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2016-06-15
Technical Paper
2016-01-1854
Johannes Seifriedsberger, Rudolf Wichtl, Helmut Eichlseder
Abstract The present article is concerned with the investigation of the engine noise induced by the piston slap of an actual passenger car Diesel engine. The focus is put on the coherence of piston secondary movement, impact of the piston on the cylinder liner, generated structure-borne noise excitation of the engine structure and the occurring acceleration on the engine surface. Additionally, the influence of a varying piston-pin offset and piston clearance is evaluated. The analyses are conducted using an elastohydrodynamic multi-body simulation model, taking into account geometry, stiffness and mass information of the single components as well as considering elastic and hydrodynamic behavior of the piston-liner contact. A detailed description of the simulation model will be introduced in the article. The obtained results illustrate the piston secondary motion and the related structure-borne noise on the engine surface for several piston-pin offsets and piston clearances.
2016-06-15
Technical Paper
2016-01-1845
Xueji Zhang, ZhongZhe Dong, Martin Hromcik, Kristian Hengster-Movric, Cassio Faria, Herman D. Van der Auweraer, Wim Desmet
Active vibration reduction for lightweight structures has attracted more and more attention in automotive industries. In this paper, reduced-order controllers are designed based on H∞ techniques to realize vibration reduction. A finite element model of piezo-based smart structure is constructed from which a nominal model containing 5 modes and validation model containing 10 modes are extracted. A mixed-sensitivity robust H∞ controller is firstly designed based on the nominal structural model. Considering the ease of controller deployment, an order reduction for the controller is then exploited using balanced truncation method. The effectiveness of the reduced-order controller is finally verified on the validation model via system simulations.
2016-06-15
Technical Paper
2016-01-1849
Arnaud Caillet, Luca Alimonti, Anton Golota
Abstract The need for the industry to simulate and optimize the acoustic trim parts has increased during the last decade. There are many approaches to integrate the effect of an acoustic trim in a finite element model. These approaches can be very simple and empirical like the classical non-structural mass (NSM) combined to a high acoustic damping value in the receiver cavity to much more detailed and complex approach like the Poro-Elastic Materials (PEM) method using the Biot parameters. The objective of this paper is to identify which approach is the most appropriate in given situations. This article will first make a review of the theory behind the different methods (NSM, Impedances, Transfer Matrix Method, PEM). Each of them will be investigated for the different typical trim families used in the automotive industry: absorber, spring/mass, spring/mass/absorber.
2016-06-15
Technical Paper
2016-01-1848
Jean-Loup Christen, Mohamed Ichchou, Olivier Bareille, Bernard Troclet
Abstract The problem of noise transmission through a structure into a cavity appears in many practical applications, especially in the automotive, aeronautic and space industries. In the mean time, there is a trend towards an increasing use of composite materials to reduce the weight of the structures. Since these materials usually offer poor sound insulation properties, it is necessary to add noise control treatments. They usually involve poroelastic materials, such as foams or mineral wools, whose behaviour depends on many parameters. Some of these parameters may vary in rather broad ranges, either because of measurement uncertainties or because their values have not been fixed yet in the design process. In order to efficiently design sound protections, performing a sensitivity analysis can be interesting to identify which parameters have the most influence on the relevant vibroacoustic indicators and concentrate the design effort on them.
2016-06-15
Technical Paper
2016-01-1851
Arnaud Duval, Minh Tan Hoang, Valérie Marcel, Ludovic Dejaeger
Abstract 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.
2016-06-15
Technical Paper
2016-01-1850
Christian Thomas, Nouredine Atalla
In passenger aircraft the most important noise control treatment is the primary insulation attached to the fuselage. Next to its acoustic properties the primary insulation main purpose is the thermal insulation and the minimization of condensed water. In general it consists of fibrous materials like glass wool wrapped in a thin foil. Due to stringent flame, smoke and toxicity requirements the amount of available materials is limited. Furthermore the amount of material installed in aircraft per year is much smaller compared to needs in the automotive industry. Therefore the best lay-up of the available materials is needed in terms of acoustics. This paper presents a tool for numerical optimization of the sound insulation package. To find an improved insulation the simulation tool is used in interaction with a measurement database. The databank is constructed from aircraft grade materials such as fibrous materials, foams, resistive screens and impervious heavy layers.
