Sound absorption of plates with micro-slits backed with air cavities: analytical estimations, numerical calculations and experimental validations

This work discusses many practical and some theoretical aspects concerning modelling and design of plates with micro-slits, involving multi-scale calculations based on microstructure. To this end, useful mathematical reductions are demonstrated, and numerical computations are compared with possible analytical estimations. The numerical and analytical approaches are used to calculate the transport parameters for complex micro-perforated (micro-slotted) plates, which allow to determine the effective properties of the equivalent fluid, so that at the macro-scale level the plate can be treated as a specific layer of acoustic fluid. In that way, the sound absorption of micro-slotted plates backed with air cavities can be determined by solving a multi-layer system of Helmholtz equations. Two such examples are presented in the paper and validated experimentally. The first plate has narrow slits precisely cut out using a traditional technique, while the second plate – with an original micro-perforated pattern – is 3D-printed.status: publishe