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Viewing 151 to 180 of 9066
2015-06-15
Technical Paper
2015-01-2246
Kurt Veggeberg, Mike Denton
Abstract This is an overview of the development of a portable, real-time acoustic beamformer based on FPGA (Field Programmable Gate Arrays) and digital microphones for noise source identification. Microphone arrays can be a useful tool in identifying noise sources and give designers an image of noise distribution. The beamforming algorithm is a classic and efficient algorithm for signal processing of microphone arrays and is the core of many microphone array systems. High-speed real-time beamforming has not been implemented much in a portable instrument because it requires large computational resources. Utilizing a beamforming algorithm running on a Field Programmable Gate Array (FPGA), this camera is able to detect and locate both stationary and moving noise sources. A high-resolution optical camera located in the middle of the device records images at a rate of 25 frames per second.
2015-06-15
Technical Paper
2015-01-2302
Yuksel Gur, Jian Pan, David Wagner
Lightweighting of vehicle panels enclosing vehicle cabin causes NVH degradation since engine, road, and wind noise acoustic sources propagate to the vehicle interior through these panels. In order to reduce this NVH degradation, there is a need to develop new NVH sound package materials and designs for use in lightweight vehicle design. Statistical Energy Analysis (SEA) model can be an effective CAE design tool to develop NVH sound packages for use in lightweight vehicle design. Using SEA can help engineers recover the NVH deficiency created due to sheet metal lightweighting actions. Full vehicle SEA model was developed to evaluate the high frequency NVH performance of “Vehicle A” in the frequency range from 200 Hz to 10 kHz. This correlated SEA model was used for the vehicle sound package optimization studies. Full vehicle level NVH laboratory tests for engine and tire patch noise reduction were also conducted to demonstrate the performance of sound package designs on “Vehicle A”.
2015-06-15
Technical Paper
2015-01-2300
Robert Fiedler, Chadwyck Musser, Petr Cuchý
Abstract This paper addresses the NVH design of a light rail vehicle whose maximum allowable interior SPL levels at certain speeds are regulated and may vary between countries, states, and cities. The objective of this study was to predict sound pressure levels (SPL) at several interior locations across a wide range of frequencies and estimate if the current design configuration will meet the noise level limits. Statistical Energy Analysis (SEA) was used to predict interior SPL and to understand and rank the various noise contribution paths and give a better understanding of the physics of transmission and what types of design changes are most effective to reduce the overall interior SPL to meet targets. A typical light rail vehicle is composed of a frame-like structure covered by lightweight panels and with interior panels that are increasingly made from composites, sandwich, laminated, or honeycomb materials or extruded panels.
2015-06-15
Technical Paper
2015-01-2313
Bryce Gardner, Abderrazak Mejdi, Chadwyck Musser, Sébastien Chaigne, Tiago De Campos Macarios
Abstract Flow strongly affects the propagation of acoustics wave transmission within a duct and this must be addressed by the vibro-acoustic modelling of duct systems subject to non-uniform flow. Flow impacts both the effective sound propagation speed in a duct and refracts the sound towards or away from the duct walls depending on whether the acoustic waves are propagating in the direction of the flow or against the flow. Accurate modeling of the acoustic propagation within a duct is crucial for design and “tuning” of muffler systems that need to strongly attenuate narrowband acoustic sources from the engine. Muffler systems that may avoid matching acoustic resonances to engine narrowband sources when no flow is present may experience shifting of resonances to frequencies that match engine sources and cause problems when the flow during a real operating condition is present.
2015-06-15
Technical Paper
2015-01-2350
Jiantie Zhen, Scott Fredrickson
Abstract Off-highway machine mounting system isolation, especially the cab mounting system, significantly affects the operator comfort by providing damping to the harsh inputs and isolating the structure-borne energy from traveling into the cab. Mounting system isolation performance is decided not only by the isolation component, but also the mounting bracket structure, and should be treated as a system. This paper gives a review of how the mounting system isolates structural energy and the effect of the bracket structure stiffness to the mounting system isolation performance.
