This research work was to study the effect of surface treatment of natural fiber and the effects of type and content of natural fiber on the development of acoustic material from natural rubber foam /natural fiber composites. The surface treatment used for this research work was sodium hydroxide (NaOH) treatment. NaOH Concentrations and treatment times were varied from 0 to 15 %wt. and 0 to 30 min respectively. Natural fibers used for this work were bagasse fiber (BF) and oil palm fiber (OPF). The suitable condition for surface treatment was estimated by fiber length and diameter (L/D) ratio and morphology of natural fiber. The result suggested that L/D ratios tended to increase when NaOH concentrations and/or treatment times increased except for NaOH concentration of 15 %wt. L/D ratios of OPF after surface treatment were changed more than those of BF. The suitable conditions of NaOH treatment for BF and OPF were NaOH concentration of 10 %wt. and surface treatment times of 30 and 10 min respectively. The effects of fiber type and content on sound absorption properties of natural rubber foam /natural fiber composites were investigated by cell characteristics sound absorption coefficient DMA analysis and bulk density. Both treated BF and OPF with suitable treatment condition were varied from content of 0.0 to 10.0 %wt. The result showed that the cell size of composites tended to decrease with addition of natural fiber whereas number of foam cell per unit volume increased. After adding natural fiber more than 2.5 %wt. cell size of composite foam and number of foam cell per unit volume tended to change the inverse direction. Natural fiber in composites enhanced the sound absorption efficiency. Sound absorption coefficient of composites adding BF was more than that of composite adding OPF. The addition of natural fiber enhanced the elasticity of composites and that increased sound absorption efficiency. NaOH treatment led to creation of strong interfacial bonding between natural fiber and natural rubber and enhanced the sound absorption efficiency. Density of NR composite foam increased with increasing natural fiber content.

Nowadays the majority of environment problem is pollution of vehicle including the noise of engine combustion. For this reason this thesis aims to compare and study the parameters which affect noise reduction on exhaust pipe. Not only reduce the noise pollution but also maintain the efficiency of the engine. These two substances must be considered. Therefore the researcher emphasized to study the parameters on 3 types of muffler with an equal volume: direct reverse and offset type of mufflers. Initiated by data collection the pressure and the velocity in muffler at the speed of engine at 1000 RPM (slow-running engine mode) and 4000 RPM (maximum running engine mode) were investigated. The data were applied into the program that called “SolidWorks” in order to study parameters. In this step the relation between the pressure and velocity of exhaust were represented. In addition the muffler models were selected to manufacture and test by the standard of The Department of Land Transport. As a result there are two major parameters of the muffler. Firstly the metamorphism of the exhaust gas flow direction pleasurably causes the lower noise at the speed of engine at 1000 RPM. Besides an increase of the flow gas distance can diminish noise at the speed of engine at 4000 RPM as well. However this muffler models were tested under the working mode of catalytic device that is standard equipment for automotive vehicles.

This article presents texture analysis of crispy snack products by using Acoustic Emission (AE) to measure sound that occurred when the products were chewed or broken. This technique has currently gained great interest from food scientists. A sound emitted from food was found to be related with microstructure and crispness. Measurement of sound emitted from food when it was chewed consists of three main steps: 1) Apply force on piece of food with a texture analyzer; 2) Detect sound signal with an acoustic envelop detector; and 3) Interpret the collected data of mechanical force and acoustic emission.

At present most human-related products contain a mixture of chemicals for inhibiting microorganisms polluting the environments and harming the users. The purpose of this research was to develop a product using banana and papaya peel extracts as replacers for the chemicals inhibiting microorganisms in heel cream. By extracting raw bananas and papaya peels with coconut oil the studying the efficacy of inhibition on E. coli S. aureus Aspergillus sp. and S. cerevisiae with Disk Diffusion method at the protein concentration were performed as follows: 25 50 100 and 150 micrograms per milliliter. The observation of clear zone to observer clear zone of inhibition. and the Turbidity method using light absorption at a length of 600 nm was also were shown the corresponding results of microbial inhibition. observed and showed the consistent results. Especially the papaya extract having the protein concentration at least of 150 micrograms per milliliter could inhibit all 4 microbe species but could not inhibit S. cerevisiae that indicated a good trend of no harm on human. When mixing the extract in the heel cream it was found that Heel cream containing banana extract papaya and both mixtures displayed the density of 0.9674 0.9103 and 0.8057 gram per cubic meter respectively. They could be stored at room temperature for more than 45 days and still maintained the properties of microbial inhibition by up to 80 percentages. When studying the satisfaction of consumers collected randomly from teenagers to elders at both sexes of 40 people more than 80 percentages of the customers were satisfied with the heel cream from all extracts. These all creams could make the feet soft and moisturized within 1 week. More suggestions were to improve the smell of heel cream products to be suitable for all age of consumers. Therefore this research could be concluded that banana and papaya peel extracts inhibiting microorganisms could be used as a heel cream for further continuously developing at the industrial level.