Publications

To build accurate NVH predictive simulation models of cars, airplanes, train cabins and the like, one has to properly represent the geometry of the structure, the acoustic fluid and the sound package. Furthermore, the model must contain accurate physical properties of the material used. Those physical properties are readily available for the structural elements but it is not the case for the sound package.

Integration of acoustic material concepts into vehicle design process is an important part of full vehicle design. The ability to assess the acoustic performance of a particular sound package component early in the design process allows designers to test various design concepts before selecting a final solution and long before a design freeze.

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.

The coupled structural-acoustic Boundary Element Method (BEM) has been widely used in vibro-acoustic analysis for decades now, due to its ease of model set up and low dispersion error characteristics. Recently, evolutions of BEM to solve Aero-Vibro-Acoustic (AVA) problems have been introduced.

The coupled structural-acoustic Boundary Element Method (BEM) has been widely used in vibro-acoustic analysis for decades now, due to its ease of model building and high accuracy. Recently, evolutions of BEM to solve large Aero-Vibro-Acoustic (AVA), space and underwater problems have been introduced.

Recent developments in the prediction of the contribution of wind noise to the interior SPL (Sound Pressure Level) have opened a realm of new possibilities. The main physical mechanisms related to noise generation within a turbulent flow and the transmission through the vehicle greenhouse are nowadays better understood and can be easily and accurately modelled.

Recent developments in the prediction of the contribution of wind noise to the interior SPL have opened a realm of new possibilities. The main physical mechanisms related to noise generation within a turbulent flow and the vibro-acoustic transmission through the vehicle greenhouse is nowadays better understood. Several simulation methods such as CFD, FEM, BEM, FE/SEA Coupled and SEA can be coupled together to represent the physical phenomena involved. The main objective being to properly represent the convective and acoustic component within the turbulent flow to ensure proper computation of the wind noise contribution to the interior SPL of a vehicle

KEYNOTE SPEECH: 10 years after first implementation of FEM-SEA coupled

Von einem Konsortium der Fahrzeughersteller Audi, Daimler, Porsche und Volkswagen wurden Messungen und Simulationen an einem generischem Fahrzeugmodell durchgefuhrt, um die Stromungsakustik der am Modell dargestellten Komponenten A-Saule und Spiegel zu untersuchen. Dafur werden Wellenzahlspektren - ermittelt mit 93 Oberflachensensoren in optimierter Anordnung und bundig in ein Seitenscheibenmodul eingebaut - analysiert und mit Simulationen der als kompressibel angenommenen Stromung verglichen.

The marine industry has in the past extensively used empirical models to predict transfer functions between source locations and noise sensitive cabins. These empirical methods work well for standard construction types, materials and small number of cabins. Today's tendencies are to use complex construction methods, exotic material such as composite and build larger and larger yachts with cabin layouts and numbers not easily represented in an empirical way.

Recent developments in the prediction of the contribution of wind noise to the interior SPL have opened a realm of new possibilities in terms of i) how the convective and acoustic sources terms can be identified, ii) how the interaction between the source terms and the side glass can be described and finally iii) how the transfer path from the sources to the interior of the vehicle can be modelled.

Since the last decade, the automotive industry has expressed the need to better understand how the different trim parts interact together in a complete car up to 400 Hz for structureborne excitations. Classical FE methods in which the acoustic trim is represented as non-structural masses (NSM) and high damping or surface absorbers on the acoustic cavity can only be used at lower frequencies and do not provide insights into the interactions of the acoustic trims with the structure and the acoustic volume.

KEYNOTE SPEECH: The evolution of vibro-acoustic simulation methods has allowed engineers to tackle applications that were ever increasing in complexity and sheer size. From the Nastran punch cards to today s cloud computing, the increase in possibilities is mind-blowing and the perspectives for the future of computing have never been so bright.

Recent developments in the prediction of the contribution of windnoise to the interior SPL have opened a realm of new possibilities in terms of i) how the convective and acoustic sources terms can be identified, ii) how the interaction between the source terms and the side glass can be described and finally iii) how the transfer path from the sources to the interior of the vehicle can be modelled.

Turbulent flow generates convective and acoustic pressure fluctuations on side glass, This energy can potentially be transferred inside a vehicle.

Preliminary assessment: Measurements of pressure and STIPA values in the train cabin. Initial train cabin modeling and BEM computation. Simulation improvement: Objectives: Improvement of pressure results accuracy. Assessment of the influence of details in the cabin. Simulation for Speech Transmission Index (STI) results.

