A number of objective ana subjective acoustical parameters, referring to the reverberance, and spatial distribution of sound and speech intelligibility, were measured before and after the acoustical adaptation of a classroom. Three configurations of arrangements differing in used materials' sound absorbing coefficient were analyzed. The results indicate the expected improvement of the acoustical environment according to design assumptions.
The problem of identification and localization of sound sources inside industrial rooms, including cases when the density of sound sources is considerable, can be solved by application of inverse methods. The experimental knowledge about the distribution of acoustic field in the neighborhood of the examined object, followed by the reversal of the model used for sound generation and propagation, leads to evaluation of the object's acoustic power. For the cases when determination of the rooms' acoustical properties is required the combination of the inverse method with the boundary elements method allows the calculation of acoustic impedance for the surface delimiting the examined room. The paper presents the prospects of the inverse method application in the mentioned vibroacoustic problems.
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.
Acoustic field in enclosed rooms in the low frequency range can be described by the wave model, based on solution of the wave equation. Solution to the wave equation for acoustic field in the room can be obtained using numerical procedures, e.g. the boundary elements method. Determination of acoustic impedance of the room walls surface material, based on the knowledge of the distribution of acoustic pressure amplitudes in the enclosed space, requires application of the inverse boundary elements method and gathering a proper set of input data. The paper presents the possibilities of analysis of acoustic properties for industrial-type rooms, by using inverse methods in the low frequency range.
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