Fabien Chevillotte

• MSc
• Manager at Matelys - Research Lab

Understanding and predicting the vibro-acoustic behavior of acoustical porous materials (like foams, synthetic or natural fibers, metamaterials...) requires to determine the parameters of their solid and their fluid phases. This work presents an non-exhaustive overview of the methods commonly used to assess the visco-elastic and acoustic parameters...

Two main classes of characterization methods are usually employed for acoustic parameters of porous media, namely the analytical inversion method or the numerical fitting procedure. While analytical inverse methods suffer from a high sensivity to the operator, the numerical fitting methods can lead to non physical sets of parameters. The fitting pr...

Multilayer systems are widely used in industry for their performances as compared with homogeneous materials. The layers are usually glued together but the bonding may be imperfect (air bubble, detachment). The interfaces are generally modeled as sliding or bonded. These two behaviors can be significantly different and the actual behavior is genera...

Porous treatments are more and more employed in presence of flow as passive noise control means to mitigate the generated noise. They are generally designed according to their acoustic dissipation properties under no-flow conditions. Nevertheless, in-flow porous treatments can alter the aerodynamic properties, modify the main acoustic source itself...

The air filters installed in ventilation systems are designed for collecting dust and particles. These filters usually consist in folded paper or textile, arranged either as a flat slab or in a V-shape frame. Some of them may also contain activated carbon in order to remove molecular compounds. Experimental results show that they can significantly...

Predicting the vibroacoustic behaviour of structures in contact with water and at high frequencies can be a complex task due to the fluid-structure interaction. Computation time increases with frequency and the complexity of the structure. Being able to predict the sound radiated by a naval vehicle in contact with water could help in improving pass...

The computation of the diffuse field response of multilayered homogeneous structures leads to integrals which should be computed efficiently. This is all the more true as the frequency increases, since the integrand has localized peaks. The objective of this communication is to propose an adaptive integration scheme that aims to limit the number 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 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...

Condensed models act as useful tools to reduce the computational time in the finite element simulations by describing the dynamic behaviour of the multi-layer structure with only one equivalent homogeneous layer. Many condensed plate models in the literature assume constant velocity through the thickness which allows only anti-symmetric motions lik...

We develop a novel Virtual Element Method (VEM) to resolve the mixed Biot displacement pressure formulation governing wave propagation in porous media. Within this setting, the weak form of the governing equations is discretized using implicitly defined canonical basis functions and the resulting integral forms are computed using appropriate polyno...

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...

The main goal of these industrial chapters is to help non-specialist engineers throughout the industry to take robust noise treatments optimization decisions without being obliged to become experts themselves. Another goal is also to help “low hanging fruit” technology transfers between various fields of acoustic industrial application domains, fro...

This chapter aims at presenting various building applications using porous materials. The role of porous materials and the relevant phenomena will be introduced for four typical applications, namely the acoustical correction, air-borne insulation, solid-borne insulation and ceiling applications. This chapter attempts to help the reader to identify...

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...

Condensed models are used to describe the dynamic behaviour of a multilayer structure by means of an equivalent homogeneous layer defined by intrinsic properties. Existing condensed models mainly describe the bending, membrane and shearing motions of the multilayer plate and neglect its dilatational motion. As a result, the transmission loss across...

This paper focuses on the analysis of dynamic pressure fluctuations in hydro-electric power plants. Pressure fluctuations are usually measured with remote sensors and the dynamic behaviour of the remote tubing line modifies the readings of dynamic pressure and thus introduces a bias. A method to characterize the remote tubing line and to correct th...

The tapping machine has long existed as the primary standard method for measuring the performance of floors in buildings in response to structure-borne noise. However, other sources of structure-borne noise exist. One of these is rolling noise: such as a trolley rolling across the floor in an indoor building environment. Because the sound profile o...

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...

Equivalent or condensed plate models are being used in various industries to reduce the computation time in finite element modelling. Out of the available equivalent plate models, the model developed by J.L.Guyader in 1978 exhibits high agreement with Lamb wave theory but it requires some time for implementation. Therefore, in this paper, a simple...

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...

Several vibro-acoustic models for either single wall or multi-layer constructions are based on classical plate and first order shear deformation theories. The equivalent or condensed plate models employ the thin plate model to extract the dynamic mechanical properties of the multi-layer system considering only flexural and shear motions for the str...

Equivalent plate models are commonly used in order to simulate multilayer system as one single layer. This kind of approach enables for instance to reduce the mesh size and thus the number of degrees of freedom in finite element models. Usual condensed model rely on thin plate theory and are obviously limited when considering thick multilayers. In...

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...

This work presents benchmark examples related to the modelling of sound absorbing porous media with rigid frame based on the periodic geometry of their microstructures. To this end, rigorous mathematical derivations are recalled to provide all necessary equations, useful relations, and formulas for the so-called direct multi-scale computations, as...

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...

Compressed porous materials (fibrous, felts, foams) are widely used in industry. The charaterization of macroscopic intrinsic properties (open porosity, airflow resistivity, tortuosity, viscous and thermal lengths, ...) enables to model a porous medium in various conditions (thicknesses, assembly with other layers, excitation) using the same set of...

