François-Xavier Bécot

MATELYS - Research Lab

When designing passive sound-attenuation structures, one of the challenging problems that arise is optimally distributing acoustic porous materials within a design region so as to maximise sound absorption while minimising material usage. To identify efficient optimisation strategies for this multi-objective problem, several gradient, non-gradient,...

The paper shows that acoustic materials with double porosity can be 3D printed with the appropriate design of the main pore network and the contrasted micro-porous skeleton. The microporous structure is obtained through the use of appropriate additive manufacturing (AM) technology, raw material, and process parameters. The essential properties of t...

We introduce a novel heterogeneous multi‐scale method for the frequency response analysis of waves propagating in porous domains with a complex micro‐structure. In this, the domain is decomposed onto polygonal coarse elements each clustering its local micro‐structure. The micro‐structure is resolved using the virtual element method hence providing...

This paper shows that specific additive manufacturing (AM) technology can be used to produce double-porosity acoustic materials where main pore networks are designed and a useful type of microporosity is obtained as a side effect of the 3D printing process. Here, the designed main pore network is in the form of annular pores set around the axis of...

The paper shows that acoustic materials with double porosity can be 3D printed with the appropriate design of the main pore network and the contrasted microporous skeleton. The microporous structure is obtained through the use of appropriate additive manufacturing (AM) technology, raw material, and process parameters. The essential properties of th...

At first glance, it seems that modern, inexpensive additive manufacturing (AM) technologies can be used to produce innovative, efficient acoustic materials with tailored pore morphology. However, on closer inspection, it becomes rather obvious that for now this is only possible for specific solutions, such as relatively thin, but narrow-band sound...

Engineered wood constructions and timber buildings are rapidly developing, while the numerical techniques usable for their sound insulation properties are various and often still under development. This research constitutes a first step towards the reliability determination of building acoustics simulations on timber-based elements. A small scale r...

Meta-materials have been a subject of great interest in the field of acoustic materials for several years. The term « meta » is used to emphasize that at least one non-conventional phenomenon is used. These meta-materials could also be called multiple dynamic materials. A large number of works are published every year in this field and it may be di...

When designing sound packages, often fully filling the available space with acoustic materials is not the most absorbing solution. Better solutions can be obtained by creating cavities of air pockets, but determining the most optimal shape and topology that maximises sound absorption is a computationally challenging task. Many recent topology optim...

Acoustic wave propagation in porous composites is investigated in this paper. The two-scale asymptotic homogenisation method is used to obtain the macroscopic description of sound propagation in such composites. The developed theory is both exemplified by introducing analytical models for the effective acoustical properties of porous composites wit...

Sound absorption of polydisperse heterogeneous porous composites is investigated in this paper. The wave equation in polydisperse heterogeneous porous composites is upscaled by using the two-scale method of homogenization, which allows the material to be modeled as an equivalent fluid with atypical effective parameters. This upscaled model is numer...

Sound absorption of polydisperse heterogeneous porous composites is investigated in this paper. The wave equation in polydisperse heterogeneous porous composites is upscaled by using the two-scale method of homogenisation, which allows the material to be modeled as an equivalent fluid with atypical effective parameters. This upscaled model is numer...

This paper investigates sound propagation in polydisperse heterogeneous porous composites. The two-scale asymptotic method of homogenization is used to obtain a macroscopic description of the propagation of sound in such composites. The upscaled equations demonstrate that the studied composites can be modeled as equivalent fluids with complex-value...

This work presents a prediction model for rolling noise in multi-story buildings, such as that generated by a rolling delivery trolley. Until now, mechanical excitation in multi-story buildings has been limited to impact sources such as the tapping machine. Rolling noise models have been limited to outdoor sources such as trains and automotive vehi...

This work presents a prediction model for rolling noise in multi-story buildings, such as that generated by a rolling delivery trolley. Until now, mechanical excitation in multi-story buildings has been limited to impact sources such as the tapping machine. Rolling noise models have been limited to outdoor sources such as trains and automotive vehi...

Mutli-layered structures (such as sandwich panels) are commonly used in engineering applications for improved sound comfort and noise reduction. Finite Element modelling of these layered structures would often results in increased total number of degrees of freedom which would lead to high computation time. An alternative to the full modelling of m...

This work presents a prediction model for rolling noise in multi-story buildings, such as that generated by a rolling delivery trolley. Until now, mechanical excitation in multi-story buildings has been limited to impact sources such as the tapping machine. Rolling noise models have been limited to outdoor sources such as trains and automotive vehi...

We introduce a novel heterogeneous multi-scale method for the consolidation analysis of two-dimensional porous domains with a complex micro-structure. A two-scale strategy is implemented wherein an arbitrary polygonal domain can be discretised into clusters of polygonal elements, each with its own set of fine scale discretization. The method harnes...

The use of foam materials as a means of improving the sound absorption and transmission properties of structures, especially at low frequencies, has been receiving considerable attention over the past years. Unfortunately , the underlying complex material domain that may include solid inclusions, renders numerical simulation using the standard FEM...

