Sound transmission through triple plates separated by air cavities in the low-frequency range

Abstract

A theoretical study of sound transmission in rigid duct through clamped triple plates separated by two impervious air cavities is formulated. The vibrating motion of the plates and the sound pressure field are expanded in terms of an infinite series of the modal functions. The accuracy of the theoretical predictions is first checked against experimental and numerical results, with good agreement achieved. The model predictions are then used to explore the influence of key parameters on the sound isolation capability of the triple-plate configuration, including the thickness of the plates and that of the air cavities. Furthermore, the sound transmission loss (STL) of the triple-plate model is compared with that of a double plate. Results showed that replacing the double plates with three plates while keeping the air cavity gaps between the plates the same degrades the STL in the low-frequency range. However, using the triple plates is more suitable to enhance the sound insulation performance when enough space is available.