On the modelling of microslit panel absorbers

Microslit panel absorbers are panels where the microperforations are slits instead of circular holes. Specific models have been proposed for such absorbers that provide the input impedance as a function of four non-acoustical parameters, namely d, the width of the slits, t, the thickness of the panel, phi, the perforation ratio, and D, the air cavity thickness. But, the impedance model of classical microperforated panels, that is, the model proposed for circular holes, can also be applied, taking d as the corresponding hydraulic diameter. Both models are compared in this paper with the measured curves for microslit samples produced by laser machining and 3D printing. Although none of the absorption curves supplied by both models fit closely the measured absorption curves for the samples, the ones given by the microperforated model approaches better than those afforded by the microslit model. Therefore, Simulated Annealing is applied to estimate the non-acoustical parameters of both models that minimise the difference between the measured and predicted curves. Again, the microperforated model provides more plausible non-acoustical parameters. (C) 2019 Elsevier Ltd. All rights reserved.