Structural topology optimisation techniques are increasingly being applied to acoustic materials. Most acoustic topology optimisation applications use the solid-isotropic-material-with-penalization (SIMP) approach which is a derivative-based method. In this work, we study the use of covariance-matrix-adaptation-evolution-strategy (CMA-ES) considere...

The optimization of multilayered-sound-packaging is a challenging task which involves searching the best/op-timal settings for a number of acoustic parameters. The search space size becomes too large to handle by brute force, as the number of those parameters increases. In this study, we apply metaheuristics to configure multi-layered porous materi...

When analyzing the effect of damping factor of a simple plate subjected to an airborne excitation, the effect of damping is well known. Its effect is mainly observed around the critical frequency. This observation is no longer valid when looking at other types of excitations (turbulent boundary layer, point force, rainfall, tapping machine ...). Th...

In vehicle tire/road contact modeling, dynamic models are typically used which incorporate the vehicle’s suspension in their estimation: thus relying on a known stiffness to determine the movement of the wheel in response to roughness excitation. For the case of a wheeled device rolling on a floor (such as a delivery trolley moving merchandise arou...

We introduce a novel heterogeneous multiscale method for the elastic analysis of two‐dimensional domains with a complex micro‐structure. To this end, the multiscale finite element method is revisited and originally upgraded by introducing virtual element discretizations at the micro‐scale hence allowing for generalised polygonal and non‐convex elem...

In vehicle tyre/road contact modelling, dynamic models are typically used which incorporate the vehicle's suspension in their estimation: thus relying on a known stiffness to determine the movement of the wheel in response to roughness excitation. For the case of a wheeled device rolling on a floor (such as a delivery trolley moving merchandise ins...

New buildings in urban areas are divided into commercial and habitable areas. Commercial shops typically exist on the ground floors, with private residencies on the upper floors. This use has revealed critical disturbances due to the noise generated by rolling delivery carts when the buildings are mainly occupied (e.g. early in the morning). These...

There is a considerable number of research publications on the acoustical properties of porous media with an elastic frame. A simple search through the Web of Science™ (last accessed 21 March 2018) suggests that there are at least 819 publications which deal with the acoustics of poroelastic media. A majority of these researches require accurate kn...

We measured the acoustic absorption, in the 0.5–6 kHz frequency range, of polyurethane foams with mean pore diameters between 0.6 and 3.2 mm. Two types of foams were investigated: classical open-cell ones versus membrane foams, in which thin polyurethane membranes were preserved during solidification. Interestingly, the latter presented better abso...

New buildings in urban areas are divided in commercial and living surfaces. This usage has revealed critical disturbances due to the noise of the trolleys delivering at time where the buildings are mostly occupied, e.g., early times in the morning. Rolling trolleys indeed generate low frequency vibrations (below 100 Hz) which propagate easily in th...

Acoustical facings (including micro perforated panels—MPP—woven and non-woven textiles, screens..) which can be used in association with porous materials, have been widely studied. A large number of models are described in the literature. This work presents a comparison of these models discussing particularly the expression of the corrections relat...

There is a considerable number of research publications on the characterization of porous media that is carried out in accordance with ISO 10534-2 (International Standards Organization, Geneva, Switzerland, 2001) and/or ISO 9053 (International Standards Organization, Geneva, Switzerland, 1991). According to the Web of ScienceTM (last accessed 22 Se...

Acoustical porous materials are commonly used to reduce the noise in the presence of flow. In such applications, it is essential to control how these materials may alter the flow and may regenerate noise. The purpose of this work is to show different ways to take into account the porous materials in Computational Fluid Dynamics (CFD) simulations an...

Based on a modified equivalent fluid model, the present work proposes a composite model which analytically includes the shape of the inclusions, whether they are porous or not. This model enables to describe the acoustic behavior of a large range of media from perforated plates to arbitrarily shaped porous composites including configurations of por...

Among porous materials, food products represent a large range of micro-structures usually studied in acoustics. These media may indeed include open or closed cell foams, fibrous materials, granular materials, functionally graded materials, porous media with poro-elastic inclusion etc. Therefore, they represent major modeling and experimental challe...

When analyzing the effect of damping factor of a simple plate subjected to airborne excitation, the effect of damping is well known. Its effect is mainly observed around the critical frequency. This observation is no longer valid when looking at other types of excitations (turbulent boundary layer, the point load, rainfall, tapping machine ...). Th...

The work proposed here deals with theory and experiment on the acoustics of gas saturated rigid porous media with inner resonance effects. First, we investigate the physics of porous media in which inner resonance phenomena occur. Then, through the homogenization method the macroscopic descriptions of (i) porous media constituted by a packing of He...

This paper presents an alternative formulation of Biot’s theory to account for the elastic frame effects in a porous medium in which the acoustical properties of the fluid phase are predicted with an equivalent fluid model. This approach was originally developed for a double porosity medium. In this paper, the alternative formulation is applied to...

