Study of a New Highly Absorptive Acoustic Element

The highly absorptive acoustic element studied in this paper is constituted by two mating plates provided with slots and a number of micro-channels engraved on the contact surface. This fibre-less element has been first presented in a previous work, with the name of micro-grooved element (MGE), as a potential substitute of the well-known micro-perforated element (MPE) (Auriemma et al. in SAE Int J Mater Manuf 6(3), 2013). Compared to MPE, it offered advantages in terms of cost-effectiveness of the production process, but similar acoustic behaviour. In this paper, MGEs with improved design are presented. The new geometry of the outer layers results in inner micro-channels with smaller overall dimensions, while still keeping adequate porosity. As a result, the acoustic behaviour is enhanced and the sound absorption of traditional MPEs is finally overcome. The transfer impedances of several MGE and MPE samples are measured, modelled and compared. The impedance end corrections are extrapolated with a completely experimental procedure and the behaviour in nonlinear regime is studied and described by means of a semi-empirical formulation.