Rapid additive manufacturing of optimized anisotropic metaporous surfaces for broadband absorption

Abstract

Porous materials and metamaterials play a key role in sound absorbing and insulation solutions in acoustics. With the growing interest in additive manufacturing techniques, recent work has focused on the printing of porous and resonant structures for acoustic purposes. Usual metaporous surfaces/interfaces are generally built by periodically inserting resonant elements in an existing porous layer. This complex manufacturing process can be significantly simplified by using additive manufacturing techniques, which also eases the design and optimisation of the metaporous surface.In this work, the acoustic properties of the metaporous surface are controlled by simple geometric parameters defining both the anisotropic porous layer and the shapes of the resonators. Hence, we focus on optimising split-ring resonators embedded in a micro-treillis porous layer, which are built in a single part using additive manufacturing techniques. A finite-element method together with the Bloch wave decomposition provides a numerical model used to predict the reflection and absorption coefficients under normal incidence. The geometric parameters of the anisotropic metaporous surface are then optimised by non-linear minimisation techniques to maximise acoustic absorption. An optimal metaporous surface is 3D printed by fused-deposition modeling and its acoustic properties are measured in an impedance tube. The measurements are in good agreement with the predicted optimal broadband absorption coefficient. This work demonstrates the benefits of additive manufacturing for designing metaporous acoustic surfaces.

Extremely tortuous sound absorbers with labyrinthine channels in non-porous and microporous solid skeletons

“…In spite of many limitations, additive manufacturing technologies [34] are widely used in recent times to develop and prototype new acoustic materials [35][36][37][38][39][40]. For the specific purposes of this study, the panel samples were additively manufactured from two different raw materials in two technologies: (i) Stereolithography (SLA), a.k.a.…”

Perfect, broadband, and sub-wavelength absorption with asymmetric absorbers: Realization for duct acoustics with 3D printed porous resonators

“…In practice, it is used to differentiate conventional porous treatments having a weak sub-wavelength behavior, i.e., that cannot reach perfect absorption at normal incidence with h λ/4, from other types of resonator based structures or resonant structures having a strong sub-wavelength behavior, such as treatments based on HRs. Treatments made of porous materials can also achieve sub-wavelength absorption, for instance by incorporating resonant inclusions [25,26,27], optimizing a gradient of properties through their thickness [28,29,30] or folding their structure [31,32,33].…”

Enhanced Low-Frequency Sound Absorption of a Porous Layer Mosaicked with Perforated Resonator

“…It was demonstrated that the enhancement of sound absorption at frequencies lower than a quarter wavelength results from the Helmholtz resonance in the viscous regime and the trapped modes in the inertial regime. In addition, with the maturity of rapid additive manufacturing technol-ogy, the optimized graded porous materials [34,35], folded metaporous material [36], and anisotropic metaporous surfaces [37] have been fabricated using 3D printing for broadband sound absorption.…”