Abstract. In structures, airborne sound insulation is utilized to characterize the acoustic nature of barriers between rooms. However, the assessment of sound insulation index is once in a while troublesome or indeed, even questionable, both in field and laboratory measurements, notwithstanding the way that there are some unified measurement methodology indicated in the ISO 140 series standards. There are issues with the reproducibility and repeatability of the measurement results. A few troubles might be brought on by non-diffuse acoustic fields, non-uniform reverberation time, or blunders of the reverberation time measurements. Some minor issues are additionally postured by flanking transmission. In this paper, investigation of the uncertainties of the above specified measurement parts and their impact on the consolidated uncertainty in 1/3-octave frequency band. The total measurement uncertainty model contributes several different partial uncertainties, which are evaluated by the method of type A or type B. Also, the determination of the sound reduction index decided by ISO 140-4 has been performed.

Primary calibration method is used by relatively few laboratories such as national calibration laboratories and few large automotive, space, or governmental organizations, which work at high technological level. The National Metrology Institute of Egypt (NIS) has developed a pressure calibration system that used for calibration of pressure sensitivities. In this study, we estimate the uncertainty of unknown one inch condenser microphone using two known references one inch condenser microphones according to international standard. IEC 61094-2009 gives more information's and details on the uncertainty calculations. In this method, a wide frequency range with a high accuracy and repeatability were achieved.

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Nowadays, lightweight building structures are widely used by the construction industry as a more natural and cost-effective method. The purpose of this study is to compare between sound pressure level and vibration velocity method for sound reduction index determination for single-and double-leaf gypsum board partitions. The sound pressure level method was carried out according to the requirements of ISO 140-3:1997, and the vibration velocity method (V) was carried out according to some criteria of ISO 10848-1:2006. Regarding double-leaf partitions, measurements were carried out with the leaves separated by 5-and 10-cm air gaps. The effect of cavity filling with absorbing materials was studied experimentally. The space between the leaves was filled with Rockwool and polyurethane to illustrate the effect of cavity absorption on the sound reduction index behavior. It was found that there is good agreement between the two methods. Also, cavity filling with a 10-cm absorbing material such as Rockwool increases the sound reduction index at the critical frequency by 7 dB using sound pressure method and 4 dB using vibration velocity method.