Porous materials for sound absorption

Sound absorption behavior of flexible polyurethane foams with distinct cellular structures

Influence of filler surface characteristics on morphological, physical, acoustic properties of polyurethane composite foams filled with inorganic fillers

The work describes the mechanical performance of a metal rubber particles (MRP) damper design based on an auxetic (negative Poisson’s ratio) cellular configuration. The auxetic damper configuration is constituted by an anti-tetrachiral honeycomb, where the cylinders are filled with the MRP material. The MRP samples have been subjected to quasi-static loading to measure the stiffness and loss factor from the static hysteresis curve. A parametric experimental analysis has been carried out to investigate the effect of relative density and filling percentage on the static performance of the MRP, and to identify design guidelines for best use of MRP devices. An experimental assessment of the integrated auxetic-MRP damper concept has been provided through static and dynamic force response techniques. (Some figures may appear in colour only in the online journal)

https://iopscience.iop.org/article/10.1088/0964-1726/22/8/084012/pdf

A nonlinear auxetic structural vibration damper with metal rubber particles

Vibration and noise control using shunted piezoelectric transducers: A review

In this article, rice hull (RH) was used in the moulding of polyurethane (PU) foam system. The article analyzed the participation of RH in the chemical reaction of PU synthesis with Attenuated Total Reflection-Fourier Transform Infrared spectroscopy method. Besides, the influence of RH on the formation of pore structure along with the acoustic performance such as sound impedance rate, acoustic reflection factor, sound absorption coefficient, and transmission loss of the products were studied with the Transfer Function Method. The results indicated that RH significantly influenced the uniformity of pore diameter in PU foam. As the content of RH increased, the sound absorption peak shifted toward lower frequency region. And the sound absorption coefficients increased till a threshold value of RH content. POLYM. COMPOS., 34:1847–1855, 2013. V C 2013 Society of Plastics Engineers

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Influences of rice hull in polyurethane foam on its sound absorption characteristics

https://acoustique.ec-lyon.fr/publi/wang_cs14.pdf

Sound absorption of a new bionic multi-layer absorber

https://northumbria-test.eprints-hosting.org/id/document/272645

Small perforations in corrugated sandwich panel significantly enhance low frequency sound absorption and transmission loss

Identification of effective sandwich structural properties via an inverse wave approach

This paper deals with the design of periodic piezoelectric structures for broadband vibration control. By shunting identical negative capacitances to the periodically distributed piezoelectric patches, a wide and continuous band gap is created so as to cover the frequency range of interest. This way the modal density of the structure is reduced and the modal shapes are localized at the boundaries. A large proportion of the energy can then be removed or dissipated by a small number of dampers or energy harvesters integrated within the negative capacitance circuits. A design process is proposed to achieve the wide band gap. The overall amount of piezoelectric materials is constrained in order to keep mass of structures low. The wave electromechanical coupling factor is proposed and used as a criterion. This allows to reach the largest width of the band gap by using a stable value of negative capacitance. The control of multiple high-order modes of a cantilever beam is considered as an example. The vibration reduction performance of the designed piezoelectric structures is presented and the influences of band gap resonance, resistor and the boundary condition are discussed. The proposed approach is fully based on wave characteristics and it does not rely on any modal information. It is therefore promising for applications at mid- and high frequencies where the access to the exact modal information is difficult.

https://iopscience.iop.org/article/10.1088/0964-1726/25/5/055032/pdf

Olivier Bareille

Papers

Influences of rice hull in polyurethane foam on its sound absorption characteristics

Sound absorption of a new bionic multi-layer absorber

Small perforations in corrugated sandwich panel significantly enhance low frequency sound absorption and transmission loss

Identification of effective sandwich structural properties via an inverse wave approach

A wave-based design of semi-active piezoelectric composites for broadband vibration control