2016-06-15
Technical Paper
2016-01-1853
Timo Hartmann, Gregor Tanner, Gang Xie, David J. Chappell
Abstract Car floor structures typically contain a number of smaller-scale features which make them challenging for vibro-acoustic modelling beyond the low frequency regime. The floor structure considered here consists of a thin shell floor panel connected to a number of rails through spot welds leading to an interesting multi-scale modelling problem. Structures of this type are arguably best modelled using hybrid methods, where a Statistical Energy Analysis (SEA) description of the larger thin shell regions is combined with a finite element model (FEM) for the stiffer rails. In this way the modal peaks from the stiff regions are included in the overall prediction, which a pure SEA treatment would not capture. However, in the SEA regions, spot welds, geometrically dependent features and directivity of the wave field are all omitted. In this work we present an SEA/FEM hybrid model of a car floor and discuss an alternative model for the SEA subsystem using Discrete Flow Mapping (DFM).
2016-06-15
Technical Paper
2016-01-1804
Stefan Becker, Katrin Nusser, Marco Oswald
Abstract Aim of the ongoing development of passenger cars is to predict the interior acoustics early in the development process. A significant noise component results from the flow phenomena in the area of the side window. Wind noise is a physical problem that involves the three complicated aspects each governed by different physics: The complex turbulent flow field in the wake of the a-pillar and the side mirror is characterized by velocity and pressure fluctuations. The flow field generates sound which is transmitted into the passenger cabin. In addition to that, it excites the structure, resulting in a radiation of structure-borne noise into the interior of the car. Therefore, the sound generation is governed by fluid dynamics of the air flow. The sound transmission through the structure due to vibrations is determined by structural mechanics of the body structure. The sound propagation inside the cabin is influenced by interior room acoustics.
2016-06-15
Technical Paper
2016-01-1830
Denis Blanchet, Luca Alimonti, Anton Golota
Abstract This paper presents new advances in predicting wind noise contribution to interior SPL in the framework of the Wind Noise German Working Group composed of Audi, Daimler, Porsche and VW. In particular, a new approach was developed that allows to fully describe the wind noise source using CFD generated surface pressure distribution and its cross-correlation function and apply this source on an SEA side glass. This new method removes the need to use a diffuse acoustic field or several plane waves with various incidence angle to approximate the correct acoustics source character to apply on the SEA side glass. This new approach results are compared with results previously published which use more deterministic methods to represent the side glass and the interior of a vehicle.
2016-06-15
Technical Paper
2016-01-1800
Xavier Carniel, Anne Sanon
Abstract The control of sound fields radiated by vibrating structures in a passenger compartment, (especially structures connected to different organs like the engine powertrain, the fan motor unit, seats, the steering column, electrical motors more and more, etc.) is among the functions of the automotive manufacturers. The absence of physical prototypes in the development phase systems led OEMs1 to use tests results obtained on benches following technical specifications from manufacturers. The transition "bench to vehicle" for vibro- acoustic behaviour sets many challenges that this standard intends to clear up. This standard specifies the experimental method to transpose the dynamic forces generated by the global movements of an active component between the vehicle and a test bench. The efforts are first measured on test benches and then transposed from test bench towards the vehicle. The standard is now a French standard (XP R 19-701) and is submitted to ISO process [1].
