An engine mounting system is the primary vibration isolator of the engine from the chassis. The frequency-dependent stiffness and loss factor present a more accurate representation of a rubber mount as opposed to the frequencyindependent damping model. In this article, dynamic optimization of an engine mounting system considering the frequency-dependent stiffness and loss factor is presented. The dynamic properties in all three principal directions are measured on the basis of the optimum locations and orientation angles of the individual engine mounts, which are identified to minimize the mean force transmissibility of the system for a range of frequencies, resulting in a 45% reduction in the vertical transmissibility to the installation base. In comparison, optimization based on a frequencyindependent stiffness underestimated the peak transmissibility, and minimization of the vertical force transmissibility created a significant increase in other directions. The optimum parameters are applied to a small utility two-stroke engine. A significant reduction in the transmitted force and engine displacement is demonstrated.

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The cavity inside microphone of two-way radio can induced noise when involved in outdoor and windy condition. An investigation was performed in Viwika wind tunnel involving a flow visualizations techniques to clarify the flow noise behavior generated by the wind, particularly within the cavity. A smoke wire test was conducted using a cavity model at varying aspect ratio (L/D) between 0.7 and 3 in angle of attack of 0º with Reynolds number of 7831. A two-dimensional Computational Fluid Dynamic (CFD) models based on k-Epsilon turbulence model were conducted to validate the flow visualization result. The results revealed that the deep cavity with an aspect ratio (L/D) of 0.7 produced a single clockwise vortical flow structure and the aspect ratio (L/D) of 3 show the complex flow structure which two recirculation flow vortices were produced inside the cavity. The flow behavior in the CFD simulation was similar to the smoke test. It is shown the flow behaviour inside cavities was control by the aspect ratio (L/D).

This paper presents the sound and vibration damping properties of nonwoven flax reinforced acrylic based polyester composites. This research attempt to solve the problem of synthetic fibre which caused environmental problems. the goal of is study to characterize the sound absorption and damping properties of the natural fibre at difference thickness and pressure. the nonwoven flax reinforced acrylic based polyester composites are produced by using moulding machines at different compression pressures that are 10, 20 and 30 bars. the thicknesses of samples used in this study are 2 mm and 3 mm. the measurement of sound absorption of the material is carried out using impedance tube. For the sample with 2 mm thickness, the result shows that the maximum sound absorption of 0.93 was observed at frequency of 853 Hz and pressure of 20 bars. Damping values are calculated and measure for each sample. the result shows that damping factor is obtained is 0.039 and 0.052 for thickness materials of 2mm and 3mm.

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