Material Characterization of Multi-Layered Noise Control Treatments from Random-Incidence Transmission Loss

Sound propagation through noise control treatment is governed by fluid, mechanical and geometric properties of the materials. The knowledge of material properties is important to improve the acoustical performance of the resulting noise control products. A method based on optimization together with genetic algorithm is used to estimate material properties of multi-layered treatments. Unlike previous inverse characterization approaches based on normal incidence performance metrics measured using standing wave impedance tubes, the current approach is based on random incidence performance metrics. Specially, the insertion loss ‘measured’ from two room transmission loss suite is utilized. To validate the applicability of the proposed method, numerically synthesized insertion loss computed from known material properties are used. In order to properly represent the ‘measured’ values, noise is added to the numerically synthesized insertion loss values. Additionally, the effect of the number of measurement points on the accuracy of the solutions is also investigated. The utility and applicability of the proposed inverse characterization approach are validated by comparing the estimated material properties to the corresponding ‘actual’ values.