Enhanced Low Frequency Sound Absorption of Bilayer Nanocomposite Acoustic Absorber Laminated with Microperforated Nanofiber Felt

A laminar nanocomposite sound absorber was fabricated by laminating a microperforated nanofiber felt (MPNF) on a reinforced nanofibrous cryogel. The spatial morphology of both dense and porous nanofiber layers combined with the microperforations employed on the dense layer delivered a sound absorption average (SAA) rating of 0.61. A lower frequency average sound absorption coefficient of 0.56 was achieved when a denser nanofiber felt layer with the incorporation of 1.78% microperforation rate was employed. A highly porous cryogel layer permits excellent mid- and high-frequency absorption coefficients of 0.74 and 0.51, respectively. The nanocomposite sound absorber has a remarkable areal density of 771 g m–2, making it lightweight and less bulky ideal for acoustic building material. The perforated nanofiber felt, however, has a minimal effect on the sound transmission coefficient (STC) of the nanocomposite sound absorber with an STC of 6.75 dB. By tuning the perforation diameter, perforation rate, and thickness of the nanofiber felt, the overall acoustic absorption performance of the nanocomposite sound absorber can be improved.