The transmission loss of double expansion chamber mufflers with unequal size chambers

Abstract The double expansion chamber muffler is a commonly used silencing element in duct noise applications. The transmission loss for the case of equal size chambers is known and easily calculated. A closed form expression for the transmission loss for the case of chambers of unequal length and area is presented here. It is also shown that significant tuning benefits result with chambers of unequal size. For evenness of response, with a minimum passband, chamber length ratios of 2:1 and connecting tube lengths equal to the shortest chamber are superior.