Macro- and micro-structure designs for porous sound absorbers

Attenborough, Keith

doi:10.1016/j.apacoust.2018.10.018

Cited by 17 publications

(13 citation statements)

References 19 publications

(58 reference statements)

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“…Although standard porous materials, like open cell foams or fibrous material, are still very competitive for acoustic treatments, their efficiency is limited in the low frequency range by their thickness [1]. If their microstructure can be optimized to meet specific requirements [2][3][4], their manufacturing is now achievable using 3D printing techniques for experimental validation at the scale of a laboratory. Indeed, the development of Additive Manufacturing (AM) technologies [5][6][7][8][9][10][11][12] gives new possibilities to manufacture and test optimised micro-geometries.…”

Section: Introductionmentioning

confidence: 99%

Reproducibility of sound-absorbing periodic porous materials using additive manufacturing technologies: Round robin study

Zieliński

Opiela

Pawłowski

et al. 2020

Additive Manufacturing

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The purpose of this work is to check if additive manufacturing technologies are suitable for reproducing porous samples designed for sound absorption. The work is an inter-laboratory test, in which the production of samples and their acoustic measurements are carried out independently by different laboratories, sharing only the same geometry codes describing agreed periodic cellular designs. Different additive manufacturing technologies and equipment are used to make samples. Although most of the results obtained from measurements performed on samples with the same cellular design are very close, it is shown that some discrepancies are due to shape and surface imperfections, or microporosity, induced by the manufacturing process. The proposed periodic cellular designs can be easily reproduced and are suitable for further benchmarking of additive manufacturing techniques for rapid prototyping of acoustic materials and metamaterials.

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Section: Introductionmentioning

confidence: 99%

Reproducibility of sound-absorbing periodic porous materials using additive manufacturing technologies: Round robin study

Zieliński

Opiela

Pawłowski

et al. 2020

Additive Manufacturing

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“…The expressions for bulk, Ω B , and surface, Ω S , porosities of the horizontal-and vertical-wall labyrinth structures in Figure 1 are given in Equations ( 5) to (8),…”

Section: Labyrinthine Slits Formed By Walls Parallel and Normal To The Layer Surfacementioning

confidence: 99%

“…The broken line in Figure 6 indicates the assumed zigzag approximation to the streamline path. The tortuosity of this labyrinthine architecture, , is the product of that resulting from the zig-zag approximation of the streamline path and that due to the changes in cross The tortuosity of this labyrinthine architecture, T AWZ , is the product of that resulting from the zig-zag approximation of the streamline path and that due to the changes in cross section [8] which is the second factor in Equation (15). Similarly, the tortuosity, T AWC , with the slit centre line path approximation is given by Equation (16).…”

Section: Alternating-width Vertical-wall Labyrinthine Slit Perforation In a Porous Matrixmentioning

confidence: 99%

“…Sci. 2021, 11, x FOR PEER REVIEW 7 of 10 section [8] which is the second factor in Equation (15). Similarly, the tortuosity, , with the slit centre line path approximation is given by Equation (16).…”

Section: Alternating-width Vertical-wall Labyrinthine Slit Perforation In a Porous Matrixmentioning

confidence: 99%

“…Then the dual-porosity theory [6,7] is used to predict the results of incorporating labyrinthine slits in a matrix of a rigid-porous material with high flow resistivity. The influence of additional tortuosity due to changes in labyrinthine slit cross section [8] is considered. Useful narrowband low-frequency absorption is predicted to result from pressure diffusion and tortuosity effects.…”

Section: Introductionmentioning

confidence: 99%

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Analytical Approximations for Sub Wavelength Sound Absorption by Porous Layers with Labyrinthine Slit Perforations

Attenborough

2021

Applied Sciences

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Analytical approximations for the acoustical properties of a rigid-porous matrix perforated by labyrinthine slits are developed using classical theories for sound propagation in tortuous slits and for sound absorption by double porosity materials. Predictions of enhanced low-frequency absorption result from a combination of pressure diffusion and labyrinth tortuosity if there is a high permeability contrast between the matrix and the labyrinthine slit. Additional insight into the predicted influence of the properties of the porous matrix is gained by considering the matrix porosity to be provided by inclined micro-slits. Extra tortuosity can be introduced by alternating the width of the labyrinthine slit. An alternating-width vertical-wall labyrinth perforation is predicted to lead to low-frequency absorption peaks in a relatively low-flow-resistivity and low-porosity matrix. Example predictions, even when using underestimates of labyrinth tortuosity, demonstrate the potential of labyrinthine slit perforations for achieving narrowband deep sub wavelength absorption peaks from thin hard-backed porous layers.

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Custom‐Built Graphene Acoustic‐Absorbing Aerogel for Audio Signal Recognition

Yang

Lupi

et al. 2021

Adv Materials Inter

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Porous acoustic‐absorbing materials currently used to solve noise pollution mainly include polyurethane composite materials and porous fibers which are dedicated to achieving good noise reduction effects in a wide frequency range. Nevertheless, traditional porous acoustic‐absorbing materials face irreparable defects as required by the multifunction and high energy efficiency. The reason is nothing more than the internal microstructure of conventional acoustic‐absorbing materials is difficult to be precisely controlled by macroscopic operations, resulting in poor mass transfer capability and low energy conversion efficiency. In this work, by customized design of controlled mechanical foaming and atmospheric drying technique, a custom‐built graphene aerogel (cGA) as acoustic‐absorbing material with an acoustic absorption coefficient approaching 100% is prepared, which can efficiently absorb noise at an assigned frequency (2000–6000 Hz range) according to individual needs. Through simple stacking, cGAs expand from single‐frequency absorption to multi‐frequency high‐efficiency absorption. What is more significant is that a single aerogel has electrical signal responses of different intensities to sounds of different frequencies, which allows to build the aerogel into an acoustic detector to convert noise signals into electrical signals and realize the goal of sound fingerprint detection.

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Macro- and micro-structure designs for porous sound absorbers

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Cited by 17 publications

References 19 publications

Reproducibility of sound-absorbing periodic porous materials using additive manufacturing technologies: Round robin study

Reproducibility of sound-absorbing periodic porous materials using additive manufacturing technologies: Round robin study

Analytical Approximations for Sub Wavelength Sound Absorption by Porous Layers with Labyrinthine Slit Perforations

Custom‐Built Graphene Acoustic‐Absorbing Aerogel for Audio Signal Recognition

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