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Technische Akustik und NVH gehören zu den wichtigsten Indikatoren für Fahrzeugqualität und -verarbeitung. Mit den grundlegenden Veränderungen der Antriebstechnik rücken diese Aspekte daher zunehmend in den Fokus der Automobilforschung und -entwicklung. Fahrzeugarchitekturen, Antriebssysteme und Designgrundsätze werden weltweit wegen der Emissionsgesetzgebungen, die energieeffiziente Fahrzeuge fördern, einer kritischen Betrachtung unterzogen. Schon in sehr naher Zukunft wird die gleiche oder eine höhere NVH-Performance durch Leichtbaustrukturen, kleinere Motoren mit Turbolader oder auch alternative Antriebsstränge erreicht werden müssen. Die internationale Automotive Acoustics Conference bietet hierbei ein wichtiges globales Forum für den Informationsaustausch.



Challenges of achieving better NVH performance for Chinese domestic brands

The NVH performance of a vehicle largely influence customer’s perception and satisfaction of vehicle perceived quality. Vehicle manufacturers have spent significant amount of resources to optimize vehicle NVH to meet the increasing demand of consumers. Recently, the industry has become more aggressive in its lightweighting actions, and the rate of introducing new technology to improve customer’s experience is accelerating. The trend of lightweighting, vehicle electrification, V2X connectivity, intelligence, and autonomous driving as well as eco-design for customer health and environment protection has placed several challenges for vehicle NVH development. First, vehicle weight reduction is a well-known strategy for improving fuel consumption and reducing CO2 emission in vehicles. However, reducing vehicle weight has inevitable consequences for the strength and stiffness of the systems and structures affected. If not implemented carefully, lightweighting strategies can lead to NVH issues that are potentially difficult to remedy because these issues could arise from fundamental design of the vehicle body structure and complex system interactions. Secondly, the combination of lightweighting, electrification, increased demand for advanced driver-assistance system (ADAS), connectivity contents, and faster product cadences has affected overall vehicle cost amortization. This cost amortization limits NVH strategies for noise source design, structural solidity and sound package content. Thirdly, for Chinese car manufacturers, pursuing better NVH performance has become a very important competitive focus in China market to establish brand images and compete with well-known global brands. This paper presents NVH development strategies and techniques to combat these challenges.
Perry P. Gu, Fei Xiong, Hailan Zhao, Xie Kai

Low- and high-frequency NVH CAE – test methods for development of a lightweight sedan design

The Multi Material Lightweight Vehicle (“MMLV”) is a collaborative effort between Ford Motor Company, Magna International and US Department of Energy to design, develop and deliver a 23.3% weight saving over the baseline vehicle, “Vehicle A”, using lightweight materials and manufacturing technologies.
Yuksel Gur, Jian Pan, David A. Wagner

Vibration reduction in automotive applications based on the damping effect of granular material

The improvement in sound quality is an important aspect in the development of automobiles, as it influences the customers comfort and therefore the purchase decision. Furthermore, the legislature has passed several bills that aim at tightening the sound radiation threshold within the next decade. In order to improve the sound emission properties of lightweight designs, extensive research efforts have been devoted to develop sophisticated concepts that achieve an excellent noise reduction at a low mass.
Sebastian Koch, Fabian Duvigneau, Sascha Duczek, Elmar Woschke

State-of-the-art digital road noise cancellation by Harman

Structure-borne road noise dominates the cabin of modern vehicles, especially in the case of electric vehicles (EVs). Several RNC prototype systems based on analogue accelerometers are available in the market. So far the placement of these sensors has been based either on random optimisation methods or on a rule of thumb that at least 3-6 reference signals per wheel are necessary. An improved method for selecting sensor locations and optimising their performance is demonstrated in this paper. The method takes into account suspension and axle locations that are important for NVH/CAE prognosis, TPA and modal analysis of structure-borne road noise.
Nikos Zafeiropoulos, Jürgen Zollner, Vasudev Kandade Rajan

Acura NSX – Hybrid Acoustics, a new carpet concept for meeting stringent performance and weight targets

The NVH development of the all new Acura NSX was a significant challenge. The innovative sports hybrid powertrain allows for a wide range of driving modes each with specific NVH requirements. From highly emotional engine sound to almost silent cruising in pure electric mode. To achieve these high NVH targets without a significant weight penalty required an innovative approach to the NVH treatment package. One key enabler was the carpet system which is based on the Hybrid-Acoustics Technology. Sufficient sound transmission loss performance was combined with a maximum of sound absorption in a lightweight system to meet the targets. This paper shows the theory behind “Hybrid-Acoustics” as well as comparisons of test and simulation results to classical mass based insulations and purely dissipative systems.
Jared Cox, Steve Eich, Andrea Martin, Rolf Balte

Powertrain mounting systems for electric vehicles

Mounting systems for combustion engines are well established for many decades and are constantly being further developed and optimized. Even in the case of increasing demands, such as through downsizing, downspeeding, or lightweight construction on the one hand and increasing comfort demands on the other hand, the fundamental NVH (noise vibration harshness) issues for combustion engines are generally resolved through a wide range of relevant development tools and products.
David Roth, T. Ehrt, C. Bultel, H. Kardoes

