Analysis of Sound Transmission Loss on Infinite Double-panel Partition

Based on two panels structure model, the theoretical processes of calculating the sound transmission loss (STL) are detailed by wave transfer method (WTM) and structural bending wave method (BWM), respectively. When the acoustic wave is vertically incident and obliquely incident, the sound transmission loss of infinite two-plate structure can be calculated by WTM and BWM, respectively. The calculation formulas and physical meanings of resonance frequency points are given, including the frequencies of “mass-air-mass”, standing wave, and panel coincidence. Through some comparisons of STL curves and analysis about the trends of two curves, the advantages and disadvantages of WTM and BWM are pointed out. The equivalent conditions of WTM and BWM are derived, in the case that the acoustic wave is vertically incident on the thin plate structure. When the structure and acoustic wave satisfy the equivalent condition, the STL curves provided by WTM and BWM are consistent with each other under vertically incident wave; when plane acoustic wave is obliquely incident on whole structure, it becomes inaccurate for the calculated result by WTM, while it is still reliable for the results by BWM. By changing the plate thickness, air layer thickness and elevation angle of incident acoustic wave, some influences created by these factors on STL of infinite two-plate structure are analyzed.