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Fast Broadband Curved Insertion Loss Simulation of an Inner Dash Insulator Using a Cylindrical Transfer Matrix Method Spectral Approach

Interac-Gerard Borello
Treves-Arnaud Duval, Mickael Goret
Published 2019-06-05 by SAE International in United States
Middle and high frequency vibro-acoustic simulation of complex shape insulators requires using 3D poroelastic finite elements. This can be applied to either the whole part (up to 2500 Hz maximum) or through singly curved pre-computed Insertion Losses (up to 5000 Hz maximum) to be introduced in large SEA or energy-based models. Indeed, a dependence of the Insertion Loss slopes of noise treatments following the curvature is observed both experimentally and numerically. Beyond frequency range limitations, poroelastic finite element simulations following all curvatures and thickness 3D maps typically take too much time of up to a few hours each. A cylindrical Transfer Matrix Method spectral approach significantly reduces the time for the calculation of singly curved Insertion Losses up to 10 kHz to only a few minutes. This simplifies enormously the SEA modeling effort enabling easier, more precise fully trimmed vehicle middle and high frequency vibro-acoustic simulations. A dash insulator Insertion Loss numerical validation case will be presented comparing the different methods.
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Ecofelt Hybrid Stiff NVH Tunable Insulator

PSA Peugeot Citroën-Jean-Baptiste Prunet, Patrick Chanudet
Treves-Arnaud Duval, Guillaume Crignon, Mickael Goret, Dominique Lemaire
Published 2018-06-13 by SAE International in United States
Whenever the noise source level or the expected acoustic comfort increases for diesel engines for example or for premium petrol vehicles, the required weight per unit area can be specified above 2000 g/m2 for the equivalent barrier of a mixed absorbing-insulating noise treatment. For an ABA foam/heavy layer/felt insulator, this is not a big issue, one has to increase the intermediate heavy layer weight. For hybrid stiff compressed felt backfoamed standard technologies, going above 2000 g/m2 is critical due to absorption properties loss following much too high airflow resistances and progressive porosity loss (above 250 kg/m3) as well as too high bending stiffness presenting resonant modes progressively and assembly manipulation issues. Last but not least, compressed felts begin to present too high costs at these weights against those of the heavy layers of ABA systems.The chips urethanes give an answer to the aforementioned issues for high weights above 2000 g/m2 up to 3500 g/m2 typically for hybrid stiff backfoamed concepts in the same mold and with the same process as lower weights (called Polyfoam). The acoustic properties of these highly…
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Comprehensive Hybrid Stiff Insulators Family: The Chips Urethane Contribution

Treves-Arnaud Duval, Guillaume Crignon, Mickael Goret, Maxime Roux
Published 2017-06-05 by SAE International in United States
The lightweighting research on noise treatments since years tends to prove the efficiency of the combination of good insulation with steep insulation slopes with broadband absorption, even in the context of bad passthroughs management implying strong leakages. The real issue lies more in the industrial capacity to adapt the barrier mass per unit area to the acoustic target from low to high segment or from low petrol to high diesel sources, while remaining easy to manipulate. The hybrid stiff insulator family can realize this easily with hard felts barriers backfoamed weighting from 800 g/m2 to 2000 g/m2 typically with compressions below 10 mm.Above these equivalent barrier weights and traditional compressions of 7 mm for example, the high density of the felts begins to destroy the open porosity and thus the absorption properties (insulation works anyway here, whenever vibration modes do not appear due to too high stiffness…). The felt costs begin to be critical for these intermediate weights above 2000 g/m2 as well. From 2000 g/m2 up to 3000 g/m2 or 3500 g/m2 equivalent barriers,…
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Carpet Hybrid Foam Spacer: An Ultra-Absorbing Lightweight Floor Insulator