2016-06-15
Technical Paper
2016-01-1836
Sylvestre Lecuru, Pascal Bouvet, Jean-Louis Jouvray, Shanjin Wang
Abstract The recent use of electric motors for vehicle propulsion has stimulated the development of numerical methodologies to predict their noise and vibration behavior. These simulations generally use models based on an ideal electric motor. But sometimes acceleration and noise measurements on electric motors show unexpected harmonics that can generate acoustic issues. These harmonics are mainly due to the deviation of the manufactured parts from the nominal dimensions of the ideal machine. The rotor eccentricities are one of these deviations with an impact on acoustics of electric motors. Thus, the measurement of the rotor eccentricity becomes relevant to understand the phenomenon, quantify the deviation and then to use this data as an input in the numerical models. An innovative measurement method of rotor eccentricities using fiber optic displacement sensors is proposed.
2016-06-15
Technical Paper
2016-01-1786
Per Alenius, Magnus Olsson, Thomas Lindbom
Abstract Highly refined NVH (Noise, Vibration and Harshness) is a key attribute for premium segment passenger cars. All noise sources such as powertrain, tires, wind, climate unit and etc. must be well balanced and at such a low level that the customer expectations are met or exceeded. However, not only are the NVH levels of importance but the character of the noise must also meet the high demands from premium car customers. This is especially true for diesel engines which historically have been more prone to have a less refined engine noise character than petrol engines. This paper will describe an investigation of what is defined as “engine presence” in four-cylinder diesel engine cars. The scope is to define a method for consistent subjective assessment of engine presence and to find the relationship and investigate the correlation between the “perceived loudness”, “perceived harshness” and the overall engine presence interior of the car.
2016-06-15
Technical Paper
2016-01-1834
Florian Fink, Gregor Koners
Abstract This paper describes the prediction process of wheel forces and moments via indirect transfer path analysis, followed by an analysis of the influence of wheel variants and suspension modifications. It proposes a method to calculate transmission of noise to the vehicle interior where wheel forces and especially moments were taken into account. The calculation is based on an indirect transfer path analysis with geometrical modifications of the frequency response functions. To generate high quality broadband results, this paper also points out some of the main clearance cutting criteria. The method has been successfully implemented to show the influence of wheel tire combinations as well as the influence of suspension modifications. Case studies have been performed and will be presented in this paper. Operational noise and vibration measurements have been carried out on Daimler NVH test tracks. The frequency response functions were estimated in an acoustic laboratory.
2016-06-15
Technical Paper
2016-01-1783
Oliver Engler
Mercedes-AMG GmbH specializes in unique, high-performance vehicles. The image of AMG as the successful performance brand of Mercedes-Benz is reflected in its impressive successes in the world of motorsport and its unique vehicles. One of these vehicles is the SLS AMG Coupé Electric Drive. After an elaborate series of tests as well as numerous test drives, we have created the SLS eSound which captures the exceptional dynamism of this unique super sports car with electric drive. Starting with a characteristic start-up sound, which rings out on pressing the "Power" button on the AMG DRIVE UNIT, the occupants can experience a tailor-made driving sound for each driving situation: incredibly dynamic when accelerating, subdued when cruising and as equally characteristic during recuperation. The sound is not only dependent on road speed, engine speed and load conditions, but also reflects the driving situation and the vehicle's operating state with a suitable driving noise.
2016-06-15
Technical Paper
2016-01-1843
Jan Krueger, Viktor Koch, Ralf Hoelsch
Abstract Over the past few years, the measurement procedure for the pass-by noise emission of vehicles was changed and new limit values have been set by the European Parliament which will come into force within the next few years. Moreover, also the limits for chemical emissions such as NOx, particulates and CO2 have been lowered dramatically and will continue to be lowered according to a roadmap decided not only in Europe but also in other markets throughout the world. This will have an enormous impact on the design of future passenger cars and in particular on their powertrains. Downsizing, downspeeding, forced induction, and hybridization are among the most common general technology trends to keep up with these challenges. However, most of these fuel saving and cleaner technologies also have negative acoustic side effects.
