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

Andrew Mckay,Jack Killeen,Gareth J Bennett,Ian Davis

doi:10.1038/s41598-020-73933-0

Andrew Mckay, Jack Killeen + Show 2 more

Open Access

https://doi.org/10.1038/s41598-020-73933-0

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Journal: Scientific Reports	Publication Date: Oct 21, 2020
Citations: 18	License type: open-access

Affiliation: Trinity College Dublin, Nokia (Ireland)

Abstract

The attenuation of low-frequency broadband noise in a light, small form-factor is an intractable challenge. In this paper, a new technology is presented which employs the highly efficient visco-thermal loss mechanism of a micro-perforated 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 sub-wavelength thicknesses. The technology is compared to other absorbers to be found in the literature and the SeMSA outperforms them all in either the 20–1000 Hz or 20–1200 Hz range for depths of up to 120 mm. This was verified through analytical, finite element and experimental analyses.

Highlights

The attenuation of low-frequency broadband noise in a light, small form-factor is an intractable challenge
The cell is circular to match the internal diameter of the impedance tube but it is machined from a block of brass to ensure no transmission through the Segmented Membrane Sound Absorber (SeMSA) walls and so that it may be secured to the end of the tube
The decorated membrane is made from a sheet of latex rubber τm = 0.18 mm thick carefully glued down to the edges of the SeMSA cell including along the top of the micro-perforated plate (MPP)

Summary

Introduction

The attenuation of low-frequency broadband noise in a light, small form-factor is an intractable challenge. The exercise shows that the current technology, through an optimisation routine of the equivalent circuit model, results in the best performing sound-absorbing solution in the 20–1200 Hz range for a wide range of technology depths.

Results

Conclusion