2015-06-15
Technical Paper
2015-01-2204
Michael Funderburg
The ability of various plasticizers to impact the vibration damping properties of polyvinyl chloride (PVC) plastisols was investigated. A material must have good viscoelastic properties in order for it to be an effective vibration damper. However, it is evident that not all viscoelastic materials are good vibration dampers. Consider flexible (plasticized) PVC, for example. PVC formulations demonstrating the same glass transition temperature may have widely different damping capabilities. This presentation will show that the type of plasticizer substantially impacts the damping ability of the final PVC composite. Initially, flexible PVC formulations with varied plasticizers were screened via dynamic mechanical thermal analysis (DMTA) to determine which ones would likely have good damping properties. Formulations which exhibited promising results with DMTA were then tested via an Oberst bar damping test (SAE J1637).
2015-06-15
Technical Paper
2015-01-2341
Marc Ingelmann, Holger Bickelmann
Abstract Microcellular Polyurethane is for many applications an alternative material to compact elastomers like rubber, with many beneficial and unique properties. Thus relates to the progressive load-deflection-characteristic, the amplitude-selective-damping, the good acoustic isolation and the high durability. The dynamic and static performance of the material, combined with the ability to work in limited packages, makes the usage beneficial for many automotive/transportation applications. The amplitude selective damping fits to the automotive requirements: small amplitudes are generating a low damping of the material; high amplitudes are increasing the damping. Translated in the characteristic for bushings and mounts, this results in a very good isolation for acoustic effects (e.g. rough road conditions) and a very good damping of vibrations (e.g. part- or system resonances).
2015-06-15
Technical Paper
2015-01-2202
Catheryn Jackson, Justin E. Gimbal, Dhara Metla
Abstract Over the past decade damping materials have contributed major improvements to passenger comfort. Noise Vibration and Harshness (NVH) engineers have further shaped material specifications to reflect key targeted properties that improve vehicle design. The specified damping material is then applied to the formed surfaces of the vehicle body to provide optimal performance and achieve the required results. This paper describes how liquid dampers have advanced to meet increased performance requirements through improved loss modulus of the final coating. Data generated by dynamic mechanical analysis shows that this viscoelastic behavior is what drives the performance in damping materials. Through the correlation of loss moduli to damping performance of Oberst bars, the mechanism can be further quantified and explained.
2015-06-15
Journal Article
2015-01-2349
Jiantie Zhen, David Copley, Niranjan Londhe, Scott Fredrickson
Abstract Structure-borne inputs to hybrid FEA/SEA models could have significant effects on the model prediction accuracy. The purpose of this work was to obtain the structure-borne noise (SBN) inputs using a simplified transfer path analysis (TPA) and identify the significance of the structure-borne and airborne contributions to the spectator sound power of an engine with enclosure for future modeling references. Force inputs to the enclosure from the engine were obtained and used as inputs to a hybrid engine enclosure model for sound prediction.
2015-06-15
Journal Article
2015-01-2203
Maaz Farooqui, Tamer Elnady, Ragnar Glav, Tony Karlsson
Abstract A novel porous metallic foam has been studied in this work. This composite material is a mixture of resin and hollow spheres. It is lightweight, highly resistive to contamination and heat, and is capable of providing similar or better sound absorption compared to the conventional porous absorbers, but with a robust and less degradable properties. Several configurations of the material have been tested inside an expansion chamber with spatially periodic area changes. Bragg scattering was observed in some configurations with certain lattice constants. The acoustic properties of this material have been characterized from the measurement of the two-port matrix across a cylindrical sample. The complex density and speed of sound can be extracted from the transfer matrix using an optimization technique. Several models were developed to validate the effect of this metallic foam using Finite Elements and the Two-port Theory.
