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Magazine
2014-07-10
Off-highway engines advance beyond Tier 4 With Tier 4 Final/Stage IV needs met, engine OEMs direct their focus and competitive energies toward optimizing competitive solutions. At the same time, they need to keep a weather eye out for future regulations, which many expect. Autonomous vehicle challenges span many fields Many of the challenges faced by military and commercial design teams are similar. Racket busters With a quiet cab at the top of many tractor buyers' wish lists, agricultural equipment manufacturers are pursuing every opportunity possible to shed decibels.
Standard
2014-07-01
This SAE Aerospace Information Report (AIR) provides Nuclear, Biological and Chemical (NBC) protection considerations for environmental control system (ECS) design. It is intended to familiarize the ECS designer with the subject in order to know what information will be required to do an ECS design where NBC protection is a requirement. This is not intended to be a thorough discussion of NBC protection. Such a document would be large and would be classified. Topics of NBC protection that are more pertinent to the ECS designer are discussed in more detail. Those of peripheral interest, but of which the ECS designer should be aware are briefly discussed. Only radiological aspects of nuclear blast are discussed. The term CBR (Chemical, Biological, and Radiological) has been used to contrast with NBC to indicate that only the radiological aspects of a nuclear blast are being discussed. This is actually a more accurate term to describe the subject of this paper, but NBC has become more widely used in the aircraft industry.
Technical Paper
2014-06-30
Bryce Gardner, Tiago Macarios
Abstract Speech transmissibility is a critical factor in the design of public address systems for passenger cabins in trains, aircraft and coaches. Speech transmissibility is primarily affected by the direct field, early low order reflections, and late reflections (reverberation) of the source. The direct and low order reflections are affected by the relative location of speakers and seats as well as the acoustic properties of the reflecting walls. To properly capture these early reflections, measures of speech transmissibility typically require time domain information. However, another important factor for speech transmissibility is background noise due to broadband exterior sources such as a flow noise sources. The background noise is typically modeled with broadband steady state assumptions such as in statistical energy analysis (SEA). This works presents an efficient method for predicting speech transmissiblity by combining ray tracing with SEA. In this method, the direct field and low order reflections are modelled using raytracing, while the reverberant field and background noise are modelled using SEA.
Technical Paper
2014-06-30
Yong Che
Abstract As motor assembly of Battery Electric Vehicle (BEV) replaces engine system of Internal Combustion Engine (ICE) vehicle, interior structure-borne noise induced by road random excitation becomes more prominent under middle and high speed. The research is focused on central driving type BEV. In order to improve interior noise in middle and low frequency range, dynamic load of BEV body must be identified. Consequently the structural noise induced by road excitation is conducted. The limitations of common identification method for dynamic body load are analyzed. The applied several identification methods are proposed for deterministic dynamic load such as engine or motor. Random dynamic load generated by road excitation is different from deterministic dynamic load. The deterministic load identification method cannot be applied to the random load directly. An identification method of dynamic body load for BEV is presented based on power spectrum decomposition. The procedure of BEV body load identification is described.
Technical Paper
2014-06-30
Hiromichi Tsuji, Satoshi Takabayashi, Eiji Takahashi, Hitoshi Murakami, Shinichi Maruyama
A finite element (FE) model of vibro-acoustic coupling analysis, such as a vehicle noise and vibration, is utilized for the improvement of the performance in the vehicle development phase. However, the accuracy of the analysis is not enough for substituting a prototype phase with a digital phase in the product development phases. Therefore, conducting the experiments with the prototype vehicle or the existed production vehicle is still very important for the performance evaluation and the model validation. The vehicle noise transfer function of the road noise performance cannot be evaluated with the existed excitation equipment, such as the 3 or 6 directional electromagnetic shaker. Therefore, this paper proposes new experimental method to measure the road noise vehicle transfer function. This method is based on the reciprocity between the tire contact patch and the driver's ear location. The reaction force sensor of the tire contact patch is newly developed for the reciprocal loud speaker excitation at the passenger ear location.
