Lattice-structured, microperforated panel with high perforation ratio for broadband sound absorber

Abstract

A microperforated panel (MPP), in the form of a distributed Helmholtz resonator, has submillimeter holes on a planar panel, inducing high sound absorption at a single peak within a narrow frequency range. However, broadening the bandwidth and reducing the volume of an MPP to the subwavelength scale is necessary to expand its application in room acoustics, transport, and aerospace engineering industries. In this work, we propose a lattice-structured MPP (LMPP) with a smaller perforation size and higher perforation ratio, which demonstrates high absorption performance at the subwavelength scale. By tuning the material flow rate in a fused deposition modeling-type three-dimensional printing process, LMPPs were easily fabricated with a small perforation of 0.05- 0.4 mm in square configuration and a perforation ratio range of 0.65- 41.50 %. The fabricated LMPP showed a high sound absorption coefficient (alpha> 0.9) with a wider bandwidth at mid- and high-frequencies (800-4,000 Hz) owing to the lower resistance and better impedance matching on the panel surfaces. Furthermore, inhomogeneous LMPPs (iLMPPs) were fabricated by arranging LMPPs with different perforation sizes in parallel. Owing to the overlapping effect of the resonance peaks of each sub-LMPP, iLMPP exhibited broad absorption characteristic of the effective absorption bandwidth over 4,635 Hz at the first peak frequency of 2,234 Hz, resulting in an overall subwavelength (<lambda/10) thickness of 11 mm. The additively fabricated LMPPs exhibited strong advantages with easy tuning of the perforation geometry or distribution, which could be effective for various applications requiring smaller volumes or complex geometries.