2015-06-15
Journal Article
2015-01-2173
Srikumar C Gopalakrishnan, Teik Lim
Abstract Modeling of elastohydrodynamic lubrication phenomena for the spiral bevel gears is performed in the present study. The damping and the friction coefficient generated from the lubricated contact area will have profound effects on the dynamics of spiral bevel gears. Thus the damping value generated from this friction model will be time varying. This makes the use of constant and empirical damping value in the dynamics of spiral bevel gears questionable. The input geometric and kinematic data required for the elastohydrodynamic lubrication (EHL) simulations are obtained using Tooth Contact Analysis. A full numerical elastohydrodynamic lubrication simulations are carried out using asymmetric integrated control volume (AICV) algorithm to compute the contact pressures. The fast Fourier transform is used to calculate the elastic deformations on the gear surfaces due to contact load.
2015-06-15
Journal Article
2015-01-2178
Mohamed El Morsy, Gabriela Achtenova
Abstract When localized fault occurs in a bearing, the periodic impulsive feature of the vibration signal appears in time domain and the corresponding Bearing Characteristic Frequencies (BCFs) emerge in frequency domain. The common technique of Fast Fourier Transforms (FFT) and Envelope Detection (ED) are always used to identify faults occurring at the BCFs. In the early stage of bearing failures, the BCFs contain very little energy and are often overwhelmed by noise and higher-level macro-structural vibrations. In order to extract the weak fault information submerged in strong background noise of the gearbox vibration signal, an effective signal processing method would be necessary to remove such corrupting noise and interference. Optimal Morlet Wavelet Filter and Envelope Detection (ED) are applied in this paper.
2015-06-15
Journal Article
2015-01-2182
Yawen Wang, Junyi Yang, Xuan Li, Guohua Sun, Teik Lim
Abstract Due to the design of lightweight, high speed driveline system, the coupled bending and torsional vibration and rotordynamics must be considered to predict vibratory responses more realistically. In the current analysis, a lumped parameter model of the propeller shaft is developed with Timoshenko beam elements, which includes the effect of rotary inertia and shear deformation. The propeller shaft model is then coupled with a hypoid gear pair representation using the component mode synthesis approach. In the proposed formulation, the gyroscopic effect of both the gear and propeller shaft is considered. The simulation results show that the interaction between gear gyroscopic effect and propeller shaft bending flexibility has considerable influence on the gear dynamic mesh responses around bending resonances, whereas the torsional modes still dominate in the overall frequency spectrum.
2015-06-15
Journal Article
2015-01-2188
Zhaohui Sun, Glen Steyer, Chih Hung Chung, Gregory Kopp
Abstract This paper discusses approaches to properly design aluminum axles for optimized NVH characteristics. By effectively using well established and validated FEA and other CAE tools, key factors that are particularly associated with aluminum axles are analyzed and discussed. These key factors include carrier geometry optimization, bearing optimization, gear design and development, and driveline system dynamics design and integration. Examples are provided to illustrate the level of contribution from each main factor as well as their design space and limitations. Results show that an aluminum axle can be properly engineered to achieve robust NVH performances in terms of operating temperature and axle loads.
2015-06-15
Journal Article
2015-01-2179
Laihang Li, Rajendra Singh
Abstract The transient vibration phenomenon in a vehicle powertrain system during the start-up (or shut-down) process is studied with focus on the development and experimental validation of the nonlinear powertrain models. First, a new nonlinear four-degree-of-freedom torsional powertrain model for this transient event, under instantaneous flywheel motion input, is developed and then validated with a vehicle start-up experiment. Second, the interactions between the clutch damper and the transmission transients are established via transient metrics. Third, a single-degree-of-freedom nonlinear model, focusing on the multi-staged clutch damper, is developed and its utility is then verified.
