The effect of using passive hybrid muffler on a small generator set noise fuelled by natural gas

A detailed experimental study has been conducted to evaluate the effect of a hybrid muffler (HM) installation on sound emission of a small generator set fuelled by natural gas, which was covered by an acoustic enclosure. Specifications of a reactive muffler were calculated according to recommendation of ASHRAE 2.6 technical committee and based on an appropriate muffler was selected. The selected muffler was added to the muffler installed by manufacturer on generator (GM) and formed hybrid muffler (HM). The sound of generator set was measured for GM and HM setups on four sides of the generator at five different loading conditions (0, 25, 50, 75 and 100% load) using a sound level meter. The results showed that application of HM could reduce the sound of generator at firing frequency (31.5 Hz) and frequencies greater than 1000 Hz, with the maximum values of 11.7 and 26 dB, respectively. The overall A-weighted generator sound was in the range of 73.2–85.8 dB (A) at all the loading conditions and sides by using HM. The acoustical performance of HM on the side with the maximum generator sound (side 1) increased from 5.1 dB (A) at no load to 10.61 dB (A) at full load conditions. Therefore, the HM usage could be recommended as a useful approach to attenuate the generator sound.