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Viewing 61 to 90 of 8994
2015-06-15
Technical Paper
2015-01-2205
John G. Cherng, Simeng Xing, Weiwei Wu, Jan Ladewig, Rolf Balte, Maurice Venegas
A comprehensive and systematic investigation on acoustical performance of carbon nanotube enhanced polyurethane (PU) foams was performed. The complete foam making process was carefully carried out in order to select a stable base foam composition that to be integrated with many carbon nanotube materials. A total of eight design parameters were evaluated, such as loading in weight percentage, diameter of the nanotube, length of the nanotube,coating with Ni, single and multiple layer nanotubes, graphitization of nanotube, radical bonding, and geometry configuration of nanotube, i.e. tube vs. sheet. Both normal incidence sound transmission loss (STL) and absorption coefficient were measured. It was found out that there is an optimum value in most of design parameters. In general, nanotube enhanced PU foam definitely demonstrated improvements in both absorption coefficients and sound transmission loss.
2015-06-15
Technical Paper
2015-01-2271
Yong Du Jun, Bong Hyun Park, Kang Seok Seo, Tae Hyun Kim, Myoung Jae Chae
An objective measure is proposed for seat riding comfort evaluation under low frequency (0~2 Hz) vibratory conditions which represents typical roll and pitch motions of driving motor vehicles. The related feeling due to this low frequency vehicle motion is termed ‘hold feeling’ because the seated body may tend to deviate from the defined seating position under such vehicle motion inputs. In the present study, dynamic pressure distribution measurements have been performed with a roll motion simulator at different frequencies between 0.3 and 1.0 Hz, to monitor the interface pressure change behavior of the seat-subject body. Temporal changes in body pressure in terms of the magnitude and the representative locations, and the time delay in pressure change at different regions of the seat are identified to be useful parameters for describing the subject's responses and with the subjective test results.
2015-06-15
Technical Paper
2015-01-2363
Albert Albers, Jan Fischer, Matthias Behrendt, Dirk Lieske
The driving comfort is an important factor for buying decisions. Especially for battery electric vehicles (BEV) the acoustic quality is an elementary distinguishing feature, since the masking of an internal combustion engine (ICE) is no longer present. For the interior noise of BEV high frequency tonal orders are characteristic. They can for example be caused by the gearbox or the electric drive and strongly influence the perception and rating of the interior noise by the customer. Opposing the importance of the acoustic quality is the lack of knowledge of how to measure, analyze and predict the high frequency tonal noise generated by the dynamic torque of the electric drive. In this contribution methods for measuring, analyzing and predicting the excitation by the dynamic torque of the electric drive are presented. The dynamic torque of the electric drive up to 3.5 kHz is measured on a component test bench with the help of high frequency and high precision digital torque transducer.
2015-06-15
Technical Paper
2015-01-2202
Catheryn Jackson, Justin E. Gimbal, Dhara Metla
Over the past decade damping materials have made major improvements in contributing to passenger comfort. NVH engineers have further shaped the material specifications to reflect key targeted properties that improve the 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
Technical Paper
2015-01-2219
Al Ganeshkumar, Shinichi Fukuhara
Active Noise Cancellation technology is widely used in automobiles to reduce engine harmonic noise. ANC systems require one or more microphones mounted in the cabin to monitor the harmonic noise level and provide feedback to the DSP algorithm. The ideal locations for the microphones are as close as possible to the passenger seating locations and away from any wind turbulence that can hit the diaphragm of the microphone. Excessive wind turbulence on the diaphragm can cause the ANC adaptive filter weights to be perturbed enough and cause audible ‘pumping’ type artifacts. For several practical reason it’s not always possible to control the location of the microphones and hence a DSP software and/or mechanical solution often needs to incorporated in the system. This paper will primarily address the DSP software solutions to detect wind turbulence noise in ANC microphones so appropriate counter-measures can be applied to eliminate the unwanted artifacts.
2015-06-15
Technical Paper
2015-01-2225
Peng Yu, Tong Zhang, Jing Li, Shiyang Chen, Rong Guo
Faced on transient vibration of EV, considering the characteristics of the electric drive system, active and passive integrated transient vibration control method of power train mounting system was proposed. First, models of power train system and mounting system were established, modal characteristics were grasped by simulation and experiment; a feed-forward controller was constructed from the active control perspective, mounting system transient vibration and power train torsion vibration were reduced; based on this, further optimization of mounting system was conducted from a passive control perspective. Results show that the active and passive integrated control method can effectively reduce the dynamic reaction force of mounting points, improve the vibration conditions of power train and body as well.