Noise radiated by electric motors – simulation process and overview of the optimization approaches

The automotive industry has entered a phase of change due to environmental considerations. Hybrid and electric vehicles have emerged. The vibroacoustic behaviour (knowledge of the source mechanisms and expertise regarding the integration of this source of noise and vibration inside the vehicle structure) of combustion engines is now well controlled. This knowledge cannot be directly transferred to these new vehicles, either hybrid or electric. Therefore, it is necessary to build a new expertise and new tools in order to understand and optimize electric motors and their integration. This paper takes part in this process: the goal is to predict the vibroacoustic characteristics of a motor during the design phase.
Jean-Baptiste Dupont, Henri Saucy

New fuel-saving technologies and NVH refinement of powertrains

The ‘ecological conscience’ of consumer, the CO2 reduction imposed by legislation and the low consumption tax policy adopted by majority of countries, motivate car manufacturers to develop new generation of low CO2 emission cars. The reduction of rolling friction (low resistance pneumatics), of air resistance and of overall mass is the design imperative for low consumption vehicles. Still, the most important reduction of fuel consumption and CO2 emission is to be achieved by new generation of powertrain. This implies different new technologies which can represent a marked impact on NVH-behaviour of engines.
Léon Gavric

Diesel engine control based on structure-borne noise – optimization and adaptation of parameters

Today’s passenger car diesel engines are distinguished by low exhaust emissions and low fuel consumption. In the lower load and engine speed range, however, dominant combustion noises are produced by the higher combustion delay, particularly when the engine is started and warming up. Although multiple pilot injections are used nowadays to reduce irritating combustion noise of this type, they clash with higherpriority exhaust emissions.
Sebastian Schneider, Jan Hendrik Carstens, Jürgen Nobis, Hermann Rottengruber, Clemens Gühmann, Enrico Neumann, Michael Joerres

Combustion mechanical noise breakdown – turbocharger noise identification on a V8 engine

The NVH character of an engine is composed of a mixture of various sources. Some of these have been categorized as combustion related noise and others as mechanical noise. The introduction of modern engine technologies, such as turbocharger, direct injection, etc., often results in additional engine vibrations and radiated noise. Therefore being able to extract specific engine noises is of prime interest in the engine development phase and as well as for engine diagnostic purposes.
Karl Janssens, Fabio Bianciardi, Konstantinos Gryllias, Simone Delvecchio, Claudio Manna

Simulation of exterior noise propagation for the acoustic load estimation of airborne model

The time to market in the automotive industry is constantly decreasing pushing the carmaker companies to increase the efforts in numerical simulations and to decrease the number of prototypes. In the NVH field, the airborne models are widely used for many purposes: from the estimation of the Transmission loss of different parts to the assessment of interior noise due to very complex exterior loads, like aeroacoustic sources. In most cases, the estimation of the exterior load for SEA model is quite complicated and takes a long time to be completed.
The aim of this paper is to present a methodology which is able to forecast the acoustic loads on the exterior surface by exploiting the numerical potentiality of the Fast Multipole Boundary Element Method (FMBEM). In addition, the paper shows a tool that is able to close the gap between the two different methods (FMBEM and SEA), by collecting and processing the data deriving from the FMBEM to be applied to the different panels, which are defined in the SEA method. This is done by a proper averaging – both spatially and in the frequency range – of the pressure for the different panels. The approach is therefore validated by means of a numerical experimental comparison at two different levels: the first one is on the wetted surface, where FMBEM and experimental measurements are compared, while the second one is at the interior cavity level, where the noise level predicted by experimental acoustic loads is compared with the level derived by numerically estimated sources
M. Danti, G. Bartolozzi, M. Meneguzzo, C. Campagna

On the role of simulation in accounting for the design complexity of engine encapsulation

Driven by more and more stringent CO2 [1] and noise emission regulations [2], the need for advanced engineering in the engine bay has significantly increased over the last few years. One of the most effective solutions involves engine encapsulation, which consists in enclosing as much as possible the engine into a capsule-like assembly. On the one hand, this allows retention of heat and reduced CO2 emission, and, on the other hand, decreasing both interior and exterior vehicle noise [3][4].
R. D’Amico, R. Stelzer, J. Grebert, P. Chandler, G. Fossaert

Pass-by noise synthesis from frequency domain exterior acoustic simulations

The evolution of the Pass-by Noise regulation put Automotive OEMs under pressure to reduce the emitted noise from vehicles. To be able to decrease the emitted noise level while meeting other constraints such as weight, space or sound quality, OEMS and their suppliers have to come up with innovative solutions to reduce the different noise sources and study the noise propagation around the vehicle. The experimental study of the acoustic propagation around a complete vehicle during a pass-by noise event occurring late in the development process, the need for methods to investigate solutions to control the acoustic propagation around the vehicle arises. This paper presents a method for predicting a vehicle pass-by noise based on a Finite Element exterior acoustic calculation in the frequency domain. With an approach similar to what is proposed for experimental indoor pass-by noise measurement, the simulated pass-by noise is synthesized from multiple acoustic transfer functions between each noise source and a line of virtual microphones located 7.5m on the side of the vehicle. The method is demonstrated on a car model using Actran commercial software. The contribution from several noise sources to the pass-by noise is evaluated up to 2 kHz and expressed both in terms of sound pressure level and frequency content. Finally the performances and computational times are reported for integration in a design process.
Alexis Talbot, Gregory Lielens