Multilayer systems are widely used for sound transmission insulation and generally have mechanical links to ensure their strength and/or rigidity. Double leaf structures with mechanical links are commonly used in buildings or in transportations (railways, aeronautics, etc...). Several analytical models already enable to take into account both the a...

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...

The non-linear behavior of micro-perforated plates (MPP) under high sound pressure level (SPL) is studied at the microscopic scale using lattice Boltzmann method (LBM) in order to improve analytical models. Numerous analytical models can be found in the literature for modeling the linear behavior of micro-perforated plates. They mainly differ in th...

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...

This work discusses many practical and some theoretical aspects concerning modelling and design of plates with micro-slits, involving multi-scale calculations based on microstructure. To this end, useful mathematical reductions are demonstrated, and numerical computations are compared with possible analytical estimations. The numerical and analytic...

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...

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...

This work focuses on the length correction due to radiation effect of a duct discontinuity or at the surface of a perforated plate in the linear acoustic domain and at large wavelengths. Two results are obtained from the comparison of models used in the literature for different geometries of duct discontinuities or perforations. First, the mode-cou...

This work focuses on the length correction due to radiation effect of a duct discontinuity or at the surface of a perforated plate in the linear acoustic domain and at large wavelengths. Two results are obtained from the comparison of models used in the literature for different geometries of duct discontinuities or perforations. First, the mode-cou...

The purpose of this work is to systematically study the effect of the throat and the pore sizes on the sound absorbing properties of open-cell foams. The three-dimensional idealized unit cell used in this work enables to mimic the acoustical macro-behavior of a large class of cellular solid foams. This study is carried out for a normal incidence an...

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...

An outline is made of physical behaviour of water - filled large pipes. The fluid-wall coupling, the key factor governing the pipe dynamics, is discussed in some detail. Different circumferential pipe modes and the associated cut-on frequencies are addressed from a theoretical as well as practical point of view. Major attention is paid to the breat...

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...

An experimental validation is implemented for the measurement of a weak acoustic component within a turbulent wall pressure by an inverse problem of vibration. The turbulent flow is generated by a forward-facing step in a wind tunnel. In addition to the flow, an acoustic source with a low level excites the plate and plays the role of an additional...

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 acoustic pressure in the nearfield of a wall in a flow can be decomposed in different components: a first part is related to the vortices resulting from the perturbation of the flow by the presence of the wall, a second part is due to the acoustic waves generated by the parietal pressure fluctuations diffracted by the wall, and a third part is...

The acoustical macro-behavior of mineral open-cell foam samples is modeled from microstructure morphology using a three-dimensional idealized periodic unit-cell (3D-PUC). The 3D-PUC is based on a regular arrangement of spheres allowed to interpenetrate during the foaming process. Identification and sizing of the 3D-PUC is made from x-ray computed m...

The characterisation of the aeroacoustic wall pressure field generated by turbulent flow is a difficult task that often requires instrumented panels and huge facilities like wind tunnels. In situ and non-intrusive experiments are rather not possible. In addition, the pressure field is dominated by the aerodynamic component and the experimental dyna...

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...

A non-intrusive technique is presented for the detection of cavitation in a fluid filled pipe. This technique uses the coherence function between the signals from a pair of external sensors mounted on the pipe. In the non-cavitation conditions the phase structure between the signals is stable, giving high coherence. The presence of cavitation impai...

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...

Resistive screens, or perforated plates, are widely used upstream of porous materials. They can be used either for protection or decoration, or for acoustic properties enhancement. This study points out the role that a resistive layer can have upstream on a porous material. Based on numerical simulations, this work gives the guidelines for rational...

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 exposes a procedure to couple multiport transfer matrices to finite elements for analyzing the acoustics of automotive hollow body networks with a minimum of memory requirements and computa-tional time. Generally, hollow body networks are made up from a series of elongated fluid partitions sim-ilar to ducts or waveguides. These fluid par...

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...

Closed-cell metallic foams are known for their rigidity, lightness, thermal conductivity as well as their low production cost compared to open-cell metallic foams. However, they are also poor sound absorbers. Similarly to a rigid solid, a method to enhance their sound absorption is to perforate them. This method has shown good preliminary results b...

The paper discusses a method of characterizing a source of hydraulic pressure pulsations. The source is characterized within a particular hydraulic test rig by its blocked pressure and internal impedance. The method uses the principle of multiple charges to identify the source pressure and impedance via an inverse procedure. The test rig contains a...

La mesure directe du champ de pression pariétale généré par une couche limite turbulente (CLT) sur une structure requiert l'utilisation de microphones affleurants ou déportés, nécessitant une paroi instrumentée spécifique. Une estimation indirecte de ce type d'excitation pourrait permettre de s'affranchir de l'instrumentation de la paroi. La méthod...

Les matériaux poreux utilisés pour leur qualité d'absorption sonore sont couramment assemblés avec une couche résistive. Cette couche est parfois ajoutée pour augmenter les performances acoustiques du matériau mais elle est le plus souvent utilisée à des fins de protection ou de décoration. Par exemple les laines de roches, connues comme de bons ab...

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...