Turbulent flow generates convective and acoustic pressure fluctuations on side glass. This energy can potentially be transferred inside vehicle

In the marine industry, simulation starts to occupy a key role in product design as NVH and environmental requirements are becoming increasingly demanding. This paper discusses new advances in marine vibro-acoustic predictions and in particular the effect of seabed topology and material composition on the underwater noise radiation of a steel hull.

There are many applications in which exterior flow over a structure is an important source for interior noise. In order to predict interior wind noise it is necessary to model both: (i) the spatial and spectral statistics of the exterior fluctuating surface pressures (across a broad frequency range) and (ii) the way in which these fluctuating surface pressures are transmitted through a structure and radiated as interior noise (across a broad frequency range). One approach to the former is to use an unsteady CFD model.

There are many applications in which exterior flow over a structure is an important source for interior noise. In order to predict interior wind noise it is necessary to model both: (i) the spatial and spectral statistics of the exterior fluctuating surface pressures (across a broad frequency range) and (ii) the way in which these fluctuating surface pressures are transmitted through a structure and radiated as interior noise (across a broad frequency range).

Noise and vibration simulation using classical methods such as Finite Element Method (FEM), Boundary Element Method (BEM) and Statistical Energy Analysis (SEA) are well integrated into standard design processes in the automotive, aerospace and train industry. In the marine industry, simulation starts to occupy a key role in product design as vibro-acoustics and environmental requirements are becoming increasingly demanding

Noise and vibration simulation using classical methods such as Finite Element Method (FEM), Boundary Element Method (BEM) and Statistical Energy Analysis (SEA) are well integrated into standard design processes in the automotive, aerospace and train industry. In the marine industry, simulation starts to occupy a key role in product design as vibro-acoustics and environmental requirements are becoming increasingly demanding.

Noise and vibration simulation using classical methods such as Finite Element Method (FEM), Boundary Element Method (BEM) and Statistical Energy Analysis (SEA) are well integrated into standard design processes in the automotive, aerospace and train industry. In the marine industry, simulation starts to occupy a key role in product design as vibro-acoustics and environmental requirements are becoming increasingly demanding.

There are many applications in which exterior flow over a structure is an important source for interior noise. In order to predict interior wind noise it is necessary to model both: (i) the spatial and spectral statistics of the exterior fluctuating surface pressures (across a broad frequency range) and (ii) the way in which these fluctuating surface pressures are transmitted through a structure and radiated as interior noise (across a broad frequency range). One approach to the former is to use an unsteady CFD model.

In recent years, low and mid frequency analysis of engine has shown that many design decisions influenced negatively the acoustic performance of engines. To counteract this problem, design engineers have started to design engine covers that actually reduce the noise radiated before it gets too far from the engine. These methods basically modify the path the noise would take to get to a vehicle occupant ear. Another approach is to modify the design of the engine construction itself in order to reduce the noise generated at the source.

The marine industry has used empirical models to predict transfer functions between source locations and noise sensitive cabins extensively in the past. These empirical methods work well for standard construction types, material and small number of cabins. Today tendencies are to use complex construction methods, exotic material such as composite and build larger and larger yachts with cabin layouts and numbers not easily represented in an empirical way.

Wind noise has become in recent years a significant contributor to perceived sound inside automobiles. Many methods are nowadays available to couple wind tunnel or CFD (Computational Fluid Dynamics) data to a full vehicle vibro-acoustic model. This paper presents an overview of these methods and focuses on one specific method which allows the test or CFD data to be used as the source of a SEA (Statistical Energy Analysis) full vehicle model. The paper presents the wind tunnel test data available and how it is used to describe the pressure fluctuation as a SEA (Statistical Energy Analysis) source.

This paper discusses the effect of adding beads to a floor panel in respect to radiated sound inside a vehicle. It also describes the combined effect of using beads and a carpet to meet a predefined SPL (Sound Pressure Level) target at the driver s ear location. It has been widely demonstrated in the literature that adding beads to a floor panel reduces vibration levels at low frequency by shifting the first few modes to a higher frequency.

In the automotive industry, it is common to have different departments designing different parts of the floor. The NVH department may define the overall structural stiffness and might request beading to be added to specific panels to reduce the vibration response locally. It may also request damping pads to be added on the remaining vibration hot spots of the floor. The acoustic group then needs to define the acoustic trim needed to meet the vehicle targets based on the constraints prescribed by the NVH department choices concerning structural stiffness, floor construction, beading, damping pad In many cases, the NVH and acoustic groups are not communicating and some solutions proposed by one group are detrimental to the other group.

