Effect of the Number and Stacking Sequence of Membranes in Glass Fiber Felt Composite Structure on Acoustic Properties

In this paper, we investigate the effect of the number and stacking sequence of membranes in different glass fiber felts and their corresponding composite structures (bilayer structure and sandwich structure) on acoustic properties. Sound absorption coefficient (SAC) and sound transmission loss (STL) are measured by a B&K impedance tube. The results show that, with the increase the number of membranes in glass fiber felt composite structures, which can effectively improve the STL. For the sandwich structure, the greater the number of membranes is, the better the STLs are. However, STL of sandwich structure improves a little with the increase the number of membranes. Stacking sequence of membranes has an effect on the total STL. STL of different glass fiber felts front with a single-layered membrane is better than that back with a single-layered membrane. However, SAC of glass fiber felts front with a single-layered membrane is worse than that back with a single layered membrane. This phenomenon is also found in bilayer structure and sandwich structure. The optimal stacking sequence of membranes for STL is the membranes in front of composite structures, i.e., close to the sound incident surface of composite structures.