Vibro-acoustic analysis of an elastically restrained plate duct silencer backed by irregular acoustical cavity

Drum silencer is seemed as a novel passive mean for the low frequency noise control in duct, a lot of research work has been done for such panel silencer backed by regular cavity, while there is little effort devoted to the case with wall inclination. Motivated by such limitation, a three-dimensional vibro-acoustic coupling model for sound attenuation analysis of elastically restrained plate silencer backed by irregular acoustical cavity is established in a unified energy formulation. Coordinate transformation technique is employed to map the acoustical field description associated with the irregular-shaped cavity into those defined in a unit cubic volume. Boundary smoothed supplementary terms are introduced to the Fourier series to construct the corresponding admissible function, in conjunction with Rayleigh-Ritz procedure, the fully coupled matrix is derived, in which the concrete block can be specified for the irregular cavity subsystem. Numerical results are presented to illustrate the correctness and effectiveness of the proposed model through the comparison with those calculated from Finite Element Analysis. Based on the model established, the influence of geometry distortion of backed cavity on sound attenuation behavior of such drum silencer is studied and addressed. It is found that the wall inclination arrangement can modify the duct-panel-cavity structural-acoustic coupling pattern, and further serve as the optimal parameter to adjust the transmission loss frequency band. Experimental study is also carried out to verify the theoretical prediction from current model.