SOUND TRANSMISSION LOSS ACROSS A DUCT SECTION INSTALLED WITH COUPLED SIDEBRANCH ARRAYS UNDER NO-FLOW CONDITION

摘要

Sidebranch array has been proposed to be an effective wall-mounted duct silencer. It is composed by a series of side-branches with different lengths in order to create broadband sound transmission loss. It has been shown that coupling sidebranch arrays on opposite sides of a duct can provide strong and broadband sound transmission loss. In the present study, the effects on the sound transmission loss by changing the positions of these arrays are simulated. The result shows that the arrays under normal arrangement (that is, the longitudinal position of the highest tubes of the two coupled sidebranch arrays are the same) can double the effective bandwidth of sound transmission loss compared to the performance of a single wall-mounted array on one side of the duct. More high frequency noise is attenuated at the same time. In terms of broadband sound transmission loss, the normal arrangement of the arrays is much better than the reverse arrangement (the order of tube arrangement of one of the arrays is reversed). The latter cannot cover one tenth of the effective bandwidth of the former. This finding provides clue for enhancing the performance of the sidebranch array silencer.