Sound transmission loss of double plates with an air cavity between them in a rigid duct

Abstract

In this paper, the sound transmission loss (STL) of thin double plates with an air cavity between them in a rigid duct is considered using an analytical approach. The vibration motion of the plate and sound pressure field are expanded in terms of an infinite series of the modal functions. Under the plane wave condition, a low frequency solution is derived by including the first few symmetric modes. It is determined that the peak frequencies of the double plates coincide with those of each single plate. When the two plates are identical, the STL becomes zero at the natural frequencies of the single plate. However, when the two plates are not identical, the STL is always greater than zero. The location and amplitude of the dips are investigated using an approximate solution when the cavity depth is very small. It is observed that dividing the single plate into two plates with an air cavity in between degrades the STL in the low frequency range, while the equivalent surface mass density is preserved. However, when the cavity depth is not small, the STL of the single plate can be smaller than that of the double plates.

An investigation on transmission loss of clamped doubled thin plate with added mass

“…Symbols with subscript 2 have the same meanings as defined above but applied to panel 2. e mn , b mn , c mn , d mn and A are amplitude constants related to the waves in the duct as shown in Figure 1. This is given by Kim et al [7]:…”

“…The experiment samples were attached to a sample holder in the tube to provide a reliable boundary condition for each experiment. Firstly, the present model is compared with results of Kim et al [7] for plywood plate in Figure 3(a). The theoretical model for Kim et al for rectangular plate was modeled using the parameters given, and the present model agree well for all frequencies.…”

Prediction of acoustic wave transmission features of the multilayered plate constructions: A review

“…The results showed that the flexural vibration of a plate increased the acoustic absorption performance of the structure in water. In another work [299], the STL of a thin panel equipped with a cavity in a rigid duct was calculated. Herewith, the dynamic behavior and acoustic pressure were developed as an infinite series of modal functions.…”

Enhancing the sound transmission loss in double-leaf partitions with lateral local resonators substructure

“…The motion of the panels was modeled in space-harmonic expansion as described by Mead and Pujara. 7 It should be noted that several authors have reported the limitations of double-wall structures at low frequency in the region of mass air mass resonance, at which the model for infinite panels delineate an out-ofphase motion 2,8,9 Thus, numerous methods are being investigated to enhance double walls for better STL. One of such methods adopted is the filling of the cavity of the double wall with filler materials.…”

“…It should be noted that several authors have reported the limitations of double-wall structures at low frequency in the region of mass air mass resonance, at which the model for infinite panels delineate an out-of-phase motion 2,8,9…”