Technical Paper
2014-06-30
Barbara Neuhierl, David Schroeck, Sivapalan Senthooran, Philippe Moron
Abstract This paper presents an approach to numerically simulate greenhouse windnoise. The term “greenhouse windnoise” here describes the sound transferred to the interior through the glass panels of a series vehicle. Different panels, e.g. the windshield or sideglass, are contributing to the overall noise level. Attached parts as mirrors or wipers are affecting the flow around the vehicle and thus the pressure fluctuations which are acting as loads onto the panels. Especially the wiper influence and the effect of different wiper positions onto the windshield contribution is examined and set in context with the overall noise levels and other contributors. In addition, the effect of different flow yaw angles on the windnoise level in general and the wiper contributions in particular are demonstrated. As computational aeroacoustics requires accurate, highly resolved simulation of transient and compressible flow, a Lattice-Boltzmann approach is used. The noise transmission through the interior is then modeled by statistical energy analysis (SEA), representing the vehicle cabin and the panels excited by the flow.
Technical Paper
2014-06-30
Denis Blanchet, Anton Golota, Nicolas Zerbib, Lassen Mebarek
Abstract 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. This paper discusses in detail these three aspects of wind noise simulation and recommends appropriate methods to deliver required results at the right time based on i) simulation and experimental data availability, ii) design stage and iii) time available to deliver these results. Several simulation methods are used to represent the physical phenomena involved such as CFD, FEM, BEM, FE/SEA Coupled and SEA. Furthermore, a 1D and 2D wavenumber transformation is used to extract key parameters such as the convective and the acoustic component of the turbulent flow from CFD and/or experimental data whenever available.
Technical Paper
2014-06-30
Xiaohong Kuang, Jian Pang, Haiyan Zhang, Liang Yang, Jiang-hua FU
Abstract The paper describes the identification and control methods of turbocharger surge noise. Some parameters, such as temperature, flow quantity, pressure, vibration, turbocharger rpm and noise, are provided to identify surge noise. The advantages and disadvantages for each parameter are analyzed. The paper identifies that some special vehicle interior noise is contributed by turbocharger surge noise by using correlation analysis of the turbocharger inlet temperature, outlet pressure and vehicle internal noise. Spectral filtration analysis shows that the surge noise frequency components are above 1000Hz with wide frequency band. Quarter wave tuner's effective frequency range is found to be consistent with the surge noise frequency band. A panfluter-resonator which is a combination of several special quarter wave tuners is invented to diminish the wide band high frequency noise. After the panfluter-resonator is installed on a turbocharger system, the vehicle interior surge noise is significantly reduced.
Technical Paper
2014-06-30
Alessandro Zanon, Michele De Gennaro, Helmut Kuehnelt, Domenico Caridi, Daniel Langmayr
Abstract In hybrid and electrical vehicles new challenges in meeting the drivers' expectation with regards to acoustic comfort arise. The absence of the internal combustion engine noise enhances the passengers' perception of other noise sources, such as the Heating, Ventilation and Air-Conditioning (HVAC) system. Therefore efficient and reliable numerical models able to predict flow-induced broadband noise have become a major research topic in automotive industry. In this framework, the Zonal LES coupled with the Ffowcs Williams-Hawkings (FWH) acoustic analogy are capable to simulate broadband noise from low speed axial fan. As demonstrated in previous works from the authors, this approach is able to cope with the complexity of the physical phenomena involved (i.e. turbulent noise generation, laminar-to-turbulent transition, etc.), even though the numerical model requires a careful setup of the mesh topology, boundary conditions and simulation parameters. The aim of this article is to provide the scientific community with the latest developments of our research work on numerical modelling of broadband noise from axial fans, focusing on the performance of two different mesh topologies to locate and estimate the noise sources.
Technical Paper
2014-06-30
Dirk Mayer, Jonathan Militzer, Thilo Bein
Abstract The automotive industry is aiming at both reducing the weight of the vehicles while improving a high level of comfort. This causes contradicting requirements for the systems used for noise and vibration control. Thus, active systems are investigated which may enhance the performance of passive noise and vibration control in vehicles without adding excessive weight. In this paper, basic principles for the implementations of those systems with a focus on the control systems are reviewed. Examples from implementations in automotive applications are presented, including control of engine vibrations, structure borne noise transmitted from the road into the passenger compartment and low-frequency chassis vibrations. Based on adaptive filter systems already widely used in active noise control adaptation of the control algorithms to the specific application scenarios are discussed. This includes different configurations for feedforward and feedback control, single- and multichannel control systems and the utilization of different actuator concepts like active mounts, inertial mass actuators and active tuned absorbers, as well as different control sensors like accelerometers and microphones.
