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2015-09-15
Technical Paper
2015-01-2477
Alessandro Gardi, Roberto Sabatini
A number of initiatives are aiming at assessing and reducing the impact of air transport on the environment. This extensive endeavour is soliciting a substantial evolution in the measurement of the environmental impacts and on the assessment of the effective gains attained by the R&D outcomes. Legislation is already being progressively extended in several countries to limit or penalise noise emissions, and analogous regulatory actions can be foreseen with respect to atmospheric pollutants. This research activity is developing laser-based Light Detection and Ranging (LIDAR) systems for characterisation of gaseous pollutants and particulate concentrations in high space and time resolutions. The employed measurement principle is based on Differential Absorption LIDAR technique, in a bistatic layout. After the initial feasibility study, two candidate bistatic system layouts have been proposed.
2015-09-15
Technical Paper
2015-01-2605
Jamnie Yazmín Achem Calahorra, Hilda E. Esparza Ponce, Patricia Zambrano Robledo, Facundo Almeraya Calderón, Citlalli Gaona Tiburcio
Thin films deposited by magnetron sputtering are review in terms of their potential and present uses in the aircraft industry. The aircraft alloys substrates were Ti-6Al-4V and Incoloy 800H/HT, using a target of YSZ with nominal composition of 8% Y2O3 (wt%) and the remainder of ZrO2. The chemical composition of the films was determined by EDX. The electrochemical noise behavior show that the coatings decreased propagation of pitting, leading to a state of passivation or uniform corrosion, and also possess superior corrosion resistance over the individually substrates.
2015-09-15
Technical Paper
2015-01-2435
Ramakrishnan Murthy
One major problem that any product (say Motor, engines etc) which converts electrical energy into a mechanical energy would have is resonance. It has tendency to damage any material when the products operating frequency matches the resonant frequency. The major consequences of this resonant frequency in Flight at run-time could be catostrophic. Generally it is a practice to avoid running at the resonant frequency. This is done as a fixed method where the systems are designed not to run on resonant frequency, i.e. a subsystem in a system is now being designed for that system alone which will not match the resonant frequency. But the same subsystem may not be suitable for some other system. Hence this requires multiple designs. However this idea is to make a design generic where any subsystem can be used in any system irrespective of its resonant frequency. The technique uses the PID algorithm. This method will be helpful is having a single design for different systems.
2015-09-06
Journal Article
2015-24-2527
Daniela Siano, Giovanni Ferrara, Giulio Lenzi, Danilo D'Agostino, Andrea Fioravanti
In an Internal Combustion Engine, the design of the intake system is a very critical aspect since it affects both the engine power output and noise emissions at the intake side. In particular, downsized VVA engines typically produce higher gas-dynamic noise levels since, due to the intake line de-throttling at part-load, a less effective attenuation of the pressure waves is realized. In this work, the acoustic performance of the intake air filter of a commercial VVA engine is numerically and experimentally analyzed. In particular, a FEM model of the system is realized in order to compute the Transmission Loss (TL) parameter of the base device. The numerical analysis is performed considering the absence or the presence of a mean flow inside the device, and accounts of fluid-structure interaction, which gives the possibility to determine the effect of structure participation on the TL profile.
2015-09-06
Technical Paper
2015-24-2526
Borislav Klarin, Thomas Resch, Chiara Sessarego, Giorgio Spanu, Gianni Lamonaca
Modern engines with low number of cylinders (I4, I3, I2) are typically equipped with a mass balancing unit to reduce free mass forces and moments and to keep powerunit vibrations, transferred via the mounts into the chassis, on an acceptable level and by that meet the required comfort quality. Typical disadvantages of mass balancing systems are increased friction, which reduces the engine efficiency, but also space, costs, increased complexity and negative effect on the engine acoustics. Especially the latter is defined by the design of the drive for the balancer unit. In many cases, this is realized by a gear drive, directly driven from the crankshaft. Therefore, special care has to be taken for the layout of this gear(s) to avoid potential rattle, gear tooth failure and negative noise transfer from gear contact to the housing structure (e.g. increased axial excitation due to selection of helix angle).
