and therefore represent a more convenient option when used for acoustical adaptation of rooms. Based on model studies, design solutions with double-layer curtains is developed for two concert halls that allow to adjust acoustic properties of the interiors to the required functions.
3
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The Study of Sound Scattering Structures for the Purposes οf Room Acoustic Enhancement

100%
Kamisiński T., Rubacha J., Pilch A.
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EN
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: Acoustics - Sound-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.
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