2016-06-15
Technical Paper
2016-01-1780
Francesca Ronzio, Theophane Courtois
Abstract In automotive acoustics, body NVH design is traditionally carried out without considering the acoustic trim parts. Nevertheless, the vibro-acoustic interaction of body structure and insulation trim cannot be neglected in the middle frequency range, where structure borne propagation might still be dominating and where classical statistical approaches are generally not able to represent the influence of local changes in stiffness and damping. This, together with the market requirement of lightweight and more efficient sound package solutions, is leading the CAE engineers to evaluate new design approaches dedicated to vehicle components such as dash or floor systems, for which the multi-physics interaction between damping, body stiffness and trim impedance is important.
2016-06-15
Technical Paper
2016-01-1807
Olga Roditcheva, Lennart Carl Lofdahl, Simone Sebben, Pär Harling cEng, Holger Bernhardsson
Abstract This paper presents an experimental study of aeroacoustical sound sources generated by the turbulent flow around the side mirror of a Volvo V70. Measurements were carried out at the Volvo Cars aerodynamical wind tunnel (PVT) and at the aeroacoustical wind tunnel of Stuttgart University (FKFS). Several different measurement techniques were applied in both tunnels and the results were compared to each other. The configurations considered here were: side mirror with a cord and without the cord. The results discussed in this paper include intensity probe measurements in the flow around the side mirror, sound source localization with beamforming technique using a three-dimensional spherical array as well as standard measurements inside the car with an artificial head. This experimental study focused on understanding the differences between testing at the PVT and FKFS.
2016-06-15
Technical Paper
2016-01-1832
Ramakrishna Kamath
Intermediate shaft assembly is used to connect steering gear to the steering wheel. The primary function of the intermediate shaft is to transfer torsional loads. There is a high probability of noise propagating through the Intermediate shaft to the driver. The current standard for measuring the noise is by performing vehicle level subjective evaluations. If improperly clamped at either of the yokes, a sudden change in the direction of the torsional load on the Intermediate shaft can generate a displeasing noise. Noise can also be generated from the constant velocity joint. Intermediate shaft noise can be measured using a microphone or can be correlated to acceleration values. The benefit of measuring the acceleration over sound pressure level is the reduction of complexity of the test environment and test set up. The nature of the noise in question requires the filtering of low frequency data. This paper presents a new test procedure that has been developed by General Motors.
2016-06-15
Journal Article
2016-01-1774
Gert Herold, Thomas Geyer, Philipp Markus, Ennes Sarradj
Abstract The sound power level is the most important quantity that characterizes the noise emission of machinery. Following standardized procedures, it is usually calculated from sound pressure levels measured at a number of reference positions on a surface enveloping the object. The resulting value does not hold any direct information on the noise contributions of subcomponents. However, effective noise reduction necessitates a prior identification of acoustic sources and their characteristics. Combining the enveloping-surface method with microphone array measurements facilitates the evaluation of synchronously noise-emitting subcomponents. The application of this technique on a water pump with a four-stroke engine as power source is presented in this paper. The microphones are arranged on a cuboid surface surrounding the setup. The measured data is processed so as to yield sound power levels in a defined 3D focus region.
2016-06-15
Journal Article
2016-01-1766
Thomas Deighan, Nozomu Kato, Kiyofumi Sato
Abstract An engine configuration has a significant influence on the sound quality from the powertrain. Whilst the fundamental order content can be readily apparent from the firing order over the engine, or bank of a V engine, some characteristics and how the engine design can influence them requires some more specific investigation. Understanding, on a fundamental level, the aspects of the engine design which influence these characteristics is critical to allow more detailed analysis and development work to be focused appropriately. The configuration of a Boxer engine gives a distinctive sound characteristic producing a unique sound compared to an In-Line configuration. Depending on the application it may be desirable to enhance or subdue some of these characteristics.