2015-09-06
Journal Article
2015-24-2462
Fabio Auriemma, Heiki Tiikoja
The acoustic impedance exerted by a new type of element for noise control, the Micro-Grooved Elements (MGEs), has been broadly studied in this paper. The MGEs are typically composed of at least two overlying layers presenting macroscopic slots and a number of micro-grooves at least on one of the contact surfaces. Similarly to the Micro-Perforated Elements (MPEs), the MGEs have been proved to provide effective dissipation of acoustic energy by the means of viscous losses taking place in the micro-channels. However, in contrast to the typical MPEs, the MGEs use the grooves, instead of the holes, which the air is forced to pass through. It results in more cost effective elements, which have been found to represent an adequate alternative for fibrous materials, typically present in silencer units. This study represents a refined investigation on the acoustic impedance of the MGEs, aiming to provide a general formulation, valid for different internal configurations.
2015-06-29
WIP Standard
J1400
This SAE Recommended Practice presents a test procedure for determining the airborne sound barrier performance of materials and composite assemblies commonly installed in surface vehicles and marine products. This document is intended to provide a means of rank ordering barrier materials according to their sound transmission loss. At each test frequency the transmission loss (TL) is projected from the measured noise reduction of the test specimen using a correlation factor (CF). The respective CF for the test condition is determined as the differences between the measured noise reduction (MNR) of a homogeneous limp panel, such as lead, and its calculated field-incidence transmission loss. Latitude is permitted in certain test conditions that do not necessarily conform to all of the acoustical requirements of ASTM E 90.
2015-06-23
WIP Standard
J2889/1
This SAE Standard is derived from SAE J2805 and specifies an engineering method for measuring the sound emitted by M and N category road vehicles at standstill and low speed operating conditions.. The specifications reproduce the level of sound which is generated by the principal vehicle sound sources consistent with stationary and low speed vehicle operating conditions relevant for pedestrian safety. The method is designed to meet the requirements of simplicity as far as they are consistent with reproducibility of results under the operating conditions of the vehicle. The test method requires an acoustic environment which is only obtained in an extensive open space or in special designed indoor facilities replicating the conditions of an extensive open space. Such conditions usually exist during: Measurements of vehicles for regulatory certification. Measurements at the manufacturing stage. Measurements at official testing stations.
2015-06-15
Technical Paper
2015-01-2329
Paolo Di Francescantonio, Charles Hirsch, Piergiorgio Ferrante, Katsutomo Isono
Abstract A new method called Adaptive Spectral Reconstruction (ASR) for the stochastic reconstruction of broadband aeroacoustic sources starting from steady CFD analyses is presented and applied to the evaluation of the noise radiated by a model automotive side mirror. The new approach exploits some ideas from both SNGR and RPM, and for some aspects can be considered as a sort of mixing between the two methods since it permits to reconstruct both the frequency content of the turbulent field (as done by SNGR) and the spatial cross correlation (as done by RPM). The turbulent field is reconstructed with a sum of convected plane waves, but two substantial differences are introduced in respect of SNGR. The first difference concerns the spatial variation of the parameters that define each wave, that depends on the wavelength of each wave, rather than being kept constant or related to the CFD correlation length.
2015-06-15
Technical Paper
2015-01-2326
Denis Blanchet, Anton Golota
Abstract Recent developments in the prediction of the contribution of wind noise to the interior SPL have opened a realm of new possibilities. The main physical mechanisms related to noise generation within a turbulent flow and the vibro-acoustic transmission through the vehicle greenhouse is nowadays better understood. Several simulation methods such as CFD, FEM, BEM, FE/SEA Coupled and SEA can be coupled together to represent the physical phenomena involved. The main objective being to properly represent the convective and acoustic component within the turbulent flow to ensure proper computation of the wind noise contribution to the interior SPL of a vehicle.
2015-06-15
Technical Paper
2015-01-2308
Yitian Zhang, David W. Herrin
Abstract The two-load method is commonly applied to determine the transmission loss for a muffler especially if an impedance tube rig is used. Although one procedure and algorithm is detailed in ASTM E2611, the quality of the transmission loss curve is dependent on several factors that are not discussed in detail in the standard. In this paper, several practical concerns are investigated including (1) the number of channels used in the measurement, (2) the selection of the reference channel, and (3) the choice of data processing algorithm (transfer or scattering matrix). Results are compared for a simple expansion chamber first, then for mufflers of other types. Recommendations are made for obtaining smoother transmission loss curves for various measurement methods.