An exploration study of automotive sound package performance in the mid-frequency range

The different sound packages surrounding the interior cavity have a significant contribution to the interior noise performance of a car. The design of the trim for the highfrequency range is well established. However, its design for the mid-frequency range (100-1000 Hz) is more difficult, because of the complex inputs involved, the lack of representative performance metrics and the high computational cost of the simulations. In order to make early decisions for trim design, performance maps, describing the performance metrics of a silencer against the different design variables, are desired for the mid-frequency range.
A framework has been developed to retrieve those maps from an exploration of designs: it constructs those maps based on a surrogate model built on a Gaussian process regression. This surrogate model is iteratively enriched with new designs to increase the accuracy of that model. Each new design consists of a finite element simulation of a sound package in mid-frequencies. In order to gain computation time, it is sped up using a reduced order model which is iteratively improved, until a convergence is achieved on all the metrics of interest.
This paper first summarizes the main aspects of this framework. In a second part, it presents an application of that framework on two typical automotive trim cases under a structure-borne excitation. Both material and geometrical parameters are considered to build performance maps in the mid-frequency range.
Nicolas Schaefer, Bart Bergen, Tomas Keppens, Wim Desmet

The noise reduction potential of lightweight acoustic metamaterials – a numerical and experimental study

Noise reduction of passenger car engines contributes to an improvement of the driving comfort at low and medium speeds. It also helps to meet the acoustic regulations of the legislative authorities that force lower sound pressure levels of the pass-by-noise of cars in the next years. An option to reduce the noise radiated from the engine is the application of a full or a partial engine encapsulation.
Peter Schrader, Fabian Duvigneau, Hermann Rottengruber, Ulrich Gabbert

Vibration damping behavior of flexible polyurethane foams under low and high strain regimes

Polyurethane flexible foam chemistry is a urethane reaction of isocyanate and polyol, to form a soft-like polymer, and a urea reaction of isocyanate and water to provide the blowing agent CO2 which is released during the reaction. The former reaction gives the foam its flexibility, strength and vibration damping properties, while the latter leads to the cellular microstructure and urea groups that phase separate into hard segments and contribute to the load bearing properties of the foam.
Mark Brennan, Martino Dossi, Yueqi Wang, Maarten Moesen, Jan Vandenbroeck

Predicting pass-by noise levels for trucks based on component test bench measurements – by using virtual assembly techniques

The goal of this research is to predict how main noise-causing components contribute to the exterior noise level, without having to physically integrate them in the truck. Road transportation noise is a growing source of concern. Legislations define pass-by noise test procedures according to which vehicles need to be tested. In the European Union, the noise emission limit is set by directive ECE-R51.03 [1]. The ISO standard has recently been updated, defining a more constrained test procedures that better reflect the reality of urban traffic noise [2]. At the European level, a plan has been set to lower noise limits in the next years.
Patrick Corbeels, P. Van de Ponseele, M. Choukri, R. Sinnig, W. Kerres

NVH development strategies for suspensions – challenges and chances by autonomous driving

The safety aspects of autonomous driving, the limiting risks of complex situations or weather conditions and the legal consequences are the present focus of discussions. Once this technique will have become an every days practice in our live, automotive developers will face a new world of customer expectations. After pressing the push bottom “autonomous”, the driver becomes a passenger who is everything else than amused by sporty manner of driving. On a long distance ride, busy with preparing a business presentation or playing games on a tablet with the kids, passengers expect the same comfort of a high speed train.
Andreas Schilp, Hartmut Bathelt

A framework for the sensitivity analysis of transfer paths combining contribution analysis and response modification analysis

The Transfer Path Analysis (TPA) has been thoroughly investigated in the past, and a wide range of different approaches has already been implemented [1]. Each approach has its own properties and possible application cases. These range from a physically complete description of the entire assembly, including contributions and forces, a description of individual components for dynamic sub structuring, to traditional troubleshooting applying operational measurements only. All approaches have their own place in the R&D or production process, and are fully integrated into the processes at most automotive OEMs. The overall goal is to fulfil predefined targets, which might be based on regulations, design decisions or comfort.
Dejan Arsić, Matthias Pohl


Am 11. und 12. Juli 2017 trafen sich mehr als 240 Experten aus 19 Ländern auf der Automotive Acoustics Conference in Zürich/Rüschlikon (Schweiz), um über die Herausforderungen der Automobilindustrie beim Thema Fahrzeugakustik zu diskutieren.
Matthias Heerwagen
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