Preparation of lamellar-structured carboxymethyl cellulose aerogels for efficient sound absorption

Noise is an invisible killer that affects human physical and mental health. Relatively thick layers of porous materials are needed to achieve good absorption at low and medium frequencies. However, increasing thickness leads to increasing weight which may be a problem for several applications. In this paper, carboxymethyl cellulose (CMC) aerogels with lamellar structure were successfully prepared by directional freeze-drying of hydrogels with multilevel network structure to achieve efficient absorption of noise. Here, the influence of the gram weight, thickness, functional particle type and content of the aerogel on its sound absorption properties was discussed. The test results showed that the lamellar structure aerogel with a density of 32.1 mg/cm3 had good noise reduction performance (noise reduction coefficient of 0.42). The reason for this phenomenon was that the structure increased the contact area between the sound wave and the material, which contributed to the absorption of sound energy. Here, it was worth noting that the vermiculite enhanced the conversion of sound energy by enhancing the internal dissipation of the lamellar structure, thus freeing the low-frequency sound-absorbing properties of aerogels from their dependence on the thickness and gram weight of the material. This micro-structured material is flexible and lightweight, which makes it ideal for reducing cabin noise and regulating room reverberation.