2015-06-15
Technical Paper
2015-01-2309
David Neihguk, M.L. Munjal, Abhinav Prasad
Abstract The bias flow in Concentric Tube Resonator (CTR) is a flow-induced phenomenon in which the pressure gradient along the radial direction is produced by the kinetic energy of the flow. As a result, the flow dynamics in CTR is characterized by bias flow into the annular cavity in the upstream and outflow from the annular cavity in the downstream of the flow. This is due to the change in direction of the radial component of the bias flow at a point called the point of recovery, as a consequence of mass conservation. The pressure drop of CTR is a complex function of the momentum flux and other geometric parameters such as porosity, open area ratio, discharge coefficient of the perforated holes, bias inflow, bias outflow, grazing flow and length. In this study, numerical experiments are conducted to obtain an empirical formula for the friction factor of perforated pipes which are extensively used in automotive mufflers.
2015-06-15
Technical Paper
2015-01-2303
Katherine Tao, Alan Parrett, David Nielubowicz
Abstract The headliner system in a vehicle is an important element in vehicle noise control. In order to predict the performance of the headliner, it is necessary to develop an understanding of the substrate performance, the effect of air gaps, and the contribution from any acoustic pads in the system. Current Statistical Energy Analysis (SEA) models for predicting absorption performance of acoustic absorbers are based on material Biot properties. However, the resources for material Biot property testing are limited and cost is high. In this paper, modeling parameters for the headliner substrate are identified from a set of standard absorption measurements on substrates, using curve fitting and optimization techniques. The parameters are then used together with thickness/design information in a SEA model to predict the vehicle headliner system absorption performance.
2015-06-15
Technical Paper
2015-01-2301
Maxwell Hill, Dan Luo, Mark Moeller
Abstract 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 to 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
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
2015-01-2313
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
2015-01-2310
Edward Ray Green
Abstract The Sound Transmission Loss of automotive intake and exhaust components is commonly measured using the four microphone tube method per ASTM E2611 [1]. Often area adapters are used to match the component diameter to that of the tube apparatus. These area adapters affect the Sound Transmission Loss measurement, especially at very low frequencies. The use of the Transfer Matrix Technique to remove the effect of the area adapters is described. The improvements for step and cone area adapters are compared.
2015-06-15
Technical Paper
2015-01-2358
Rod Morris-Kirby, Evan Harry, Dirk Jaeger, Bernd Borgmann
Abstract Acoustic Diagnostic Network Algorithms (DNA) are experimental methods that extract airborne acoustic characteristics from a motor vehicle and decompose this information into a set of networks from which the source, path and receiver noise sources and paths can be determined. Unlike traditional transfer path analysis Acoustic DNA takes the problem into the fine detail. It answers questions such as what, where and how does a vehicle's acoustic systems need to be changed in order to achieve any given objective. This paper describes the fundamental methodology and features together with how it has been implemented into a computer program that has been used successfully in over 50 vehicle projects within the Authors Research and Development group on a wide range of motor vehicles.
2015-06-15
Technical Paper
2015-01-2351
Hongyu Shu, Shuang Luo, Li Wang
Abstract In order to measure the noise of auto shock absorbers, a test bench used to detect piston-rod vibration responses of shock absorbers and measuring analyzer named SANTS-I were developed. The vibration response data was detected by bench tests, which shows that there are high-frequency violent peaks on the sine curve of piston-rod oscillating with relative low frequency. In order to explain the interior work dynamic mechanism of shock absorbers, a schematic Micro-process Dynamic Model with 10 steps particularly divided extension and compression stroke in more detail, and dynamic differential equations for each step were presented and discussed. Furthermore, numerical simulation for the inner impacts interaction between piston and damping fluid of hydraulic shock absorber was realized by ADINA software, by the establishment of a gas-liquid two-phase finite element model.
2015-06-15
Journal Article
2015-01-2363
Albert Albers, Jan Fischer, Matthias Behrendt, Dirk Lieske
Abstract The driving comfort is an important factor for buying decisions. For the interior noise of battery electric vehicles (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. 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, high precision torque transducer. The analysis of the results for the order of interest shows a good correlation with the acoustic measurements inside the corresponding vehicle. In addition an experimental and numerical modal analysis of the rotor of the electric drive are performed.
2015-06-15
Technical Paper
2015-01-2367
David Lennström, Arne Nykänen
Abstract When it comes to the acoustic properties of electric cars, the powertrain noise differs dramatically compared to traditional vehicles with internal combustion engines. The low frequency firing orders, mechanical and combustion noise are exchanged with a more high frequency whining signature due to electromagnetic forces and gear meshing, lower in level but subject to annoyance. Previous studies have highlighted these differences and also investigated relevant perception criteria in terms of psycho-acoustic metrics. However, investigations of differences between different kinds of electric and hybrid electric cars are still rare. The purpose of this paper was to present the distribution of tonal components in today's hybrid/electric vehicles. More specifically, the number of prominent orders, their maximum levels and frequency separation were analyzed for the most critical driving conditions. The study is based upon measurements made on 13 electrified cars on the market.
