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Using MLS methods in laboratory measurement of airborne sound insulation

100%

Mleczko D.

tom Vol. 32, nr 2

art. no. 2021205

Following the requirements of ISO 10140, to determine the acoustic insulation, measurements of the sound pressure levels in the source (L1) and receiving (L2) rooms and the reverberation time measurements in the receiving room (T) should be performed. However, the standard does not indicate the measuring signal to be used for the measurements. Various measurement methods can be used, including the use of the broadband noise or MLS method. The article examines the influence of the applied measurement methodology on the determined spectra of acoustic insulation and the weighted sound reduction index Rw. The total uncertainty of determining the acoustic insulation properties and partial uncertainties in determining L1, L2 and T were also calculated. The analysis of the obtained results allows concluding that the applied measurement method has no significant impact on the obtained acoustic insulation values, and the obtained measurement differences may rather be the result of an insufficient sample size.

Analysis of the Usefulness of Measurement on a Board at Ground Level for Assessing the Noise Level from a Wind Turbine

51%

Wszołek T. , Pawlik P. , Mleczko D. , Chronowska J.

2020

tom Vol. 45, No. 1

165--175

The specific working conditions of the wind turbine in strong wind cause a number of problems in the measurement of noise indicators used in its short and long-term assessment. The wind is a natural working environment of the turbine, but it also affects the measurement system, moreover, it can be a secondary source of other sounds that interfere with the measurement. One of the effective methods of eliminating the direct impact of wind on the measurement system is placing the microphone on the measurement board at ground level. However, the obtained result can not be directly compared with the admissible values, as it has to be converted to a result at a height of 4 m. The results of previous studies show that this relation depends, inter alia, on the speed and direction of the wind. The paper contains the results of measurements on the measurement board, according to EN 61400-11:2013, and at a height of 4 m above ground made simultaneously in three points around the 2 MW turbine at various instantaneous speeds and changing wind directions. Analysis of the impact of measuring point location on the measurement result of noise indicators and the occurrence of additional features affecting the relationship between the values measured on the board and at the height of 4 m, and especially the tonality, amplitude modulation and content of low frequency content, was made.

Experimental verification of the usefulness of selected infrasound and low-frequency noise (ILFN) indicators in assessing the noise annoyance of wind turbines

38%

Wszołek T. , Mleczko D. , Pawlik P. , Kłaczyński M. , Małecki P. , Stępień B.

tom Vol. 33, nr 3

art. no. 2022315

This paper presents an overview of the indices used in evaluating ILFN noise, based on C and G weighting curves and LC-LA difference parameter, as well as curves compared to the loudness threshold curve. The research section includes measurement results of wind turbine (WT) noise along with proposed indicators for evaluating this noise in the infrasound and low-frequency bands at distances of 250 m, 500 m and 1000 m from the turbine. The results obtained indicate low noise levels in the infrasound band, lower than the threshold curves from a dozen or so dB in the upper part of this band to nearly 60 dB in the lower part. The LC-LA indicator has been shown to be of poor utility for evaluating low-frequency noise, with the LG indicator reasonably useful for evaluating infrasound noise.