Low-Frequency Sound Proof Cement-Based Syntactic Foam

Abstract

A low frequency soundproofing cement based material has been developed in this study. This closed-cell composite material basically consists of a cement matrix embedded with in-house developed Cement Spheres (SC) and Cement Hollow Sphere (CHS) or macrospheres. The produced foams known as Cement Syntactic Foam (CSF) were characterized for its' properties including stress-strain behaviour. Acoustic Transmission Loss (TL) test was conducted on two types of CSF, namely CSF-CS and CSF-CHS and the results were compared to plain cement (PC). It was observed that the CSF showed a good mechanical properties and better sound TL in a low frequency range. The significant improvement in the TL was shown by CSF with incorporating CHS. However, no significant increase in the TL was observed with the increasing sample thickness. Overall, it was discovered the produced CSF has potential in the application of lightweight soundproofing material substituting common barrier material. low damping due to the open and interconnected cell structure. The adding of macrospheres also helped in reducing weight, thus lower the density . Unlike other assembly wall materials, the CSF does not rely on the mass law . The mass law equation (3), predicts that each time the frequency of measurement or the mass per unit area of a single layer wall is doubled, the TL increases by about 6 dB. The mass per unit area can be increased by increasing thickness or by selecting a more dense material. However, this study found otherwise and similar observations were found in a closed-cell aluminium foam (4), (5). Therefore, in comparison to conventional concrete, the CSF has the advantages of low density, low water absorption, good mechanical strength and damping properties. Moreover, the addition of macrospheres, provide better energy absorbing mechanism, thus improving the compressive toughness of the system. Because of its special feature, this study was carried out to study the potential of the prepared CSF in sound proofing application.