DEVELOPMENT OF MICRO-PERFORATED PANELS (MPP) AS WIDEBAND SOUND ABSORBERS: COMBINATION OF MULTI-LAYERED PANELS AND INHOMOGENEOUS PERFORATIONS

• Main Author: Maulana Makmoen, Kinan
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/54819
• Institution: Institut Teknologi Bandung

Micro-perforated panels (MPP) were first formulated by Maa to improve on the shortcomings of conventional sound absorbers as the result of fibrous material usage. However, their Helholtz-resonator-based absorption mechanism provides only a narrow bandwidth near the resonancy frequency of the MPP. The series (multi-layered) and parallel (inhomogeneous perforations) configurations are able to widen the bandwidth, but risk using excessive system width or increasingly complex structure. MPP with perforation diameters less than 0.1 mm also produce a wide absorption bandwidth, but requires complicated manufacturing. Therefore, a parametric study is done to examine the benefits of series and parallel configurations, as well as usage of diameters up to 0,1 mm small, to build an MPP system that combines series and parallel configurations, aiming to benefit from each configuration while mitigating their shortcomings. Based on Maa’s mathematical model of the MPP and its equivalent electric circuit, 2 combined MPP models using 3 and 4 sub-MPPs are constructed. Then, further analysis is conducted on the comparison between 2 simulation models: (1) the analytic model generated from MATLAB, and; (2) the numeric, finite element method (FEM) model that simulates impedance tube testing conditions. For all models, the simulation results exhibit an adequate match with the predicted absorption profiles. Both models are capable of widening the absorption bandwidth to the range of 3 to 7 kHz, with peak absorption coefficients ranging from 0.8 to 0.99. They elso exhibit better performance than series and parallel systems, i.e. smaller total width and simpler physical structure. Nonetheless, both combined models also show that by maintaining the total system width below 50 mm, a trade-off occurs between having a wide half-absorption bandwidth (wider than 4 kHz) and a low-frequency bandwidth bound (below 500 Hz). Therefore, the aim of the combined MPP system should be defined.