HEAVY MACHINERY - HM 2011, 39-44 Paper accepted: 20.05.2011 ISBN 978-86-82631-58-3 * Corr. Author's Address: Faculty of Occupational Safety of Niš, Čarnojevića 10a, 18000 Niš, Serbia, dragan.cvetkovic@znrfak.ni.ac.rs Estimation of uncertainty in environmental noise measurement Dragan Cvetković 1,* - Momir Praščević 1 - Darko Mihajlov 1 1 University of Niš, Faculty of Occupational Safety of Niš It is well known that environmental noise levels can vary over a wide range as a result of the diversity of site conditions and activities occurring during field measurements. Environmental noise very often occurs in the form of randomly fluctuating sound signals. To quantitatively describe this phenomenon, noise index such as equivalent pressure level Leq is widely used. The measured value of Leq based on the sound pressure level measurements by sound level meter will probably differ from the true one due to the effects of the errors throughout the experiment chain and in the physical phenomenon under study. SRPS EN ISO 1996-2 (2010) contains guidelines on assessing the uncertainties of the determined sound pressure levels. This depends on the sound source, measurement time interval, weather conditions, distance from the source, measurement method and instrumentation. Guidelines on estimating the measurement uncertainty in compliance with the ISO Guide to Uncertainty in Measurements (GUM) will be given in this paper. Five main sources of uncertainty (measurement chain, operating conditions, meteorological conditions, receiver location and residual noise) are combined to determine the overall uncertainty. Keywords: environmental noise, measurement, uncertainty 0 INTRODUCTION Noise can be define as an unwanted or undesired sound whereas environmental noise is any unwanted or harmful outdoor sound created by human activities that is detrimental to the quality of life of individuals. Worldwide, 130 million of people are exposed to environemtal noise levels above 65 dB(A), while another 300 million live in uncomfortable environmental noise levels (55 dB(A)-65 dB(A)) [1]. Although by listening we detect noise with a great sensitivity, we have often difficulties to describe it and we certainly cannot define it in technical terms - we usually know when noise is excessive, but we cannot predict the required noise reduction and, more important, we cannot determine how to effectively reduce the excessive noise. The proper environemtnal noise pollution assessment and design of effective noise control measures require noise measurement. Noise measurement is an important diagnostic tool in noise control technology and noise pollution assessment. The objective of noise measurement is to make accurate measurement which gives us a purposeful act of comparing noises under different conditions for assessment of adverse impacts of noise and adopting suitable control techniques for noise reduction. It is well known that environmental noise levels can vary over a wide range as a result of the diversity of site conditions and activities occurring during field measurements. Environmental noise very often occurs in the form of randomly fluctuating sound signals. To quantitatively describe this phenomenon, noise index such as equivalent pressure level L eq is widely used. The measured value of L eq based on the sound pressure level measurements by sound level meter will probably differ from the true one due to the effects of the errors throughout the experiment chain and in the physical phenomenon under study. In most physical experiments there will be a random component affecting to environmental noise measurement uncertainty. A number of authors have already made significant contributions in the field of environmental noise measurement uncertainty determination [2,3]. Guidelines on estimating the measurement uncertainty in compliance with the ISO Guide to Uncertainty in Measurements (GUM) explained in a series of JCGM (“Joint Committee for 39