2015-06-15
Journal Article
2015-01-2180
Almahdi Saleh, Michael Krak, Jason Dreyer, Rajendra Singh
Abstract This study examines clutch-damper subsystem dynamics under transient excitation and validates predictions using a new laboratory experiment (which is the subject of a companion paper). The proposed models include multi-staged stiffness and hysteresis elements as well as spline nonlinearities. Several example cases such as two high (or low) hysteresis clutches in series with a pre-damper are considered. First, detailed multi-degree of freedom nonlinear models are constructed, and their time domain predictions are validated by analogous measurements. Second, key damping sources that affect transient events are identified and appropriate models or parameters are selected or justified. Finally, torque impulses are evaluated using metrics, and their effects on driveline dynamics are quantified. Dynamic interactions between clutch-damper and spline backlash nonlinearities are briefly discussed.
2015-06-15
Journal Article
2015-01-2199
Rui Cao, J Stuart Bolton
Abstract Experimental measurements of tire tread band vibration have provided direct evidence that higher order structural-acoustic modes exist in tires, not just the well-known fundamental acoustical mode. These modes display both circumferential and radial pressure variations within the tire's air cavity. The theory governing these modes has thus been investigated. A brief recapitulation of the previously-presented coupled structural-acoustical model based on a tensioned string approach will be given, and then an improved tire-acoustical model with a ring-like shape will be introduced. In the latter model, the effects of flexural and circumferential stiffness are considered. This improved model accounts for propagating in-plane vibration in addition to the essentially structure-borne flexural wave and the essentially airborne longitudinal wave accounted for in the previous model. The longitudinal structure-borne wave “cuts on” at the tire's circumferential ring frequency.
2015-06-15
Journal Article
2015-01-2193
Masami Matsubara, Daiki Tajiri, Makoto Horiuchi, Shozo Kawamura
Abstract One of the elements of tire stiffness is sidewall stiffness. This stiffness, which influences tire vibration characteristics, is also an important design parameter for carrying the vehicle body. Tire is one of pressure vessels and inflation pressure is dominant in sidewall stiffness. Thus, tire sidewall stiffness is decided from the tension of inflation pressure and the structural dynamic, including the properties of the rubber material. To reveal the dynamic characteristics of tire sidewall stiffness, this study describes differences in stiffness due to inflation pressure. It can be expected that variation of inflation pressure is monitored from the axle vibration response during vehicle traveling in the future. That is because the relationship of the vibration characteristics and the inflation pressure of tire are derived by sidewall stiffness. First, we derive a formula for sidewall stiffness based on the structural dynamics of Akasaka's theory.
2015-06-15
Journal Article
2015-01-2218
Shuguang Zuo, Jun Zhang, Xudong Wu, Jiajie Hu, Guo Long
Abstract Blower is one of the main noise sources of fuel cell vehicle. In this paper, a narrowband active noise control (ANC) model is established based on adaptive notch filter (ANF) to control the high-frequency noise produced by the blower. Under transient conditions, in order to reduce the frequency mismatch (FM) of ANC for blower, a new Frequency Mismatch Filtered-Error Least Mean Square algorithm (FM-FELMS) is proposed to attenuate blower noise under transient conditions. According to the theoretical analysis and simulation, the proposed algorithm has an excellent noise reduction performance at relatively high blower speed. While for the low speed working condition, the Normalized Least Mean Square (NLMS) algorithm is applied to attenuate noise. The two algorithms could be jointly utilized to control the blower noise actively.
2015-06-15
Journal Article
2015-01-2215
Thomas L. Lago
Abstract How to decrease noise and vibration exposure has been of interest for many years. Empirical data have indicated that too high dose values can create multiple problems to a human body - often severe. Some years back, the European Machinery Directive has increased the responsibility for manufacturers and employers to make sure limits are complying with legislation. Classical technology often consists of passive solutions aiming at trying to cut back on noise and vibration levels. For low frequency, these methods are often lacking the needed performance especially if weight should be considered at the same time. A smart combination of passive and active techniques can make a real difference. Today, with possibilities for low cost and embedded electronics and the rapid development of new actuators, a vast range of applications are possible for this combined combat approach, with a financial advantage as well.
