High performance broadband acoustic absorption and sound sensing of a bubbled graphene monolith

Noise pollution has been recognized as having significantly negative impacts on people's daily lives and thus the development of high-performance sound-absorbing materials is attracting increasing attention. Here, a multifunctional bubbled graphene monolith (BGM) is developed to have highly efficient and wide frequency acoustic absorption, and possesses a density of only 7.5 kg m^-3, the lightest sound-absorbing material reported so far. It exhibits a high normalized absorption coefficient of 0.9 within a considerably wide frequency range from about 60 Hz to 6300 Hz. The excellent acoustic absorption ability is mainly attributed to the enhanced air-viscous resistance damping inside the interconnected hierarchical structures. The high thermal conductivity of graphene and vibration of thin graphene bubble walls induced by acoustic waves are beneficial for sound absorption as well. Impressively, the BGM could also serve as an effective sound sensor to sensitively detect acoustic changes. In addition, the BGM features other superior properties such as moisture insulation, flame resistance and heat dissipation, which make this sound absorber promising for many important applications in various fields.