Textile-based directionally antagonistic sound absorber with double gradient structure

In the structural design of sound-absorbing materials, how to combine the merits of porous materials with acoustic functional fillers with special structures to improve the sound-absorbing performance of porous materials at low-medium frequencies is a challenging problem. Herein, a directionally antagonistic acoustic textile is proposed as a sound absorber fabricated via single-sided coating. It is found that the sound absorber presents a double gradient structure by controlling the distribution of filler on the porous material frame. Considering the incident plane of acoustic waves, two different paths are defined, namely A–B and B–A (A, coated side; B, uncoated side), under which the sound absorber shows remarkable anisotropic sound absorption. The peak frequency is from 5559 Hz of bare fabric to 3455 Hz of the A–B NW III (coated nonwoven when sound waves propagate along A–B) sound absorber, showing a significant tendency to move to the lower frequencies. The peak value of sound absorption coefficient of the A–B NW III is 0.94, indicating a high sound absorptivity. In addition, by adjusting the acoustic functional filler and weaving structure and thickness of the base fabric, the sound absorber exhibits the expected anisotropic sound absorption. The novel sound absorber can be fit for lightweight sound-absorbing applications because of the characteristics of light, soft, high efficiency and broadband sound absorption.