2015-06-15
Technical Paper
2015-01-2250
Masahiro Akei, Nobutaka Tsujiuchi, Akihito Ito, Takayuki Yamauchi, Daisuke Kubota
This paper describes the identification of the sound source model for the diesel engine installed on the agricultural machine by Inverse-Numerical Acoustic analysis (INA), and the noise prediction using the sound source model identified by INA. INA is a method to identify surface vibrations from surrounding sound pressures. This method is applicable for a complicated-shaped sound source like an engine. Although many studies about INA have been conducted, these past studies are the studies on improvement of the identified accuracy and noise prediction in the free sound field or hemi-free sound field. The authors predicted accurately sound pressure level of engine enclosure using sound source model identified by INA and boundary element method (BEM). However, we have not yet verified the effectiveness of sound source model against the enclosure which has an absorption material and an opening.
2015-06-15
Technical Paper
2015-01-2339
Márcio Calçada, Alan Parrett
Sound absorption materials can be key elements for mass-efficient vehicle noise control. They are utilized at multiple locations in the interior and one of the most important areas is the roof. At this location, the acoustic treatment typically comprises a headliner and an air gap up to body sheet metal. The performance requirement for such a vehicle subsystem is normally a sound absorption curve. Based on headliner geometry and construction, the sound absorption curve shape can be adjusted to increase absorption in certain frequency ranges. In this paper an overall absorption metric is developed to relate design parameters to an absorption curve shape which results in improved in-vehicle performance. This metric is based on sound absorption coefficient and articulation index. Johnson-Champoux-Allard equivalent fluid model and diffuse field equations are used. The results are validated using impedance tube measurements.
2015-06-15
Technical Paper
2015-01-2301
Maxwell Hill, Dan Luo, Mark Moeller
Wind noise can be a significant event for automotive design engineers. The greenhouse glass plays an important role in the wind noise process. Robust estimates of the greenhouse glass damping are necessary for both understanding and modeling the role of the glass in the wind noise process. One unanswered question is whether the aerodynamic loads affect the window glass damping. To make this determination a method to assess the operational damping is required. The civil engineering community uses the random decrement technique to assess operational damping due wind loads. The random decrement technique has been shown to be a normalized autocorrelation function. In this paper the damping is estimated directly from the autocorrelation function. In the first section the relationship between the damping and autocorrelation function is examined for white noise excitation. A single oscillator is examined as the first case. Extension to higher modal densities is discussed.
2015-06-15
Technical Paper
2015-01-2302
Yuksel Gur, Jian Pan, David Wagner
Light weighting 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 sound package materials and designs for use in lightweight vehicles. In this paper, we will focus on the use of SEA (Statistical Energy Analysis Tool) as a CAE design tool to develop sound packages for use in lightweight vehicle design to recover NVH deficiencies due to sheet metal light weighting actions. Statistical Energy Analysis results for vehicle level as well as dash and floor subsystem levels will be presented and SEA prediction capability for the sound package development for vehicle design will be discussed.
2015-06-15
Technical Paper
2015-01-2290
Sivanandi Rajadurai, Guru Prasad Mani, Kavin Raja, Sundaravadivelu Mohan
Bending moment is one of the strong pursuits in resonator's structural validation. Eigen problems play a key role in the stability and forced vibration analysis of structures. This paper explains the methodlogy to determine the weak points in the resonator assembly considering the additional effects of the installation forces and temperature impacts. Using strain eenergy plots, weakest part of the product is modified in the initial stage. The solution comes in a unique way of utilizing the worse case scenarios possible. As a consequence, the stress generated by these analyses will prove to be critical in concerning the durability issue of the system. These conditions are evaluated by a finite element model through linear and non- linear approaches and results summarized.
2015-06-15
Technical Paper
2015-01-2258
Gil-Jun Lee, Kichang Kim, Jay Kim
Squeak and rattle (S&R) noises are undesirable noises caused by friction-induced vibration or impact between surfaces. While several computer programs were developed to automatically detect and rate S&R events over the years, these programs could distinguish squeak and rattle noises from each other. Because the causes of squeak noises and rattle noises are different, distinguishing two types of noises will be very useful for automotive engineers in choosing an appropriate solution to reduce S&R noises. Authors developed a new algorithm to differentiate squeak noises and rattle noises utilizing a combination of sound quality metrics. Specifically, sharpness, roughness and fluctuation strength of the noises were employed in the algorithm. A three-dimensional space defined by the maximum values of sharpness, roughness, and fluctuation strength of the noise are used to differentiate two different types of noises. The developed algorithm was applied to 86 recorded squeak or rattle noises.