2016-06-15
Journal Article
2016-01-1791
Noé F. Melo, Claus Claeys, Elke Deckers, Bert Pluymers, Wim Desmet
Abstract The NVH performance of conventional panels and structures is mainly driven by their mass. Silence often requires heavy constructions, which conflicts with the emerging trend towards lightweight design. To face the challenging and often conflicting task of merging NVH and lightweight requirements, novel low mass and compact volume NVH solutions are required. Vibro-acoustic metamaterials with stopband behavior come to the fore as possible novel NVH solutions combining lightweight requirements with superior noise and vibration insulation, be it at least in some targeted and tunable frequency ranges, referred to as stopbands. Metamaterials are artificial materials or structures engineered from conventional materials to exhibit some targeted performance that clearly exceeds that of conventional materials. They consist typically of (often periodic) assemblies of unit cells of non-homogeneous material composition and/or topology.
2016-06-15
Journal Article
2016-01-1795
Charly Faure, Charles Pezerat, Frédéric Ablitzer, Jérôme Antoni
In this paper, a local method of structure-borne noise source characterization is presented. It is based on measurements of transverse displacement and local structural operator knowledge and allows to localize and quantify sources without any need of boundary condition information. To fix the instability caused by measurement noise, the regularization step inherent to inverse problem is realized with a probabilistic approach, within the Bayesian framework. When a priori distributions about noise and sources are considered as Gaussian, the Bayesian regularization is equivalent to the well-known Tikhonov regularization. The optimization of the regularization is then performed by the Gibbs Sampling (GS) algorithm, which is part of Markov Chain Monte Carlo (MCMC) techniques. The whole probability of the regularized solution is inferred, providing access to confidence intervals.
2016-06-15
Journal Article
2016-01-1799
Corentin Chesnais, Nicolas Totaro, Jean-Hugh Thomas, Jean-Louis Guyader
Abstract The source field reconstruction aims at identifying the excitation field measuring the response of the system. In Near-field Acoustic Holography, the response of the system (the radiated acoustic pressure) is measured on a hologram using a microphones array and the source field (the acoustic velocity field) is reconstructed with a back-propagation technique performed in the wave number domain. The objective of the present works is to use such a technique to reconstruct displacement field on the whole surface of a plate by measuring vibrations on a one-dimensional holograms. This task is much more difficult in the vibratory domain because of the complexity of the equation of motion of the structure. The method presented here and called "Structural Holography" is particularly interesting when a direct measurement of the velocity field is not possible.
2016-06-15
Journal Article
2016-01-1801
Jonathan Vaudelle, Florian Godard, Florian Odelot, Anne Sanon
Abstract Acoustic comfort inside the vehicle is required whenever a wiper system is in function: front wiper motor noise is of great influence on the global comfort and its perception inside the car is 100% due to transmission of vibrations through wiper system fixation points on the vehicle. As any active source, both car manufacturer and system supplier need to be involved, at early stages of project development, in order to master the vibroacoustic integration of the system into the vehicle. This paper presents an experimental methodology dedicated to the front wiper system that offers the possibility to estimate the acoustic comfort inside the vehicle during project deployment phase, when modifications can still be proposed. Based on the XP-R-19701 standard, the procedure allows to measure, on a bench, the dynamic forces transmitted via the fixation points and details how to transpose them to the vehicle, taking into account the different specificities of the wiper system.
2016-06-15
Journal Article
2016-01-1777
Sebastian Oberst, Zhi Zhang, Joseph CS Lai
Abstract Despite significant progress made in the past 20 years in discovering some of the mechanisms of brake squeal, it remains difficult to predict the underlying friction-induced instabilities reliably. Most numerical analyses are based on linear deterministic analyses of structural vibrations such as the complex eigenvalue analysis (CEA). However, nonlinear multi-scale processes govern friction contact with high sensitivities to operating and/or environmental conditions. In addition, uncertainties in the material properties and boundary conditions such as contact and friction laws are rarely considered. Hence, it is quite common to underpredict or overpredict the number of instabilities and extensive brake noise dynamometer tests are still required in industry to ensure acceptable brake noise performance. In this paper, simplified finite element brake models are used to illustrate the role of nonlinearity in brake squeal.
