Sound Absorbing Properties and Optimization Design of Gradient Porous Metal Fibers in High-Temperature Environments

To characterize the sound absorbing properties of gradient porous metal fibers at high temperature, a theoretical model is developed by introducing the temperature-dependent parameters of air into the Johnson-Allard model. This model is favorably validated by experiments on porous metal fibers at high temperatures. Further, employing acoustic impedance transfer formulation, another theoretical model for multi-layered gradient metal fibers at high temperature is established. By adopting an optimization strategy, the multi-layered gradient metal fibers are optimized for superior sound absorption. The results reveal that the sound absorbing capacity of the material at high temperature is slightly worse than that in normal temperature. With the increase of porosity or fiber diameter, the sound absorption decreases in low frequency range but increases in medium frequency range. The sound absorption capability of the gradient structure is better than that of homogeneous structure with the same thickness, and the optimal sound absorption can be achieved in given specific conditions. This research is helpful for the application and design of the gradient porous metal fibers in high temperature environments.