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This research was carried out to study the acoustic properties of natural organic fibres; kenaf and coir fibres using impedance tube method. Kenaf fibre was used as noise absorber filler in an insulation panel while the coir fibre as reinforcement in the perforated composite panel. The perforated panel was made from coir fibre/polyester composites with coir fibre volume fraction of 10%, 20% and 30%. The perforation area of the perforated panel was also varied at 10%, 20% and 30%. During the processing stage, the kenaf fibre sheet has been treated with PVA and cut into 100 mm and 30 mm diameter sample for low and high frequency test. The density of the coir fibre is determined to be 32.2 g/cm3 while the density of the kenaf fibre is 42.6 g/cm3. The tests were carried out using impedance tube at acoustic lab, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia using ISO 10534-2 standard for noise absorption coefficients to determine their noise absorption coefficient. The results obtained show that the optimum noise absorption coefficient index for kenaf fibre is 0.8 with 10% fibre volume fraction of coir fibre/polyester perforated composites panel at 10% perforation areas.

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This paper presents a study on the sound absorption properties of a single layer date palm fiber based on the flow resistivity. Experimental measurements were carried out to estimate the flow resistivity value using differential pressure tube. The average diameter of the fibers is 0.462 mm. A date palm fiber sample of 25mm thickness is used in this research. The flow resistivity of the date palm fiber sample was found to be 4.26 kPa.s/m2. The flow resistivity was used to calculate the sound absorption coefficient using Delany and Bazley model. The simulation showed that the values of absorption coefficient are small at low frequencies and rising with increasing frequency. To check the effect of flow resistivity on the sound absorption coefficient Delany and Bazley model was simulated for three different flow resistivity values. The simulation results showed that the sound absorption coefficient increases with the increase of the flow resistivity.

The performance of a fuel injector greatly influences the performance of a vehicle engine. An effective monitoring system is capable of detecting damage, instability, and even the life of fuel injector. In this study, a test rig on fuel injector using piezoelectric film sensor has been developed. Three parameters, namely, pulse width at 5, 10, and 15 ms; frequency at 17, 20, and 25 Hz; and pressure at 10, 50, and 70 bar were used for observation. These parameters were set at different combinations to obtain the different injection patterns of the fuel injector. Statistical methods were used to analyze the data, with the aid of the Matlab software. The injection pattern was described using a new I-kaz (Ƶ) statistical parameter, which is intended to provide a simple explanation of the corresponding correlations between the coefficient of I-kaz and the statistical parameters, such as root mean square, Skewness, and Kurtosis, to obtain effective information on the operation state of the fuel injector. The results showed that higher pulse width results in a higher I-kaz coefficient, which also increases with an increase in frequency and varies with pressure; however, the pattern depends on the pulse width. The I-kaz scatter graph against skewness showed a clear pattern among the statistical parameters. The corresponding correlation was useful for monitoring the fuel injector and can be used as a reference for future studies.