Effects of porous materials in an insert earphone on its frequency response -experiments and simulations

This article presents a promising approach to customize the sound-pressure response of an insert earphone by delicately tuning the acoustic impedance of porous materials in it. The effects of applying porous materials on and in various parts in the insert earphone were tested experimentally to determine the resulting sound pressure responses. An equivalent circuit model (ECM) is also presented to simulate the sound-pressure-level (SPL) response of the insert earphone. For each part of the earphone, the effect of applying porous materials was simulated using the ECM approach. For porous elements, modified formulae with correction factors are proposed to determine the acoustic impedance. Comparisons of the simulated responses with experimental data have verified the veracity of the ECM simulations. The present work has verified the feasibility of adjusting the aeration of the porous materials to customize the resulting SPL response of an earphone.