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Design guidelines for interior acoustics in learning spaces included in European and American technical standards and other documents are presented. The current Polish regulations referring to interior acoustics are described. The proposal of a set of acoustical guidelines for improving acoustical comfort in school spaces is given.
Development of the index method for acoustic assessment of Roman Catholic churches is presented in the article. The current version of the global index was developed on the grounds of studies conducted in 8 churches and was based on 4 partial assessment indices: reverberation, music sound, speech intelligibility, and external disturbances. The use of sound strength as another partial index for global assessment is proposed in the article. A new formula of the global index for assessment of the acoustic quality of Roman Catholic churches is proposed. The computational procedure of the global index which uses analytical tools such as singular value decomposition (SVD) and comparative multivariate analysis (CMA) resulted from studies and analyses performed on an index observation matrix that was larger than before. Verification of index assessment was carried out for a sample of 12 Roman Catholic churches.
The analysis of uncertainty related to evaluation of sound insulation of partitions performed according to standard solutions recommended in The Guide to the Expression of Uncertainty in Measurement (GUM) by ISO/IEC-1998 and according to the new method based on the interval analysis - is presented in the paper. Both methods are compared and their application advantages presented. Limitations of the current solutions based on the law of propagation of uncertainty are shown. The method of the estimate derivation for the sound insulation based on interval arithmetic related to the measurement data is presented. The influence of the input parameters uncertainty on the calculation results of the sound insulation of partitions is determined. The considerations are illustrated by numerical examples.
Previous studies and analyses conducted up to now on the indicatory description of the acoustic quality of buildings concerned single value indices based on several selected acoustic parameters that are correlated with each other. Transformation of values, correlated into a new set of independent components for the purpose of their future synthesis, took place using the Singular Value Decomposition (SVD) technique. In this article, it is shown that SVD can also be applied to the determination of the single-value global acoustic quality index in the case where the decomposed index observation matrix contains partial indices that are not only correlated, but also uncorrelated. Alternatively, a statistical method used in econometrics, i.e. Comparative Multivariate Analysis (CMA), was adapted to obtain a single-value index from uncorrelated partial indices. Both proposed methods of synthesis have been verified using the example of a group of buildings - Roman Catholic churches.
Overhead stage canopies composed of many panels suspended under ceiling provide proper acoustic field in concert halls and auditoria. The purpose of using these structures is adequate direction and partial dispersion of sound reflected from them. Frequency range of sound reflected from flat panels closely depends on their shape, size and configuration. It is often too narrow and therefore insufficient for the proper sound of the interior. Mutual dependence of the lower and upper frequency limit of sound transmission requires the search for other ways to improve these structures. The paper proposes some solutions concerning spatial structures which have not been yet defined. An attempt was made to determine the useful frequency band of sound transmitted through such reflective structures.
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.
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.
The paper presents an original method for sound reinforcement in open areas. The method enabled both a regular sound reinforcement and the required spatial impressions of sound to be achieved in the area used for the study. The inverse image source method was used for the disposition of sound sources in order to find the inverse problem solution for determining the configuration of additional sound sources. Simulations demonstrated the improvement of sound impressions in the area in question and the simulations results were verified experimentally. The intended result of the proposed method was the increase of the lateral energy fraction and lateral energy fraction coefficient parameter values by 6 and 8 points, respectively, for the simulation by 5 and 7 points for the experiment. It should be stated that, in both the simulation and the experiment, eligible values for the acoustic parameters were obtained after using the sound system with additional sound sources, the speech intelligibility value parameters remain at an excellent level. In conclusion, it may be claimed that the proposed sound reinforcement system makes the creation of the intended spatial sound impressions in an open area possible.
Results of computer simulations and measurements in real interior for varying location of sound source and microphone are shown in the paper. A small room with a volume of 47 m^3 was used for this purpose. The objective of measurements and calculations was to determine the sound pressure level and other parameters derived from the room impulse response (T_{30}, EDT, C_{80}, STI) followed by the sensitivity analysis of those parameters to changing the location and orientation of the sound source and the receiver. In order to determine these parameters, the room impulse response was measured using MLS method. Experimental studies have been used to verify the acoustic room model built with use of enhanced radial method algorithms and its sensitivity. That allowed complementary and extended simulation studies on the room acoustic characteristics and finally determination of sensitivity of output parameters to changes of location and orientation of the measurement channel elements.
Providing appropriate sound field parameters in the listening area is very important. It often determines the possibilities of being able to use a facility. Assuming that the sound system is a linear object, it can be described by the impulse response. Unfortunately, it is not possible to designate a single impulse response for such a facility because it is a continuous system. Thus each path between the transmitter and the receiver has its own impulse response. Therefore, the authors have made an attempt to synthesize the impulse response for transmitter-receiver paths with suitable parameters of the sound field in the neighbourhood of the receivers. A technical implementation of the presented synthesis will take place through introduction of additional sources. An experimental determination of the impulse response is relatively simple. The transient response can be numerically determined by using, for example, the finite element method or the boundary element method. Unfortunately, determining the impulse response through simulation of, e.g., planned objects, is much more difficult due to the high computational cost and the lack of precise data on the properties of the materials. For this reason, the authors used an energetic analogue of the impulse response, the echogram.
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