Ultralight Single‐Walled Carbon Nanotube Aerogels for Low‐Frequency Sound Absorption

Abstract

Absorbing low-frequency sound below 1000 Hz with an ultralight material is a critical challenge. Nanofibrous sound-absorbing materials have many interfaces for air-borne sound loss. In addition, nanofibers with a high elastic modulus can increase the loss of sound propagating in the solid, enabling good, lowfrequency sound absorption. Herein, a composite aerogel based on singlewalled carbon nanotubes (SWCNTs) and carboxymethyl cellulose (CMC) as an ultralight material that effectively absorbs low-frequency sound is reported. This ultralight aerogel has a hierarchical porous structure composed of highmodulus SWCNT-CMC composite nanofibers. A sample with an areal density of 20 mg cm À2 (bulk density: 5 mg cm À3 , thickness: 39 mm) achieves a soundabsorption coefficient of 0.44 at 500 Hz. The sound-absorption behavior is sufficiently described by the Biot-Johnson-Champoux-Allard model, indicating the significant effect of the high elastic modulus of the nanofibers on the soundabsorption performance. The article presents a new design principle for ultralight materials with low-frequency sound absorption that takes into consideration both the porous structure and the elastic modulus of the material framework.

Fabrication, sound absorption simulation and performance optimization of multi‐layer gradient fiber‐based composites

“…It is not difficult to find that decreasing the diameter of the perforations is more conducive to the propagation of the sound waves in the structure, which leads to further dissipation of the sound waves in the S‐A 33 . Compared with other reports, 42‐46 the gradient composites prepared in this study is more conducive to practical production and application due to their high noise reduction capability, thin thickness (as shown in Figure 8D), simple processing, and low cost.…”