2015-06-15
Technical Paper
2015-01-2365
Zhaohui Sun, Glen Steyer, Jason Ley
Abstract Alternative powertrains, in particular electric and plug-in hybrids, create a wide range of unique and challenging NVH (noise, vibration & harshness) issues in today's automotive industry. Among the emerging engineering challenges from these powertrains, their acoustic performances become more complicated, partially due to reduced ambient masking noise level and light weight structure. In addition, the move away from conventional displacement engines to electrical drive units (EDU) has created a new array of NVH concerns and dynamics, which are relatively unknown as compared to the aforementioned traditional setups. In this paper, an NVH optimization study will be presented, focusing on four distinct factors in electric drive unit gear mesh source generation and radiation: EDU housing and bearing dynamics, gear geometry, EDU shafting torsional dynamics, and EDU housing structure. The study involves intensive FEA modeling/analyses jointly with physical validation tests.
2015-06-15
Technical Paper
2015-01-2359
Craig Reynolds, Jason Blough, Carl Anderson, Mark Johnson, Jean Schweitzer
Sound power can be determined using a variety of methods, but precision methods require the volume of the noise source to be less than 1% of the chamber volume leading to relatively large test chambers. Automotive torque converter performance and noise testing is completed in an enclosed metallic test fixture which inhibits the use of precision methods due to volume and space limitations. This paper describes a new method developed to accurately determine sound power of an automotive torque converter in a relatively small enclosure through characterization of the test environment. The test environment was characterized using two reference noise sources designed to represent torque converter noise output and physical geometry. Sound pressure levels of the sources were measured at multiple microphone locations and at three source amplitude levels to characterize the environment.
2015-06-15
Technical Paper
2015-01-2361
Sajjad Beigmoradi
Abstract Nowadays, by the introduction of significant advances in automotive industries, noise, vibration and harshness (NVH), in the position of the main comfort attribute, plays a crucial role in marketing and passenger satisfaction. In order to cope NVH problems, three main actions are taken by NVH engineers for reducing perceived level of noise in cabin: Noise reduction in sources, Noise path treatment and Noise control at receiver. Among these approaches, those pertain to modification of noise pass, through structure and air, to the cabin are more prevalent in automotive applications. Accordingly, identification of noise paths that dominantly contribute to sound and vibration transfer to cabin phenomenon should be dealt with importance. In practice, engine vibration transmitted through sub-frame attachments to body can induce high level of noise and vibration to the passenger cabin.
2015-06-15
Technical Paper
2015-01-2338
Dong Guo, Quan Shi, Peng Yi
Abstract In-vehicle noise is composed of a variety of tonal (frequency-related) components and the tonal components play an important role in the improvement of interior vehicle sound quality. Much research has been focused on the suppression of sound pressure level and achieved certain positive effects. However, in some operating conditions, customers still perceive the tonal components and complain about the vehicle quality even the sound pressure level is relatively low. Therefore, a better understanding of how tonal components are perceived is necessary for automotive designers. To do so, psychoacoustics results about human hearing mechanism to tonal components are comprehensively summed in this study: human hearing response to pure tone, two tones and multiple tones. Then, well-controlled testing stimuli were generated and subjective annoyance testing was conducted. The results show agreement with former researchers' findings.
2015-06-15
Technical Paper
2015-01-2339
Márcio Calçada, Alan Parrett
Abstract 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 the body sheet metal. The acoustic 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 acoustic 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
2015-01-2348
Richard Kolano
Abstract This paper presents the results of a study to reduce the background noise level within a large Quiet Room located adjacent to other laboratory testing environments and below a mechanical mezzanine which houses an extensive array of mechanical and electrical equipment including banks of low-temperature chiller compressors, air handling units, and electrical switchgear that serves the entire building complex. This equipment was installed atop the concrete mezzanine floor deck without provisions for isolating vibration. As a result, structure-borne noise from that equipment travels through the floor, radiates from the underside of the floor deck, and intrudes into the Quiet Room below. This causes the background noise level within the Quiet Room to be too high for conducting low sound level measurements and studies on vehicles brought into the Quiet Room.
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
Technical Paper
2015-01-2345
Arnaud Duval, Valérie Marcel, Ludovic Dejaeger, