Noise Attenuation Characteristics of a Power Tiller forDifferent Surfaces in Transportation Conditions

摘要

Power tillers are the agricultural machines, which are fitted with small diesel engines.Besides their on-farm application in Iran, they are also engaged in transportation of agriculturalproducts and human beings on the grassland, asphalt, and dirt rural roads. In spite of their noiseadverse effects on operators and bystanders, limited information is available concerning the noiseinvestigation of this machine. So the objectives of this research were to study the noise propagationtrends as well as noise attenuation characteristics of power tillers on different surfaces intransportation conditions. The power tiller used in this study was fitted with a 13-hp diesel engine.During measurement and recording the sound pressure signals of the power tiller, the variables ofengine speeds and gear ratios were varied to cover the most normal range of the power tilleroperation in transportation conditions for the asphalt, dirt rural roads, and grassland. The test siteswere prepared according to SAE noise measurement test procedures. The results show that themaximum attenuation effect of grass cover for bystander position is in the range of 350-700 Hz. Theoverall noise in this case is about 2.5 dB (A) lower than the asphalt and dirt rural roads. Themaximum overall noise measured at driver ear’s position at different gear ratios in asphalt, dirt ruralroads and grassland was about 92 dB (A) for 2200-rpm engine speed, which is upper than allowablenoise exposure prescribed by NIOSH.