Faurecia Acoustics and Soft Trim Div.-Arnaud Duval, Minh Tan Hoang, Valérie Marcel, Ludovic Dejaeger
Published 2016-06-15 by SAE International in United States
The noise treatments weight reduction strategy, which consists in combining broadband absorption and insulation acoustic properties in order to reduce the weight of barriers, depends strongly on surface to volume ratio of the absorbing layers in the reception cavity. Indeed, lightweight technologies like the now classical Absorber /Barrier /Absorber layup are extremely efficient behind the Instrument Panel of a vehicle, but most of the time disappointing when applied as floor insulator behind the carpet.This work aims at showing that a minimum of 20 mm equivalent “shoddy” standard cotton felt absorption is requested for a floor carpet insulator, in order to be able to reduce the weight of barriers. This means that a pure absorbing system that would destroy completely the insulation properties and slopes can only work, if the noise sources are extremely low in this specific area, which is seldom the case even at the rear footwells location. The proposed Carpet hybrid foam spacer technology is answering to the question by using the hybrid foam-foam 3D solution, applied as floor insulator with encapsulated rigid…
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Vibro-Acoustic Properties of a Very Long Flax Fibers Reinforced Thermoset “Flaxpreg” Light Sandwich

Faurecia Acoustics And Soft Trim Div.-Arnaud Duval, Valérie Marcel, Ludovic Dejaeger, Francis Lhuillier, Moussa Khalfallah
Published 2015-06-15 by SAE International in United States
The Flaxpreg is a green and light very long flax fibers thermoset reinforced sandwich, which can be effectively used as multi-position trunk loadfloor or structural floor in the passenger compartment of a vehicle. The prepreg FlaxTapes of about 120 g/m2 constituting the skins of the sandwich, are unidirectionally aligned flax fibers tapes, with acrylic resin here, easily manipulable without requiring any spinning or weaving step and thus without any negative out of plane crimping of the almost continuous flax fibers.Thanks to their very low 1.45 kg/dm3 density combined with an adaptive 0°/90°/0° orientation of the FlaxTapes (for each skin) depending on the loading boundary conditions, the resulting excellent mechanical properties allow a - 35% weight reduction compared to petro-sourced Glass mat/PUR sandwich solutions (like the Baypreg). The vibro-acoustic damping properties of these FlaxTape skins are remarkable with an almost 2 % Damping Loss Factor, whereas glass/resin or carbon/resin composites lie at around 0.15%.This study presents a comprehensive measurement and simulation correlation campaign of the vibro-acoustic properties of the Flaxpreg sandwich, namely its Damping Loss Factor…
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Generalized Light-Weight Concepts: A New Insulator 3D Optimization Procedure

Faurecia Acoustics and Soft Trim Div.-Arnaud Duval, Jean-Francois Rondeau, Ludovic Dejaeger, Francis Lhuillier, Julien Monet-Descombey
Published 2013-05-13 by SAE International in United States
In order to reach the new 2020 CO2 emissions regulations, we have developed a wide range of lightweight noise treatment technologies going from pure absorbing to highly insulating ones, depending on the pass-through quality situation. This Generalized Light-Weight Concepts family was first optimized using the 2D Transfer Matrix Method (TMM) combined with quick SEA approaches. Taking into account thickness 3D maps with TMM is an efficient and quick intermediate “2,5D” optimization method, but it is not a real 3D approach.This work presents a new 3D optimization procedure based on poroelastic finite elements including intermediate cavities (like Instrument Panels) for designing these Generalized Light-Weight Concepts. A parallel reflection deals with products and processes in order to check the feasibility of the resulting 3D optimized insulator designs. Indeed, playing with multi-layer insulators (typically three to four layers) leads to some design difficulties for the low thicknesses, typically below 10 mm, especially for felt layers for which a maximum compression rate exists.This 3D optimization procedure takes into account the design freedom offered by each porous material technology, like…
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Trim FEM Simulation of a Headliner Cut Out Module with Structureborne and Airborne Excitations

