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The Uncertainty of Noise Composed of Separate Sound Events

100%

Makarewicz R. , Gołębiewski R.

Archives of Acoustics

2016

tom Vol. 41, No. 1

133--138

Transportation noise is a main source of noise pollution. It is assumed that it consists of recognizable noise events which come from moving aircrafts, trains and boats. The noise of an isolated sound event is assessed by the sound exposure level, LAE. Much legislation and many regulations and guidelines employ the A-weighted time-average sound level, LAeq,T, with the time interval T of one hour or longer. LAE measurements enable an approximation of LAeq,T. The key point is the uncertainty of this approximation. It has been shown that an increase in the number of LAE categories brings about a decrease in uncertainty. For illustrative purposes, LAE measurements of aircrafts taking off and landing were carried out.

Simple methods for determination of the acoustical properties of ground surfaces

63%

Gołębiewski R.

tom Vol. 32, No. 4

827--837

The interactions between the sound wave and the ground surface belong to the most important phenomena determining the outdoor noise propagation. In the present study, the exact theory of noise propagation and two simple models of the ground effect are analysed. The paper presents a method of determination of the effective flow resistivity, based on the twochannel measurement of the sound level (the exact theory). For the simplied model of the ground effect, the adjustable parameters are given as a function of the effective ow resistivity. Similarly for the ground effect model given by ISO 9613, the dependence of the ground factor (as a function of the effective flow resistivity) is presented. Additionally, for a few selected types of ground surfaces, the values of the model parameters were determined.

The Uncertainty of Noise Composed of Separate Sound Events

44%

Makarewicz R. , Gołębiewski R.

nr 1

Numerické modelování šířeni hluku

32%

Biskup M.

tom z. 19

13-16

This paper is concerned in modeling of noise propagation of a small end-fixed plate. The excitation was harmonic in range of audibility region. The modeling of noise propagation is made in MATLAB r.6. The noise propagation is calculated in ANSYS 5.7 because of comparing. The analysis of size of acoustic field in effect on a sound pressure level in case of model without boundary elements in the border of acoustic field is made.