Technical Paper
2014-06-30
Gregor Müller, Gottfried Grabner, Michael Wiesenegger, Jörg Jany
The optimal styling of the exterior surface of a vehicle and its suspension system have a direct impact on interior wind noise. Both are determined in early project phases when no hardware prototype is available. Turbulent flows produce both external pressure fluctuations at the vehicle shell, known as hydrodynamic excitation, and sound waves, known as acoustic excitation. Hydrodynamic and acoustic sound sources are evaluated separately and relative to each other in the frequency domain in order to perform evaluations of different body shapes. The technical aim of the presented work is to investigate how acoustic quantities measured at the outside of a vehicle can be used to assess the influence of styling modifications to interior sound pressure level. The methodology is required to be capable of being integrated into the serial development process and therefore be quickly applicable. MAGNA STEYR Engineering has conducted extensive research to develop a method to ensure the best option is selected in the early project stages.
Technical Paper
2014-06-30
Hiromichi Tsuji, Kimihiko Nakano PhD
This paper presents new technique to estimate the projected operational forces, which is the operational forces with respect to the evaluation location, at the connections of the separated passive substructures with reciprocity. Since the transfer path analysis (TPA) is conducted with respect to the evaluation location, the forces for the substructures are, therefore, also required only to estimate the projected operational forces. In order to estimate the forces, the projected inertance matrix, which is the projection of the inertance matrix onto the subspace with respect to the evaluation location, is estimated without measuring it directly. The acceleration responses at the connections of the passive substructure are measured by the excitation at the evaluation location with the reciprocity. The technique decomposes the acceleration responses into the output and input element vectors on the subspace. With those vectors, the projected inertance matrix is constructed. The projected operational forces at the passive substructure can be estimated by the operational accelerations pre-multiplied by the inverted projected inertance matrix.
Technical Paper
2014-06-30
Kasper Steen Andersen, Fuyang Liu
The tailpipe noise from an aftertreatment system must comply with legislation and meet customer expectations. The approach to capture the influence of complicated geometries and the ceramic substrates included in full aftertreatment systems (ATS) is implemented by coupling the 1D analytical solution of the substrates with the 3D FEM solution. The simulations are verified with measurements in a flow acoustic test rig.
Technical Paper
2014-06-30
Augusto Medeiros, Tiago Macarios, Gregorio Azevedo, Bryce Gardner
Abstract Transmission loss (TL) is a common metric for the comparison of the acoustic performance of mufflers. Muffler TL can be computed from a Boundary Element Method (BEM) model. Perforated tube elements are commonly used in automotive muffler applications. These can be modeled with a detailed BEM model that includes each individual hole in the perforated tube. The main drawback with such a straightforward BEM approach is that the discretionary of the perforated surfaces can result in computationally expensive models. The current work uses an approach that is a more computationally-efficient, yet, precise way of modeling complex mufflers that contain perforated surfaces with BEM. In this approach, instead of explicitly modeling the perforations explicitly they are taken into account as equivalent transfer impedances. There are several models in the literature that can be used to develop the transfer impedance model of the perforated surface. This paper investigates how these models can be used in a BEM prediction and also how one needs to be careful in selecting the cases used to evaluate the models.
Technical Paper
2014-06-30
Dennis Bönnen, Djahanchah Bamdad-Soufi, Hannes Steinkilberg, Kwin Abram
Abstract In recent years the automotive industry has been using an increasing number of high powered engines with fewer cylinders, with the goal to reduce weight and fuel consumption and hence to achieve lower CO2 emissions. In the following paper, an overview about the currently existing methods and products within the exhaust development is given which follow automotive lightweight trend. Continuous innovations in new materials, structural design and manufacturing process as well as mastering the integration of the components and modules within the system with a thorough understanding and optimization of the system behavior is enabling the reduction of weight in exhaust system. Another possibility to reduce the weight is the use of additional components such as valves. In the following, a discussion about the different types of valves is presented. These valves can be implemented within the exhaust system in order to bring a constraint in the system and consequently additional acoustic damping.
Technical Paper
2014-06-30
Antti Hynninen, Mats Abom
Abstract The after treatment devices (ATD) used in internal combustion engine (IC-engine) exhaust systems are mainly designed with emphasis on emission control, i.e. chemical efficiency, while paying less attention to the acoustic performance. In automotive applications, the duct diameters are so small that studying the acoustic wave propagation only in the plane wave frequency range is usually sufficient. In the case of medium speed IC-engines, used for example in power plants and ships, the three dimensional acoustic phenomena must also be taken into account. The main elements of the medium speed IC-engine ATD are the selective catalytic reducer (SCR) and oxidation catalyst (OC), which are based on a large amount of coated channels, i.e. the substrates. The number and type of the substrates depends not only on the regional environment legislations but also on the engine type. In this study the acoustic attenuation of a medium speed IC-engine ATD is simulated and the results are compared with measurements.
