Sound Absorption and Transmission in Nanoengineered Polymers

In this study we use vapor deposition to incorporate carbon nanotubes (CNTs) and silicon dioxide nanopowder (nanosilica) in Polyurethane (PU) as well as to engineer Parylene C (PC) in a microfibrous thin film (µFTF) and bulk forms in an attempt to examine acoustic absorption and transmission properties in the low frequency (50 to 200 Hz) range. Incorporating CNTs or/and nanosilica into PU significantly increases its acoustic transmission, presumably due to increased rigidity caused by nanoparticle (CNTs and nanosilica) addition. This is explained as due to adding nanosilica or/and CNTs to PU increases its rigidity and, hence, its sound transmission. On the other hand, engineering the PC in the µFTF form enhances acoustic absorption in the film, especially at the resonant frequencies associated with oscillations of the microfibers making up the PC µFTF.