N ANOSTRUCTURED materials are an important subject in different applications. Zinc oxide (ZnO) nanoparticles have much attention because of their unique properties. The objective of this work is to synthesise zinc oxide nanoparticles by simplest chemical method (direct aqueous precipitation). Also, the effect of zinc oxide addition to polyurethane foam (PUF) on the mechanical and sound properties has been evaluated. Different concentrations of ZnO (0.25, 0.5, 1, 2 and 3 wt.%) were used. ZnO nanoparticles were characterized by some techniques such as X-Ray diffraction, Energy dispersive X-ray spectrometry and Transmission electron microscopy analysis. Scanning electron microscope was used to describe the dispersion state of the nanoparticles in the polyurethane foam. Density of PUF increased while the particle size decreased. Finally, it was confirmed that the mechanical and acoustic properties of polyurethane nanocomposites were improved and depend on the amount of nanozinc oxide.

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.