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Uncertainty Evaluation in Modelling of Acoustic Phenomena with Uncertain Parameters Using Interval Arithmetic

100%
Batko W., Pawlik P.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1A
A-152-A-155
EN
Uncertainty assessment in modelling of acoustic phenomena with uncertain parameters using interval arithmetic on the example of the reverberation time estimation, are presented in the paper. The application of the classical interval analysis formalism as well as its expansions are shown. Statistical methods of estimation of the reverberation time are based on parameters, which are related, among others, to the geometry of the analysed room, characteristics of sound absorption, and interior transmission. Values of these parameters are usually difficult to determine, which has a significant influence on the modelling result. The interval analysis allows to determine the variability interval of the parameter being estimated. The authors determined the influence of the input parameters uncertainty on the estimated reverberation time, calculated according to the Sabine, Eyring-Norris and Millington-Sette formulae. The uncertainty analysis was performed for the literature data, related to the reverberation time calculations of the room of a certified acoustics.
2
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Uncertainty Assessment of Index M

80%
Batko W., Przysucha B.
Acta Physica Polonica A
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2012
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vol. 121
|
issue 1A
A-156-A-159
EN
Administrative decisions, related to the selection of the priority of activities minimising acoustic effects in the analysed areas, are determined by the index M values. This index is also known as the noise protection agents demand. A form of its function is determined by variables describing the number of residents and the level of exceeding the permissible noise in these inhabited regions. Uncertainty of decisions resulting from such assessments is conditioned by numerical measures: inaccurate measurements of exceeding permissible noise indicators as well as errors in the estimation of the number of residents exposed to them, formulated in probabilistic categories and interpreted in an interval way. Thus, the uncertainty assessment of index M, being the function determined by means of those variables, requires the determination of the density of probability distribution function of its occurrence. The method of its determination constitutes the contents of the presented hereby paper. The study concentrates on the derivation of the density of probability distribution function of index M, at the assumption that the distribution of variable errors is in a form of the normal cut distribution. The computational algorithm, allowing to perform necessary numerical calculations assigned to the uncertainty assessment process of index M, is presented. The obtained results are illustrated by the example.
3
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Random Distribution of Long-Term Indicators of Variable Emission Conditions

80%
Batko W., Przysucha B.
Acta Physica Polonica A
|
2011
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vol. 119
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issue 6A
1086-1090
EN
This study is dedicated to the problem of estimating uncertainties of long-term noise indicators, when differences in the sound level emission at various time periods of the calendar year are taken into consideration. This task is defined by referring their influence values - in the determined time intervals - to the year period. Due to the limited possibilities of a total monitoring of parameters necessary for the precise estimation of the long-term sound levels, this estimation process is often limited (in accordance with the EU environmental recommendations) to two condition classes. They are defined by two sound levels occurring with probabilities (frequencies) p and 1-p, in the analyzed reference period. In this paper we present a method of calculating uncertainties of this procedure assuming that frequency of determined events are known. The probability distribution for the estimated value was assessed. The developed model formalism of the estimation of uncertainties of long-term sound levels together with algorithms assigned to it, was analyzed. The proposed solution was illustrated by examples of uncertainty calculations of the averaged sound levels in acoustic assessments of environmental hazards.
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