2015-06-15
Journal Article
2015-01-2224
Yong Xu
Abstract An adaptive feed-forward active control system for improving the sound quality of vehicle engine noise is presented in this paper. Based on the narrow-band and periodic properties of engine noise, an artificial waveform, which was synthesized with sinusoidal components at the fundamental frequency of the engine noise and its harmonics, was adopted as the reference signal. Then these primary noise components were canceled via an adaptive notch filter bank, the coefficients of which were updated using the FXLMS algorithm. The core of the designed system is a new algorithm for improving the quality characteristics of the residual noise by adjusting the gain values of the noise component at each reference frequency. The feasibility and advantages of the designed system were validated through both simulation and practical vehicle tests.
2015-06-15
Journal Article
2015-01-2220
Ji Xu, Guohua Sun, Tao Feng, Mingfeng Li, Teik Lim
Abstract This paper describes an active sound tuning (AST) system for vehicle powertrain response. Instead of simply aiming to attenuate cabin interior noise, AST system is capable of reshaping the powertrain response based on predetermined vehicle sound quality criteria. However, conventional AST systems cannot yield a balanced result over the broad frequency range when applied to powertrain noise. It is due to the fact that existing systems are typically configured with the filtered-x least mean square (FXLMS) algorithm or its modified versions, which has inherent frequency dependent convergence behavior due to large dynamic range of secondary path (the electro-acoustic path from the control speaker to the error microphone). Therefore, fast convergence can only be reached at the resonant frequencies.
2015-06-15
Journal Article
2015-01-2222
Nikos Zafeiropoulos, Marco Ballatore, Andy Moorhouse, Andy Mackay
Abstract Axle forces from tire-road interaction can excite different structural resonances of the vehicle hence a high number of sensors is required for observing and separating all the vibrations dynamics that are coherent with the cabin noise. Feed-forward road noise control strategies adopted so far rely mainly on capturing these dynamics and thus the number of sensors constitutes one major limitation of this approach. Therefore there is a necessity for reducing the number of sensors without degrading the performance of an ANC system. In the past coherence function analysis has been found to be a useful tool for optimizing the sensor location. In this case coherence function mapping was performed between an array of vibration sensors and the headrest microphones in order to identify the locations on the structure that are highly correlated with road noise bands in the compartment.
2015-06-15
Journal Article
2015-01-2261
Joseph Plattenburg, Jason Dreyer, Rajendra Singh
Abstract Combined active and passive damping is a recent trend that can be an effective solution to challenging NVH problems, especially for lightweight vehicle components that demand advanced noise and vibration treatments. Compact patches are of particular interest due to their small size and cost, however, improved modeling techniques are needed at the design stage for such methods. This paper presents a refined modeling procedure for side-by-side active and passive damping patches applied to thin, plate-like, powertrain casing structures. As an example, a plate with fixed boundaries is modeled as this is representative of real-life transmission covers which often require damping treatments. The proposed model is then utilized to examine several cases of active and passive patch location, and vibration reduction is determined in terms of insertion loss for each case.
2015-06-15
Journal Article
2015-01-2255
Jun Kokaji, Masashi Komada, Masayuki Takei, Masaya Takeda
Abstract Although idling vibration is usually caused by 1st order of engine combustion force, other engine forces also occur at frequencies lower than the 1st order of combustion (called low frequency idling vibration in this paper). The drive-line of the Toyota Hybrid System II (THS II) has different torsional vibration characteristics compared to a conventional gasoline engine vehicle with an automatic transmission. Nonlinear characteristics caused by the state of backlash of pinions and splines influence changes in the torsional resonance frequency. The torsional resonance frequency of the drive-line can be controlled utilizing the hybrid system controls of the THS II.
