Aerogels-filled Helmholtz resonators for enhanced low-frequency sound absorption

Aerogels are highly porous materials with diverse properties, such as ultralow density, high specific surface area, and extremely low thermal conductivity. These unique features offer them unparalleled potentials for applications in sound absorption. Here, we present a composite structure for acoustic absorption, which is constructed by filling the designed Helmholtz resonators (HRs) with three types of granular aerogels with various thicknesses (5, 10, 15 and 20 mm). The transmission loss and absorption coefficient are investigated at low frequency range from 200 to 2500 Hz. The measurement results show that the composite structures not only increase the absorption level and bandwidth, but also provide a simple tunability of frequency bands for sound absorption. This novel combination of resonant structure and aerogels paves the route towards designing highly tunable and efficient acoustic composite devices for noise absorption in vent and pipeline systems. (C) 2019 Elsevier B.V. All rights reserved.