Technical Paper
2014-06-30
Ennes Sarradj, Thomas Geyer, Christoph Jobusch, Sebastian Kießling, Alexander Neefe
Abstract The development of energy-efficient and lightweight vehicles is a major challenge for researchers and engineers in the automotive industry, with one solution being the use of micro gas turbines in serial hybrid vehicles. Among other advantages, the use of a micro gas turbine instead of a reciprocating engine enables a high reliability and low emissions. What makes the concept of using a gas turbine even more interesting are its special NVH characteristics, which are quite different from those of a reciprocating engine. Besides the fact that a gas turbine in general produces less noise and vibration than a diesel engine of the same power, the characteristic noise spectrum is also very different. In this paper, the noise characteristics of a micro gas turbine are compared to those typical for a common reciprocating engine and the sources of the noise are considered. The data that form the basis for these analyses were obtained using measurements on a 70 kW micro gas turbine that is designed to be used in a serial hybrid concept for buses.
Technical Paper
2014-06-30
Michael Klanner, Mathias Mair, Franz Diwoky, Oszkar Biro, Katrin Ellermann
Abstract The noise vibration and harshness (NVH) simulation of electric machines becomes increasingly important due to the use of electric machines in vehicles. This paper describes a method to reduce the calculation time and required memory of the finite element NVH simulation of electrical machines. The stator of a synchronous electrical machine is modeled as a two-dimensional problem to reduce investigation effort. The electromagnetic forces acting on the stator are determined by FE-simulation in advance. Since these forces need to be transferred from the electromagnetic model to the structural model, a coupling algorithm is necessary. In order to reduce the number of nodes, which are involved in the coupling between the electromagnetic and structural model, multipoint constraints (MPC) are used to connect several coupling nodes to one new coupling node. For the definition of the new coupling nodes, the acting load is analyzed with a 2D-FFT. After the coupling with MPCs, forces are only acting on the newly defined coupling nodes.
Technical Paper
2014-06-30
Yuan feng Xia, Jian Pang, Chengtai Hu, Cui Zhou, Cong Wu
Abstract The paper analyzes the characteristics of driveline torsional vibration of a RWD vehicle and provides the control methods of transmission rattle noise caused by the system torsional resonances. A driveline dynamic model of the RWD vehicle is established by multi-body dynamic method. The natural frequencies and modal shapes are calculated for each gear position and torsional vibration responses are predicted by forced vibration analysis. The system sensitivity and DOE are analyzed based on the parameterized stiffness, inertia and damping. The 2nd and 3rd order modal results show that the transmission shaft possesses the maximum amplitudes and its corresponding modal frequencies vary with different gear position. The sensitivity analysis results show that the system torsional vibration is significantly reduced by reducing clutch stiffness, increasing propeller shaft stiffness, raising half shaft stiffness, increasing the input shaft inertia and increasing the clutch damping. The DOE analysis results show that the clutch stiffness, propeller shaft stiffness, and the inertia of axle pinion shaft and transmission input shaft play an important role in reducing torsional vibration of the transmission gear shafts.
Technical Paper
2014-06-30
Gregor Tanner, David J. Chappell, Dominik Löchel, Niels Søndergaard
Abstract Modelling the vibro-acoustic properties of mechanical built-up structures is a challenging task, especially in the mid to high frequency regime, even with the computational resources available today. Standard modelling tools for complex vehicle parts include finite and boundary element methods (FEM and BEM), as well as Multi-Body Simulations (MBS). These methods are, however, robust only in the low frequency regime. In particular, FEM is not scalable to higher frequencies due to the prohibitive increase in model size. We have recently developed a new method called Discrete Flow Mapping (DFM), which extends existing high frequency methods, such as Statistical Energy Analysis or the so-called Dynamical Energy Analysis (DEA), to work on meshed structures. It provides for the first time detailed spatial information about the vibrational energy of a whole built-up structure of arbitrary complexity in this frequency range. The response of small-scale features and coupling coefficients between sub-components are obtained through local FEM models integrated in the global DFM treatment.
