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The article discusses the requirements for determining airborne sound insulation according to ISO 10140-2, which involves measuring sound pressure levels in the source (L1) and receiving (L2) rooms, as well as reverberation time measurements in the receiving room. The size of the free test opening and the equivalent sound absorption area in the receiving room affect the value of L2. While ISO 10140-5 specifies the dimensions of a full-size test opening, reduced-size openings can also be used. However, testing reduced-size baffles with specific dimensions may be necessary, and measurements on rectangular-shaped baffles may yield higher sound reduction indices than square-shaped ones. The article presents a comparative analysis of the spectral characteristics of different types of single homogeneous baffles with various dimensions using experimental methods. It examines the measurement methodology's influence on determining sound insulation spectra and the weighted sound reduction index Rw. The article also calculates the combined uncertainty in determining the sound insulation properties and partial uncertainties in determining L1 and L2. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The main problem in the measurement of airborne sound insulation is the measurement of the sound power radiated by the barrier, in practice performed by measuring the sound pressure level and the acoustic absorption in the receiving room. Large variations of the sound pressure level in a reverberation room indicate the presence of dominating strong standing waves, so that it becomes necessary to install diffusing elements. In ISO 10140, the limits have been defined in which the reverberation time at frequencies at and above 100 Hz should be included. Sometimes, however, in the case of rooms with a large volume, obtaining the required parameters is difficult and sometimes even impossible. It should then be checked whether the measured sound insulation depends on the reverberation time. The paper presents the results of sound insulation measurements at various reverberation time lengths in subsequent stages of diffusing elements installation in the receiving room. An analysis of diffusing materials amount and arrangement influence on the uniformity of the sound pressure level distribution and reverberation time in the room as well as the value of the measured sound insulation was carried out. Uncertainty of sound insulation measurement with partial uncertainties was adopted as a criterion supporting the assessment of the obtained results. [ABSTRACT FROM AUTHOR]