Normal incidence sound absorption of an acoustic labyrinthine metal-fibers-based porous metamaterial at high temperature

This work studies the sound absorption performance of acoustic labyrinthine porous metamaterials (ALPM) at high temperature. The proposed metamaterial is constructed by perforating a homogeneous metal-fibers-based porous matrix with folded slits. These macroscopic perforations provide long channels for sound waves to enter the structure, allowing sound waves to enter the porous material due to the pressure diffusion effect, resulting in excellent subwavelength absorption at high temperatures. Based on the double porosity theory and temperature-dependent parameters, we develop a high-temperature theoretical model and validate it by numerical method. The results show that with the increase of temperature, the peak frequency of the ALPM moves to higher frequencies and the half-absorption bandwidth becomes wider. The discussion of sound absorption mechanism based on the pressure distribution results shows that with the increase of temperature, the pressure diffusion effect exists in a wider frequency range, which helps to suppress the propagation of long-wavelength sound waves at high temperature. The study of particle vibration velocity and energy dissipation density shows that the higher the temperature, the stronger the motion of air particles, and more sound energy is dissipated in the porous material, resulting in enhanced sound absorption. The ALPM can be regarded as a combination of homogeneous porous material and space-coiled resonator. Compared to these two components, the ALPM exhibits excellent sound absorption in the frequency range of 200Hz to 600Hz, especially at high temperatures. The proposed porous metamaterials show promising applications in low-frequency sound absorption at high temperature.