Technical Paper
2014-06-30
Ze Zhou, Jonathan Jacqmot, Gai Vo Thi, ChanHee Jeong, Kang-Duck Ih
Abstract The NVH study of trimmed vehicle body is essential in improving the passenger comfort and optimizing the vehicle weight. Efficient modal finite-element approaches are widely used in the automotive industry for investigating the frequency response of large vibro-acoustic systems involving a body structure coupled to an acoustic cavity. In order to accurately account for the localized and frequency-dependant damping mechanism of the trim components, a direct physical approach is however preferred. Thus, a hybrid modal-physical approach combines both efficiency and accuracy for large trimmed body analysis. Dynamic loads and exterior acoustic loads can then be applied on the trimmed body model in order to evaluate the transfer functions between these loads and the acoustic response in the car compartment. The scenario study of installing different trim components into the vehicle provides information on the acoustic absorption and dynamic damping with regard to added vehicle weight by the trim.
Technical Paper
2014-06-30
Tom Knechten, Christophe Coster, Peter Van der Linden
Abstract The need for more durable mobility has led to a rapid introduction of new electric systems on vehicles. The result of the application of electrified drivelines is a shift in noise energy from the low mid frequencies towards the upper end of the audible range. Following this, the need for higher frequency noise control and accurate measurement has grown. The measurement of the acoustic transfer or vehicle body isolation at higher frequencies poses a challenge for the diffraction, source level and omni-directionality. This paper shows an improved method that increases the accuracy of acoustic transfer function measurements from the components to the ear at high frequencies. A simulation model based on the Boundary Element Methods(BEM) has been made to analyze higher frequency behavior of noise sources during reciprocal measurements up to 12 kHz. Some dedicated hardware was developed in combination with a new process. The simulation results have been validated by experimental test results, and application tests have been done on a full vehicle.
Technical Paper
2014-06-30
Jean-Francois Rondeau, Ludovic Dejaeger, Antoine Guellec, Arnaud Caillet, Lars Bischoff
Abstract Strategies for weight reduction have driven the noise treatment advanced developments with a great success considering the already mastered weight decreases observed in the last years in the automotive industry. This is typically the case for all soft trims parts. In the early 2010's a typical european B-segment car soft trims weights indeed 30 to 40% less than in the early 2000's years. The main driver behind such a gap has been to combine insulation and absorption properties on a single part while increasing the number of layers. This product-process evolution was conducted using a significant improvement in the simulation capacities. In that sense, several studies presenting very good correlation results between Transmission Loss measurements and finite elements simulations on dashboard or floor insulators were presented. One may consider that those kinds of parts have already achieved a considerable improvement in performance. But the challenge of weight reduction continues due to up-coming CO2 emissions regulations.
Technical Paper
2014-06-30
Gilles Nghiem, Shanjin Wang
Abstract The vehicle pass-by noise regulation will change in the near future and noise limits will be lowered significantly. This evolution will require improvement of engine's sound radiation. On the other hand, under the current pressure for fuel economy, future engines will be more and more lightened, and this will have negative impact on engine's sound emission. Therefore, the requirements related to the new pass-by noise regulation should be taken into account in the design of new powertrains, and in some cases, innovative solutions must be developed in order to improve the level of noise of the engine while reducing the masse of the engine. One effective way is to optimize the design of some key engine parts, such as crankshaft and engine bottom structure. Original approaches had been conducted and showed how much these engine parts can affect powertrain radiated noise, and in addition to find a quantitative relationship between crankshaft stiffness and powertrain radiated noise.
Technical Paper
2014-06-30
Gregor Koners, Ralf Lehmann
Abstract Low interior noise levels in combination with a comfortable sound is an important task for passenger cars. Due to the reduction of many noise sources over the last decades, nowadays tire-road noise has become one of the dominant sources for the interior noise. Especially for manufactures of luxury cars, the reduction of tire-road noise is a big challenge and therefore a central part of NVH development. The knowledge of the noise transmission behavior based on the characteristics of the relevant sources is a fundamental of a modern NVH - development process. For tire-road noise the source characteristics can be described by wheel forces and radiated airborne noise. In combination with the related vehicle transfer functions it is possible to describe the noise transmission behavior in detail. A method for estimating wheel forces and radiated airborne noise is presented. The method is based on TPA (= Transfer Path Analysis) via matrix inversion and involves the measurement of the vehicle transfer functions.