2015-06-15
Technical Paper
2015-01-2235
Arnaud Caillet, Denis Blanchet
The need in the automotive industry to understand the physical behavior of trims used in a vehicle is high. The PEM (poro-elastic method) was developed to permit an explicit representation of the trims in the FEM full vehicle models and to give tools to diagnose the effect of the trims and test design changes (porous material property, geometry…). During the last decade, the evolution on software and hardware sides have allowed to create models with a highly detailed trim description (Porous material using the Biot parameters, plastic trims...). These models can provide a good correlation up to 400Hz against the measurements compared to the classical NSM methodology which shows limitations.
2015-06-15
Technical Paper
2015-01-2240
Gong Cheng, David W. Herrin
The theory of patch (or panel) contribution analysis is first reviewed and then applied to a motorcycle engine on a test stand. The approach is used to predict the sound pressure in the far field and the contribution from different engine components to the sound pressure at a point. First, the engine is divided into a number of patches. The transfer function between the sound pressure in the field and the volume velocity of a patch is determined by taking advantage of vibro-acoustic reciprocity. An inexpensive monopole source is placed at the receiver point and the sound pressure is measured at the center of each patch. With the engine idling, a P-U probe was used to measure particle velocity and sound intensity simultaneously on each patch. The contribution from each patch to the target point is the multiplication of the transfer function and the volume velocity, which can be calculated from particle velocity or sound intensity. There were two target points considered.
2015-06-15
Technical Paper
2015-01-2211
Michael J. Santora, Dillon Savage
In the present study by the University of Idaho Clean Snowmobile Challenge (UICSC) team, the necessity, history, and research of noise reduction strategies in two-stroke snowmobile exhaust is presented. Testing and design is discussed to show the decision making process of College Design Series (CDS) teams. The UICSC CDS team is comprised of mechanical, electrical, and computer engineers. The development from static to dynamic noise cancellation is explained as a proof of concept and to further demonstrate CDS design. The study presents math models that validate each noise reduction technique. The noise reduction includes both a mechanically active quarter-wave resonator (MAQR) and mechanically active Helmholtz resonator (MAHR). Viability is given for both design types. These are presented with supporting implementation data. Control for both resonator platforms is discussed. The relative effect of each technology is compared based off cost and packaging.
2015-06-15
Journal Article
2015-01-2261
Joseph Plattenburg, Jason Dreyer, Rajendra Singh
Combined active and passive damping is an emerging trend as it should 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 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. Further scientific studies include a bench experiment that determines frequency dependent properties of the viscoelastic damping material. 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
2015-01-2270
Oliver Unruh, Christopher Blech, Hans Peter Monner
Global attenuation of structural velocities is one of the most effective approaches in order to reduce noise emitted by shell structures such as a car roof or aircraft fuselage panels. This global reduction can be achieved by the application of passive damping treatments like constraint layer damping on large fractions of the vibrating surface. The main disadvantage of this approach is the fact that it leads to increasing total cost and weight of the structure. To overcome this problem, acoustic black holes can be used to focus the energy of structure borne sound on some critical locations of the structure in order to dissipate it by a very limited application of damping treatments. Acoustic black holes are funnel shaped thickness reductions that attract sound radiating bending waves and allow a global vibration reduction by an acceptable use of additional damping.
2015-06-15
Technical Paper
2015-01-2266
Andrzej Pietrzyk
Several of the exterior noise sources existing around a vehicle can cause airborne noise issues at relatively low frequencies. One of them is exhaust pipe orifice noise. Traditional methods for handling airborne noise in vehicles, such as SEA, are not suitable for the frequency range of interest. Finite Element analysis has been used, but it often ends up with very heavy runs if semi-infinite acoustic elements are used at the outer boundary as the solution has to be direct instead of modal in this case. There are, however, some softwares that can handle this calculation relatively efficiently. One of the primary choices could be FFT&Actran. However, recently, a similar capability has been developed in MSC Nastran. Also, the calculations involving the free field impedance conditions have been made extremely efficient in CDH/AMLS. Including the poro-elastic material model for foam-based carpets is also becoming practically possible.
