SeMSA: a compact super absorber optimised for broadband, low-frequency noise attenuation

The attenuation of low-frequency broadband noise in a light, small formfactor is an intractable challenge. In this paper, a new technology is presented which employs the highly efficient visco-thermal loss mechanism of a microperforated plate (MPP) and successfully lowers its frequency response by combining it with decorated membrane resonators (DMR). Absorption comes from the membranes but primarily from the MPP, as the motion of the two membranes causes a pressure differential across the MPP creating airflow through the perforations. This combination of DMR and MPP has led to the Segmented Membrane Sound Absorber (SeMSA) design which is extremely effective at low frequency broadband sound absorption and which can achieve this at deep subwavelength thicknesses. The technology is compared to other absorbers to be found in the literature and the analytical model, the finite element model and the experimental results of the SeMSA outperform them all in the 20 Hz - 1200Hz range for depths of up to 120 mm.