Technical Paper
2014-06-30
Daniel Fernandez Comesana, Emiel Tijs, Daewoon Kim
Abstract For (benchmark) tests it is not only useful to study the acoustic performance of the whole vehicle, but also to assess separate components such as the engine. Reflections inside the engine bay bias the acoustic radiation estimated with sound pressure based solutions. Consequently, most current methods require dismounting the engine from the car and installing it in an anechoic room to measure the sound emitted. However, this process is laborious and hard to perform. In this paper, two particle velocity based methods are proposed to characterize the sound radiated from an engine while it is still installed in the car. Particle velocity sensors are much less affected by reflections than sound pressure microphones when the measurements are performed near a radiating surface due to the particle velocity's vector nature, intrinsic dependency upon surface displacement and directivity of the sensor. Therefore, the engine does not have to be disassembled, which saves time and money. An array of special high temperature particle velocity probes is used to measure the radiation simultaneously at many positions near the engine of a compact class car.
Technical Paper
2014-06-30
Roland Sottek, Bernd Philippen
Abstract In the engine development process, the ability to judge NVH comfort as early as possible is a great benefit. The prediction of engine noise on the basis of a prototype engine without the need to install it in a real car significantly speeds up the development process and leads to a cost reduction, as prototype modifications can be evaluated faster. Meaningful predictions of the perceived NVH comfort cannot be achieved just by comparing order levels, but require listening to an auralization of the engine noise at the driver's position. With the methods of Transfer Path Analysis and Synthesis (TPA/TPS) a prototype engine can be virtually installed in a car using test-bench data. The interior noise can be estimated by combining source signals containing near-field airborne noise radiation and mount forces with transfer functions describing the transmission to the target position in the cabin. Even the transfer functions of a predecessor car could be used if the new car body is not yet available.
Technical Paper
2014-06-30
Ki-Sang Chae, Seung Hwan Lim, Ji Woo Yoo, Seok-Gil Hong
Abstract Dash panel is the most important path of structure-borne and air-borne interior noise for engine-driven vehicles. Reinforcements, which are added to dash panel, are mainly designed in order to suppress the structure-borne noise contribution from the dash panel. However, the effects of dash reinforcements do not seem clear in the viewpoint of air-borne noise. In this paper, the insulation performance of a dash structure with spot-welded reinforcements is studied through several STL (Sound Transmission Loss) tests and STL simulations. The results of this study could be utilized for increasing the sound insulation performance of vehicle body structure.
Technical Paper
2014-06-30
Rainer Stelzer, Theophane Courtois, Ki-Sang Chae, Daewon SEO, Seok-Gil Hong
Abstract The assessment of the Transmission Loss (TL) of vehicle components at Low-Mid Frequencies generally raises difficulties associated to the physical mechanisms of the noise transmission through the automotive panel. As far as testing is concerned, it is common in the automotive industry to perform double room TL measurements of component baffled cut-outs, while numerical methods are rather applied when prototype or hardware variants are not available. Indeed, in the context of recent efforts for reduction of vehicle prototypes, the use of simulation is constantly challenged to deliver reliable means of decision during virtual design phase. While the Transfer matrix method is commonly and conveniently used at Mid-High frequencies for the calculation of a trimmed panel, the simulation of energy transfer at low frequencies must take into account modal interactions between the vehicle component and the acoustic environment. After providing a brief review of the established approaches for TL simulation at LF, the article will present a new FE methodology for TL simulation and introduce the advantages of “in-situ” TL simulations by means of fluid-structure FE calculation.
Technical Paper
2014-06-30
Matteo Kirchner, Eugene Nijman
Abstract Automotive industry is becoming more and more interested in assessing the noise of electric motors, since their integration in many types of road vehicles is rapidly growing in a market oriented to hybridization and electrification. The acoustic characterization of an electric motor is often being performed numerically, having as consequence the fact that the investigation is confined to one specific model belonging to one particular type of motor. This paper proposes an experimental airborne sound characterization methodology, suitable for any type of cylindrical source, based on a set of data acquired following a cylindrical Nearfield Acoustical Holography (NAH) scheme. Such an approach allows the evaluation of sound intensity, as well as pressure level and particle velocity. Practical aspects of cylindrical holography such as positioning error, background noise, hologram distance, spatial sampling, measurement aperture are investigated and discussed with the aid of numerical examples.
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