2015-06-15
Technical Paper
2015-01-2243
Yang Liu, Pingjian Ming, Wenping Zhang, Xinyu Zhang
Turbocharger is an important part of the turbocharged diesel engine. Due to the increase of mass flow rate and pressure ratio the turbocharger, aerodynamic noise of turbocharger has become more apparent. And turbocharger noise becomes one of the major noise sources of the main engine system of the ship. In the paper, Based on Lighthill acoustic analogy theory, by using Computational fluid mechanics(CFD) and indirect boundary element method(IBEM), the aerodynamic noise prediction of marine turbocharger compressor is developed. On the basis of finite volume method, using the single stator and rotor blade passages, unsteady viscous flow in the centrifugal Compressor was simulated. The compressor’s flow characteristic was predicted and agree well with the experimental value. The flow field characteristics and frequency spectrum of the fluctuating pressure which agree well with the theoretical value were analysed.
2015-06-15
Journal Article
2015-01-2275
Manfred Koberstein, Zhengyu Liu, Curtis Jones, Suhas Venkatappa
In the thermal expansion valve (TXV) refrigerant system, transient high-pitched whistle at 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
Technical Paper
2015-01-2244
Ulhas Mohite, Niket Bhatia, Prashant Bhavsar
Noise radiated from motorcycle engine is gaining significance not only to meet regulations but also to fulfil customer demands of quiet products. In IC engines, combustion pressure is one of the major excitations which is transmitted through powertrain to the casings and radiate noise. Early identification and correction of the casing critical areas contributing to noise will lead to substantial cost and development time reduction. In this paper the approach to predict engine noise under combustion forces is presented. This Methodology is divided into three stages: 1. Multi body dynamic (MBD) Simulation to determine excitation forces 2. Vibration analysis of engine under combustion load 3. Acoustic analysis of engine to predict Sound Pressure Level (SPL). Important parts of motorcycle engine with single cylinder are considered as flexible bodies for MBD simulation.
2015-06-15
Technical Paper
2015-01-2247
Masao Nagamatsu
The sound localization methods are used for noise source detection of prototype of mechanical products including automobile engines. There are several types of sound localization methods. In middle frequency sound localization around 1kHz, which is most sensitive band for human auditory, these methods have enough resolution in reconstructed images, and are effective to localize the sound source. In high frequency sound localization, the holographic type methods take long time in measurement. To overcome this problem, I have developed the converted method of Nearfield Acoustic Holography (NAH) method, which is one of conventional holographic sound localization method. However, in low frequency sound localization, all methods do not have enough resolution in reconstructed images. I am now developing new sound localization method, Double Nearfield Acoustic Holography (DNAH) method. This method is converted method of conventional Nearfield Acoustic Holography method.
2015-06-15
Technical Paper
2015-01-2251
Alex Varghese, Satish Palled
Background: NVH in Automobile has been very demanding over the years and is considered to be one of the Key focus areas for Customer Satisfaction identified by the Automobile companies. Also the end customer or Automobile users are becoming more conscious about the NVH performance. In today’s world the NVH Department of Automobile companies are mainly focusing on the three Governing factors, a) Performance b) Weight and c) Cost. Also lot of work is been done on finding new ways of testing and evaluating noise levels and predicting the noise path for effective noise treatments. The need of Noise treatment materials along the Noise path becomes very crucial for Noise treatment. Lot of work has been done towards optimizing noise treatment materials and its effective placement to suit performance, weight and cost. The treatment of these noise sources becomes an Engineering art as it involves these combinations of noise sources.
2015-06-15
Journal Article
2015-01-2328
Barbara Neuhierl, Sivapalan Senthooran, Reinier Toppinga, Anke Jäger, Maarten Brink, Timo Lemke, Philippe Moron, Raghu Mutnuri
The object of the validation study presented in this paper is a generic vehicle, the so-called SAE body, developed by a consortium of german car manufacturers (Audi, Daimler, Porsche, Volkswagen). It consists of a simplified cabin whose interior can be equipped with either reverberant or partly absorbing walls. To obtain more realistic flow and pressure excitation typical for production vehicles, an a-pillar and a series rear view mirror were attached to the exterior surface. Furthermore the test object contains a glass side window, allowing noise transmission to the interior. Many experiments have been performed by the abovementioned consortium on this object in the past to investigate its behavior when exposed to fluid flow. Some of these experiments were used to validate the simulation results discussed in the present paper.