2016-06-15
Journal Article
2016-01-1778
Gesche Fender, Steffen Marburg, Fabian Duddeck
Abstract One method to lower noise in a cabin is to position damping layers on vibrating panels, thereby reducing their radiated power. To assess the damping effect, criteria like the ERP (equivalent radiated power) are widely employed, which estimate the radiated sound power of a panel without taking into account the actual complex system. Advantageously only a part of the structure has to be modeled, but the optimal solution found on the simplified model then often fails for the complete, coupled system, especially if several variants of a cabin have to be considered. Hence, it is proposed to use the structure-only optimization for identification of a set of candidate solutions for optimal positioning of damping layers. These candidate solutions used as initial designs for the coupled investigations should be well distributed in the design space to avoid being wrongly stuck in an optimum with inferior coupled performance.
2016-06-15
Journal Article
2016-01-1784
Alessandro Fortino, Lutz Eckstein, Jens Viehöfer, Jürgen Pampel
Abstract Vehicles powered by electric machines offer the advantage to be more silent than vehicles equipped with an internal combustion engine. On the one hand, the reduced noise levels enable an improvement of the inner-city noise pollution. On the other hand, quiet vehicles entail risks not to be acoustically detected by surrounding pedestrians and cyclists in the lower speed range. The emitted noise can easily be masked by the urban background noise. Therefore, the UNECE has founded an informal working group which is currently developing guidelines in terms of an exterior noise required for detecting Quiet Road Transport Vehicles (QRTV). With the introduction of an Acoustic Vehicle Alerting System (AVAS), not only the exterior noise but also the perceived interior noise for an enhanced driving experience can be considered. Nevertheless, car manufactures have a big interest in maintaining their perceived brand identity.
2016-06-15
Journal Article
2016-01-1819
Antonio J. Torregrosa, Alberto Broatch, Vincent Raimbault, Jerome Migaud
Abstract Intake noise has become one the main concerns in the design of highly-supercharged downsized engines, which are expected to play a significant role in the upcoming years. Apart from the low frequencies associated with engine breathing, in these engines other frequency bands are also relevant which are related to the turbocharger operation, and which may radiate from the high-pressure side from the compressor outlet to the charge air cooler. Medium frequencies may be controlled with the use of different typologies of resonators, but these are not so effective for relatively high frequencies. In this paper, the potential of the use of multi-layer porous materials to control those high frequencies is explored. The material sheets are located in the side chamber of an otherwise conventional resonator, thus providing a compact, lightweight and convenient arrangement.
2016-06-15
Journal Article
2016-01-1788
Charles Pezerat
Abstract Identification of vibration sources, defects and/or material properties consists generally in solving inverse problems. The called RIFF method (French acronym meaning Windowed and Filtered Inverse Solving) is one way to solve this kind of inverse problem. The basic principle of the RIFF approach consists in measuring vibration displacement on a meshgrid in a local area of interest, injecting measured data in the motion equation and calculating the searched unknown. Compared to other usual inverse techniques, the RIFF method has the curious particularity of needing the knowledge of the local motion equation only. Boundary conditions, sources or dynamic behaviors outside the area of interest can be completely ignored, whereas they are required for the direct problem solving. The searched unknown can then be identified locally with respect to the frequency and can be mapped by using a scanning process of the area of interest.
2016-06-15
Journal Article
2016-01-1825
Jung-Han Woo, Da-Young Kim, Jeong-Guon Ih
Abstract To hear the powerful and spectrally rich sound in a car is costly, because the usual car audio system adopts small loudspeakers. Also, the available positions of the loudspeakers are limited, that may cause the reactive effect from the backing cavity and the sound distortion. In this work, a part of the roof panel of a passenger car is controlled by array actuators to convert the specified large area to be a woofer. An analogous concept of the acoustic holography is employed to be projected as the basic concept of an inverse rendering for achieving a desired vibration field. The vibration of the radiating zone is controlled to be in a uniform phase, and the other parts outside it are to be made a no-change zone in vibration. The latter becomes a baffle for the woofer, and the backing cavity is virtually infinite if the sound radiation into the passenger cabin is only of concern.
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