In the automotive industry, the use of beading is widely spread. Beads are primarily used to stiffen the floor and dash panels. The aim is to reduce vibration levels and hopefully at the same time reduce radiated noise. Beading has a positive effect close to the first panel mode natural frequency however it can have a negative effect at all other frequencies. Typically, engineers assume a radiation efficiency of 1 (one) over the whole frequency range for simplicity or lack of available implemented formulation in their simulation tools. This assumption directs the investigation at reducing the vibration levels only.

Lightweight composite structures for high-technology applications have to fulfill high demands on low constructive weight combined with an adequate stiffness. In general, the low structural weight leads to high vibration amplitudes due to low forces of inertia and causes an undesired sound radiation. This effect can be compensated by exploiting the high vibro-acoustic potential of fibre-reinforced composites. For this purpose, an integrated calculation algorithm for the transmission loss, considering the eigenfrequencies (modal analysis) and the estimation of modal damping values, is presented.

Traditionally in the automotive industry, the acoustic trim has been modelled using a series of spring/mass/dampers added to an FE description of the structure. This simple method has deficiencies in accuracy even in the low frequency domain and could therefore not be used with confidence as a predictive method over 150 Hz. Other approaches literally ignored the effect of trim on the structure and focused at representing the acoustic trim absorption in the interior fluid.

In various industries, engine design has an important impact on noise radiated by a manufactured product. In recent years, low and mid frequency analysis of engine has shown that many design decisions influenced negatively the acoustic performance of engines. To counteract this problem, design engineers have started to design engine covers that actually reduce the noise radiated before it gets too far from the engine. These methods basically modify the path the noise would take to get to a vehicle occupant ear.

Rapid prototyping requires increased use of simulation Full frequency analysis needed to fully diagnose vibroacoustic performance Minimum computation time to allow optimization Predictive simulation removes need for physical prototype until late in a design process.

In the automotive industry, the influence of poroelastic components on acoustic comfort has been mostly investigated for airborne noise at mid- and high frequency ranges; however, due to the lack of adequate theoretical formulations, the influence of poroelastic in numerical vibroacoustic simulation at lower frequency range has often been ignored or simplified by the use of distributed spring/mass on the BIW structure and impedance on the acoustic medium.

In the automotive industry, the influence of poroelastic components on acoustic comfort has been mostly investigated for airborne noise at mid- and high frequency ranges; however, due to the lack of adequate theoretical formulations, the influence of poroelastic in numerical vibroacoustic simulation at lower frequency range has often been ignored or simplified by the use of distributed spring/mass on the BIW structure and impedance on the acoustic medium.

Experimental and numerical investigations of the fluid-structure interaction as well as the sound, induced by the turbulent flow over a flexible plate structure and radiated to the acoustic far field, are presented. To modify the standard inflow condition that is a fully turbulent boundary layer, an obstacle is placed upstream of a flexible plate. In order to investigate the influence of such a plate on the wall near flow field, the flow-induced vibration of the plate structure is measured using a laser-scanning vibrometer.

Transmission loss modelling plays a vital role in the design of acoustically efficient products. Whether in the aircraft, automotive or train industry, transmission loss measurements and simulation are used to improve the vibro-acoustic performance of components. Since fewer prototypes are built and therefore fewer tests can be made, the accurate prediction of transmission loss over the full frequency range of interest has become increasingly important. Modelling transmission loss of a complex structure involves the use of deterministic methods such as FEM (Finite Element Method) and BEM (Boundary Element Method) at lower frequencies and statistical methods such as SEA (Statistical Energy Analysis) at higher frequencies.

Acoustic comfort in the interior of the trains is a key parameter in the design of modern trains. Moreover, European legislation of interoperability sets limits of interior noise in drivers cab. New hybrid methodologies including coupling between FEM/BEM/SEA make it possible to carry out useful predictions in an industrial environment. ALSTOM is applying these techniques in the development of modern trains to achieve human friendly products for passengers and train personnel.

The interior noise levels in trains has been reduced considerably during the last decades. However, the acoustic behavior has nowadays an even more important role among the comfort parameters of high speed trains. The FE-SEA hybrid methodologies raised up during the last years have given a new approach to the problem of the structure borne noise, giving the opportunity to deal with the acoustic mid frequency range, where FE and SEA systems were unable to work. However this numerical models depend on several physical parameters and, although most of them are well known in fields like the automotive, they need to be further studied for the rolling stock applications.