2015-06-15
Technical Paper
2015-01-2319
Uije Kim, Matthew Maunder, Phil Grant, Duncan Mawdsley
A new pass-by noise test method has been introduced, in which engine speeds and loads are reduced (compared to the old test method) to better reflect real world driving behaviour. New noise limits come into effect on 1 July 2016, and tighten by up to 4dB by 2026. The new test method is recognised internationally, and it is anticipated that the limits will also be adopted in most territories around the world. To achieve these tough new pass-by noise requirements, vehicle manufacturers need to address several important aspects of their products. Vehicle performance is critical to the test method, and is controlled by engine torque, speed of response to accelerator pedal input, transmission type, overall gear ratios, tyre rolling radius, and resistance due to friction and aerodynamic drag. Noise sources (exhaust, intake, powertrain, driveline, tyres) and vehicle noise insulation are critical to the noise level radiated to the far-field.
2015-06-15
Journal Article
2015-01-2333
Brandon Sobecki, Patricia Davies, J Stuart Bolton, Frank Eberhardt
Component sound quality is an important factor in the design of competitive diesel engines. One component noise source that causes complaints is the gear rattle that originates in the front-of-engine gear train which drives the fuel pump and other accessories. The rattle is caused by repeated tooth impacts resulting from fluctuations in differential torsional acceleration of the driving gears. These impacts generate a broadband, impulsive noise that is often perceived as annoying. In most previous work, the overall sound quality of diesel engines has been considered without specifically focusing on predicting the perception of gear rattle. Gear rattle level has been quantified based on angular acceleration measurements, but those measurements can be difficult to perform. Here, the emphasis was on developing a metric based on subjective testing of the perception of gear rattle.
2015-06-15
Journal Article
2015-01-2276
Zhengyu Liu, Donald Wozniak, Manfred Koberstein, Curtis Jones, Jan Xu, Suhas Venkatappa
Refrigerant flow-induced gurgling noise is perceived in automotive refrigerant systems which equipped with variable displacement compressors. In this study, the condition of the gurgling generation is investigated in vehicle level and the fundamental root cause is identified as the two-phase refrigerant flow entering the TXV. By conducting literature review, the acoustic characteristics of the flow patterns and the parameters affecting the flow regimes in horizontal and vertical tubes are summarized, and then the gurgling mechanism is explained as that 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 sub-system (RSS) level. Finally, the guidelines for the attenuation and suppression of the gurgle are provided.
2015-06-15
Technical Paper
2015-01-2208
David Stotera, Scott Bombard
Both vehicle roof systems and vehicle door systems typically have viscoelastic material between the beams and the outer panel. These materials have the propensity to affect the vibration decay time and the vibration level of the panel with their damping and stiffening properties. Decay time relates to how pleasant a vehicle door sounds upon closing, and vibration level relates to how loud a roof boom noise may be perceived to be by vehicle occupants. If a surrogate panel could be used to evaluate decay time and vibration level, then a design of experiments could be used to compare the effects of different factors on the system. The factors were varied in laboratory tests, and the results were calculated using design of experiments software. In this paper the results of a study of the varying factors tested with respect to their effects on decay time and vibration level are presented, as well as the effect the results had on potential optimization of the systems.
2015-06-15
Technical Paper
2015-01-2201
Paul B. Murray, Jason T. Kunio, Leif Christensen, Flemming S. Larsen
Acoustic material testing is becoming increasingly relevant to engineers, designers and manufacturers from a broad range of industries. This paper presents comparisons between material absorption measurements made using the traditional approaches of the reverberation room method and the fixed impedance tube using a sample holder, and compares the results with those obtained using a new portable flanged impedance tube method. The portable tube allows fast non-destructive in-situ material measurements. They therefore include the impact of the installed lay-up (e.g. effects of facing sheets, curvature, material compression, bagging, etc). Comparison between the varying measurement techniques shows that the portable meter data are more repeatable than both the reverberation room and sample holder procedures. The repeatability of the reverberation room absorption results is subject to variations in panel edge diffraction, non-diffuse field conditions, and source/ receiver repeatability.
2015-06-15
Journal Article
2015-01-2265
Murali Balasubramanian, Ahmed Shaik
Automotive manufacturers are being challenged to come up with radical solutions to achieve substantial (30-35%) vehicle weight reductions without compromising Safety, Durability, Handling, Aero-thermal or Noise, Vibration and Harshness (NVH) performance. Developing light weight vehicle enablers have assumed foremost priority amongst vehicle engineering teams in order to address the stringent Fuel Economy Performance (FEP) targets while facilitating lower CO2 emissions, downsizing of engines, lower battery capacities etc. Body sheet metal panels have become prime targets for weight reductions via gage reduction, high strength steel replacement, lighter material applications, lightening holes etc. Many of these panel weight reduction solutions are in sharp conflict with NVH performance requirements.
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