This work aims at linking the in-situ measured surface properties of a given single-layer or multi-layer system to its intrinsic characteristics. The methods for measuring in-situ the surface properties, which are numerous and were proved to be robust, provide however only limited information about the material dissipation mechanisms. For some mate...

Semi-phenomenological models have been widely used since the 1990's for modeling visco-thermal dissipations of acoustical energy through porous media. These dissipations are taken into account by two complex frequency-dependent functions (the dynamic density ρeq (ω) and the dynamic bulk modulus Keq (ω)), which are analytically derived from macrosco...

In this paper, a model for sound propagation in double porosity materials with elastic frame is proposed. The main originality of this paper is to develop a model which is suitable for sound absorbing materials. The original idea is to replace the fluid-phase related properties of a single porosity material in Biot transverse isotropic equations wi...

Perforated facings (including Micro Perforated Panels) or perforated ceiling tiles have been widely studied since the fundamental work by Uno Ingard. This work specially focus on flow modifications in the vicinity of the perforations leading to modifications of the reactance of the panel. This communication is a synthesis study of pioneer and recen...

Impedance tube is widely used to characterize acoustical materials, but it is restricted to frequencies corresponding to plane wave mode propagation. Broadband measurements require testing samples within tubes of different cross-sections: the smaller the diameter the higher the maximum frequency allowed. This is a critical issue for materials or mu...

This article explores the applicability of numerical homogenization techniques for analyzing transport properties in real foam samples, mostly open-cell, to understand long-wavelength acoustics of rigid-frame air-saturated porous media on the basis of microstructural parameters. Experimental characterization of porosity and permeability of real foa...

Ever demanding weight reduction criteria leads to high demands on the vibro-acoustic modeling tool accuracy. These demands face the difficulty of accessibility to the various required parameters and the selection and relevance of the dissipative models. Especially targeted systems are acoustic perforated membrane/fabrics and multi-scale materials,...

This paper examines the potential of using composite porous materials to design robust noise control packages. Composite porous are meso-perforated porous materials in which perforations are filled with another porous material. The work presented here shows that the association of two carefully selected materi-als could lead to interesting combined...

An experimental method to estimate the acoustical parameters of perforated facings used for noise control applications is proposed. These perforating facings (also called screens) can be woven or non-woven fabrics or even micro-perforated plates (MPP). Following the work by Atalla and Sgard [J. Sound Vib. 303, 195-208 (2007)], the perforated facing...

This paper is concerned with the analytical modeling of the acoustic properties of materials which could show interesting combined performances of sound absorption and sound insulation. These materials, made from porous materials having porous inclusions, are called composite porous materials by analogy with standard composite materials composed by...

Recycling polymers is attractive to reduce the amount of industrial waste and to limit the traditional dependence on virgin petro-chemical products. In order to produce competitive acoustic products it is important to understand the relationships between the material microstructure and the manufac-turing process parameters. This paper presents resu...

The combined mechanical and acoustic properties of auxetic (negative Poisson's ratio) foams are described both from a numerical and experimental point of view. Samples of open cell PU-PE foams with negative Poisson's ratio are produced using a dedicated manufacturing process, and subjected to tensile quasi static and cyclic loading, as well as soun...

This paper presents recent developments in the field of micro-acoustics of porous media. The fundamental idea of the proposed approach is that it is possible to assess porous microstructure and acoustical properties from the three-dimensional implementation of micro-acoustics based scaling relations on porous materials. We illustrate this approach...

During lift-off, space launchers are submitted to high-level of acoustic loads, which may damage sensitive equipments. A special acoustic absorber has been previously integrated inside the fairing of space launchers to protect the payload. A new research project has been launched to develop a low cost fairing acoustic protection system using optimi...

The Sound Transmission Loss (STL) of Autoclaved Aerated Concrete (AAC) materials computed with an isotropic elastic model is usually underestimated by 5 to 8dB in the low frequency range (50-400 Hz). A better approximation of AAC STL can be achieved by using a model that also takes into account the porous characteristics of the material. By using t...

This paper addresses the FEM prediction of the vibro-acoustic behavior of an enclosure surrounding a sound source, which is treated using multiscale poroelastic materials.The enclosure consists of a five rigid wall cavity coupled to a flexible metal plate. The plate, the enclosed air and the acoustical treatment are modeled using a finite element m...

Non planar acoustic materials may be used in building and environmental acoustics to achieve a significant absorption at low frequencies. Examples of these materials are anechoic wedges or advanced design noise barriers. The shape of these materials is mainly based on empirical knowledge because a fine numerical modeling (e.g. FEM, BEM) requires la...

Despite the numerical advances, predicting the sound field in anechoic rooms is still challenging because it requires a fine modeling of the wall surface, acoustic properties and geometry, and the computation of the room sound field. It is proposed here to compare two innovative approaches to predict the performance of anechoic wedges, in particula...

This paper is devoted to the rigorous obtention of the energy balance in porous materials. The wave propagation in the porous media is described by Biot-Allard's {u,U} and {u,P} formulations. The paper derives the expressions for stored kinetic and strain energies together with dissipated energies. It is shown that, in the case of mixed formulation...