Using MLS methods in laboratory measurement of airborne sound insulation

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.