Faurecia Acoustics and Soft Trim Product Line-Arnaud Duval, Ludovic Dejaeger, Lars Bischoff, Christian Morgenstern
Published 2012-06-13 by SAE International in United States
Due to increasing attention paid to the optimization of leakages and passthroughs in general, measurements on cut out modules in large coupled reverberant rooms are often carried out in the middle and high frequency range, in order to optimize the insulation performance of trims installed in their actual environment (Transmission Loss). Using optimal controlled mounting conditions, we have been able to extend the frequency range to the low frequencies in order to validate trim FEM models of a headliner cut out module with structureborne and airborne excitations.Both coupled response with movable concrete cavities (structureborne excitation) and Transmission Loss with coupled reverberant rooms (airborne excitation), or pure acoustic response with a monopole source positioned in the movable concrete cavity (airborne excitation in order to quantify absorption effects), have been measured and simulated using poroelastic finite elements for various types of trims on the same setup, without any change on the mounting conditions. An additional movable absorbing environment in the large reception room has been deployed in order to carry out laser vibrometer (skeleton velocity) and p-u…
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Generalized Light-Weight Concepts: Improving the Acoustic Performance of Less than 2500 g/m2 Insulators

FAURECIA-Arnaud Duval, Jean-François Rondeau, Lars Bischoff, Guillaume Deshayes, Ludovic Dejaeger
Published 2009-05-19 by SAE International in United States
The weight reduction challenge has taken a new shape in the past two years due to high pressure on CO2 emissions in the automotive industry. The new question is: what level of acoustic performance can you get with an insulator weighting less than 2500 g/m2? The existing solutions at this weight being mainly dissipative (absorption) concepts give a satisfactory performance only if the pass-throughs are poor and present critical leakages.Respecting the less than 2500 g/m2 weight target, we have developed a wide range of new or optimized concepts switching from extremely absorbing to highly insulating noise treatments playing with multi-layers insulators (typically three to four layers), in combination or not with tunable absorbers on the other side of the metal sheet (in the engine compartment for example). Each system answers a specific pass-through quality situation, the best concepts combining broadband absorption with good insulation slopes, which oblige to develop very light airflow resistive non-wovens and light airtight barriers in parallel to optimized poroelastic materials like foams or felts.This paper illustrates various applications of these Generalized…
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SONVERT: Hybrid Traffic Noise Simulation Approach

CSTB-Philippe Jean, Nicolas Noe
ESI-FRANCE-Slaheddine Frikha, Alexandre Gallet
Published 2009-05-19 by SAE International in United States
The purpose of the SONVERT project is to create a link between the acoustical sources of a car and the environment in terms of traffic and architecture. Based on well validated approaches, it introduces the notion of a “macro-source” which integrates the major acoustic sources: engine, tires and exhaust, taking into account the low and high frequency aspects, from measurements made on real vehicles. The macro-source is then integrated into an original approach dealing with outdoor propagation. The proposed method can consequently be seen as a first step toward a global approach for the study of traffic noise in real conditions.
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Vehicle Acoustic Synthesis Method 2nd Generation: New Developments with p-u Probes Allowing to Simulate Unsteady Operative Conditions Like Run-Ups

FAURECIA-Arnaud Duval, J-F. Rondeau, L. Bischoff, Ch. Morgenstern, G. Deshayes
PSA Peugeot Citroën-Laurent Gagliardini
Published 2007-05-15 by SAE International in United States
The challenge of a NVH development is to define a link between the target of the OEMs expressed in terms of acoustic performance, weight and cost and the design of the optimized acoustic package reaching this target. The “Vehicle Acoustic Synthesis Method” (VASM) has been developed in order to create this link. The VASM method, which is an energy based hybrid simulation technique, calculates the Sound Pressure Level at ear location from the combination of sound power measurements and acoustic frequency response functions (FRF) panel/ear, either measured or simulated with Ray-Tracing Methods.This paper deals with the last developments of the 2nd generation of the “Vehicle Acoustic Synthesis Method” (VASM 2) using p-u pressure-particle velocity probes, for both sound intensity and transfer functions measurements, in order to speed-up the time to build a model of a fully trimmed vehicle in the middle and high frequency range, while increasing accuracy both in terms of source localization and source quantification and while addressing unsteady operating conditions like run-ups.Intensity measurements inside a car in operative conditions give access to…
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