In the automotive industry, the influence of poroelastic components on acoustic comfort has been mostly investigated for air borne noise at mid- and high frequency ranges. However, due to the lack of adequate theoretical formulations, the influence of poroelastic in numerical vibro-acoustic simulation at lower frequency range has often been ignored or roughly approximated by the addition of distributed spring/mass on the BIW structure.

In the automotive industry, the influence of poroelastic components on acoustic comfort has been mostly investigated for air borne noise at mid and high frequency ranges. However, due to the lack of adequate theoretical formulations, the influence of poroelastic material in numerical vibro-acoustic simulation at lower frequency range has often been ignored or roughly approximated by the addition of distributed spring/mass on the BIW structure.

This paper provides an overview of the building and validation process for an airborne SEA model of a typical automotive vehicle using the AutoSEA2 software. The emphasis is placed on identifying the transmission paths as well as sound package characteristics that are most critical to ensure accurate predictions using SEA. It also compares predictions with experimental results of well controlled load cases. Correlation between predictions and tests is presented and briefly discussed.

In Statistical Energy Analysis (SEA), the sound field in an acoustic subsystem is assumed to be diffuse and reverberant, that is, there is an equal probability for a wave to travel in any direction with equal wave intensity. Although this has proven to be an efficient way of modeling the interior space of a vehicle [1], it is less suitable for external cavity modeling. The main reasons include: a) high directivity pattern of sources such as tire/road noise, b) grazing angle of incidence of sound waves on some vehicle panels and c) shadowing effects resulting from the geometry of the vehicle.

There are many software tools in use today that are implementing the Biot, or complementary, method for the evaluation of foam and fiber materials. The justification of this process is to understand which mechanisms of the noise control material are contributing to the noise reduction and to optimize the material based on its acoustic properties. The disadvantage of this method is that it is quite complex and time consuming to test a material in order to extract the underlying properties that govern the acoustic performance

Automobile sound package design requires that a Statistical Energy Analysis (SEA) model be built during initial stages of any vehicle program. This allows design changes, noise path analysis and optimization of the sound package to be performed before any program design freeze. The 3D model building process becomes a critical element since it involves many weeks of work before the model is ready for sound package definition and analysis. This paper introduces new developments in building 3D SEA models using templates. A new set of tools has been developed to further automate the SEA model building process. These tools should enable the user to develop a full vehicle SEA model within a few days. The productivity improvement gained by reducing model building time will allow for a more effective use of SEA models in the vehicle development cycle.

The complexity of various CAE techniques for modeling NVH phenomena has long remained a difficulty for much of the Automotive Supply community. Complex details of Body Structures and Sound Packages are often not available outside of the OEM community and short program timing provides only a narrow window of opportunity to fine tune CAE models. This paper presents an efficient approach to build full vehicle Statistical Energy Analysis (SEA) models when no CAD/FEA data is available. The resulting model is then used to study the effects of changing the Transmission Loss characteristics of laminated glazing system components.

Develop customized AutoSEA2 Graphical User Interface and related SEA models to predict the acoustical contribution of glass laminates to the interior sound quality.

To predict the vibro-acoustical behavior of a vehicle cockpit module, a statistical energy analysis (SEA) model was developed using AutoSEA2TM. This model was constructed to simulate a complete cockpit, including instrument panel, steering system, HVAC, close-out panels, center console with radio and HVAC controls, instrument cluster, and airbag unit.

A key goal in the effective use of Statistical Energy Analysis (SEA) has been to reduce the number of expert judgments required by an analyst. This could be accomplished by incorporating high level knowledge into software. Another approach used in the SEA community has been to create templates of a particular vehicle that incorporates accumulated technical knowledge.

Engine vibration propagating through its suspension is often responsible for low frequency noise perceived by vehicle occupants. In the design process and at early stage of development, it is useful to have an efficient way of estimating the properties of an engine suspension since these properties directly dictate the engine's structureborne vibration contribution to total noise in the vehicle.

Engine vibration propagating through its suspension is often responsible for low frequency noise perceived by vehicle occupants. In the design process and at early stage of development, it is useful to have an efficient way of estimating the properties of an engine suspension since these properties directly dictate the engine's structureborne vibration contribution to total noise in the vehicle.

Following styling and surface definitions, FEA models for structural subsystems, such as floor and wheelhouse, are constructed early in the vehicle design/development process. At this early stage, there is a need to define appropriate damping treatment and their coverage for different panels in the vehicle.