Bioaerogels for Ultra-Broadband Perfect Acoustic Absorption

Abstract

Noise has become the world's second-largest environmental risk factor1-3. The simultaneous achievement of ultra-broadband and perfect acoustic absorption is a quite vital yet long-standing challenge4-11. Herein, we propose a new "gradient pore circulation (GPC)" strategy for building hierarchical ordered architecture of bioaerogels, by using highly active microfibers precisely dissociated from the wood S2 sublayer as basic units. The bioaerogels comprise anisotropic parallelly-layered microchannels, enriched with intricate multilevel pores within each layer, alongside abundant spring-shaped strips bridging these adjacent layers. Under the “GPC” strategy, the soundwaves effortlessly enter the parallelly-layered microchannels possessing moderate flow resistance, while the synergy of long microchannels, multilevel pores, and abundant interlamellar strips create plentiful closed loops, fostering a repetitive cyclic reflection‒friction‒dissipation of soundwaves. The bioaerogels achieve near-perfect acoustic absorption abilities, with a sound-absorption-coefficient of 0.95~1 across an ultra-broad frequency range of 520‒6300 Hz and a superb noise-reduction-coefficient of 0.82, the highest recorded to date. More importantly, the sound absorption properties retain almost unchanged at extreme temperatures (‒60~+60 ºC) over three months. The revolutionary bioaerogels hold great promise as sustainable sound absorption materials for diverse applications.