Development of combined resistance muffler for reduced noise of farm tractor

Abstract

A farm tractor is the most important component of farm mechanization. Farm tractor noise, on the other hand, has a negative impact on human health. The exhaust system produces the most noise of all the noises produced by a tractor. A muffler is an acoustic filter that is used to reduce exhaust noise. Perforated ducts, baffles/perforated baffles, expansion chambers, and longer inlet/outlets are used to make mufflers. A person working in a workplace with a noise level of 90 dBA is limited to 8 h of work each day under the Occupational Safety and Health Act (OSHA, 1983). As a result, utilizing the finite element approach and acoustic theory, an existing muffler (Reactive type muffler) was optimized to a combined resistance muffler after installing in a 47.6 PS, 2200 rated RPM three-cylinder diesel engine. Except for the frequency range of 138–455 Hz, 515–851 Hz, and 1524 Hz, the optimized combined resistance muffler had a considerable increase in transmission loss in all other frequency ranges. The improved muffler's mean transmission loss was 3.77 dB higher than the original muffler's in the 0–2000 Hz range, which indicates notable improvement in the noise canceling effect. The noise reduction of this combined resistance muffler was tested at operator ear level (OEL). Near rated engine speed, the combined resistance muffler suggests a noise reduction of 1.2 dBA–1.9 dBA over the existing muffler. The upgraded muffler also served as a benchmark for similar muffler structural improvements.