Hybrid sound-absorbing foam materials with nanostructured grit-impregnated pores

A new approach to the design of sound-absorbing materials was experimentally investigated. Improved acoustic properties were obtained in a wider frequency range through the impregnation of nanoporous grit into foam pores. Using this approach, the range of efficiency of these materials was extended from high frequencies of 2.0-6.3 kHz to a lower band of 0.5-1.6 kHz. The absorption ratio was increased by 60-100%, and the transmission loss was increased by 20-22 dB.