Enhanced transmission loss in acoustic materials with micro-membranes

Due to their strong transmission loss (TL) at low frequencies, acoustic micro-membranes (AMMs) have been the subject of many studies. In this paper, a theoretical model for AMMs is established which gives a direct insight into their sound insulation qualities. Analysis of the model's acoustics shows how the sound insulation provided by a membrane can be significantly enhanced, and reveals the intrinsic characteristic of AMMs in mid-low frequency range. Further analysis on two AMMs separated by an air gap gives a quantitative description on how performance varies with the air gap. Using the theoretical model developed here, it is a straightforward matter to adjust an AMM's parameters to achieve a desired level of attenuation. This work opens the way for the potential application of AMMs in noise control engineering.