Optimization of hybrid microperforated panel and nonuniform space-coiling channels for broadband low-frequency acoustic absorption

Broadband noise cancellation at low frequencies (<1000 Hz) with thin absorbers has been a long-standing demand in acoustic engineering. Here, a design method is proposed for a subwavelength hybrid absorber, consisting of a microperforated panel (MPP) backed by nonuniform space-coiling channels. The low-frequency absorption performance is analyzed by impedance theory and complex frequency method. The sensitivity of the absorption band to the parameters of the MPP and the coiled channels is investigated, based on which a genetic algorithm is employed to costume quasi-perfect absorption at the desired frequency. Furthermore, a parallel integration of multiple inhomogeneous units is developed to broaden the absorption spectrum. An optimization strategy is proposed to effectively mitigate the performance degradation caused by the impedance coupling effect. The influence of the number of combined units and the objective function is analyzed for the optimization results. Numerical simulations, experiments, and theoretical predictions verify the effectiveness of the design method. Furthermore, the as-designed combination absorber achieves continuous absorption from 305 Hz to 1088 Hz. The proposed design approach may offer a promising solution for practical applications in broadband noise reduction.