Investigating the effect of a hybrid muffler on the sound attenuation of a small gas generator

In this study the effect of a hybrid muffler on sound emitted of a small gas generator which has been covered by an acoustic enclosure was investigated. The specifications of a reactive muffler were calculated according to the recommendation of ASHRAE 2.6 committee and 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 modes 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 the 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 dB and 26 dB, respectively. The overall A-weighted generator sound was in the range of 73.2-85.8 dB(A) for all loading conditions and sides by using HM. The acoustical performance of HM on the side with the maximum generator sound (in front of the exhaust) 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.