2015-06-15
Journal Article
2015-01-2252
Haixin Dai, Weikang Jiang, Yuanyi Huang
Abstract Engine mounts play important roles in interior noise of automobiles. Decoupling optimal design of mounts has been researched for long, but reducing vibration power into body transmitted from engine can be a more intuitive way to improve NVH performance. Some approaches for minimizing transfer power through engine mounts based on finite element model were reported, whose disadvantages are lack of data and inaccuracy at high frequency in some cases. To get an analytic formula of transmitted power, a model considering coupled vibration between the body and the engine is presented here. An admittance function matrix is used to describe the dynamic relationship between the mounting points on the body side. Based on this admittance matrix measured on the full vehicle, and excitation forces identified with acceleration data measured on all mounts, the vibration equation of the coupled model can be established by using Lagrange's methodology.
2015-06-15
Journal Article
2015-01-2275
Manfred Koberstein, Zhengyu Liu, Curtis Jones, Suhas Venkatappa
Abstract In the thermal expansion valve (TXV) refrigerant system, transient high-pitched whistle around 6.18 kHz is often perceived following air-conditioning (A/C) compressor engagements when driving at higher vehicle speed or during vehicle acceleration, especially when system equipped with the high-efficiency compressor or variable displacement compressor. The objectives of this paper are to conduct the noise source identification, investigate the key factors affecting the whistle excitation, and understand the mechanism of the whistle generation. The mechanism is hypothesized that the whistle is generated from the flow/acoustic excitation of the turbulent flow past the shallow cavity, reinforced by the acoustic/structural coupling between the tube structural and the transverse acoustic modes, and then transmitted to evaporator. To verify the mechanism, the transverse acoustic mode frequency is calculated and it is coincided to the one from measurement.
2015-06-15
Journal Article
2015-01-2276
Zhengyu Liu, Donald Wozniak, Manfred Koberstein, Curtis Jones, Jan Xu, Suhas Venkatappa
Abstract Refrigerant flow-induced gurgling noise is perceived in automotive refrigerant systems. In this study, the condition of the gurgling generation is investigated at the vehicle level and the fundamental root cause is identified as the two-phase refrigerant flow entering the TXV for system equipped with variable displacement compressors. By conducting literature reviews, the acoustic characteristics of the flow patterns and the parameters affecting the flow regimes in horizontal and vertical tubes are summarized. Then the gurgling mechanism is explained as the intermittent flow is developed at the evaporator inlet. In the end, the improved and feasible design for avoiding the intermittent flow (slug, plug or churn flow) or minimizing its formation is proposed and verified in refrigerant subsystem (RSS) level. Finally, the guidelines for the attenuation and suppression of the gurgle are provided.
2015-06-15
Journal Article
2015-01-2285
Arne Nykänen, David Lennström, Roger Johnsson
Abstract Subjects who are well aware of what to judge commonly yield more consistent results in laboratory listening tests. This awareness may be raised by explicit instructions and training. However, too explicit instructions or use of only trained subjects may direct experiment results in an undesired way. An alternative is to give fairly open instructions to untrained subjects, but give the subjects a chance to get familiar with the product and context by, for example, riding a representative car under representative driving conditions before entering the laboratory. In this study, sound quality assessments of interior sounds of cars made by two groups were compared. In one group subjects were exposed to the same driving conditions that were later assessed in a laboratory listening test by taking them on a ride in one of the cars to be assessed, just before entering the laboratory. In the other group subjects made the laboratory assessments without prior car riding.
2015-06-15
Journal Article
2015-01-2263
Saeed J. Siavoshani, Prasad Vesikar
The intent of this paper is to document comprehensive test-based approach to analyze the door-closing event and associated sound using structural and acoustic loads developed during the event. This study looks into the door-closing phenomenon from the structural interaction point of view between the door and the body of the vehicle. The study primarily focuses on distributing the door and body interaction as discrete multiple structural and acoustic phenomena. It also emphasizes on the structural and acoustic loads developed by the discretized interactions at the interfaces between the door and the body frame. These interfaces were treated to be the load paths from the door to the body. The equivalent structural and acoustic loads were calculated indirectly using the well-known Transfer Path Analysis (TPA) methodology for structural loads and the Acoustic Source Quantification (ASQ) methodology for acoustic loads.
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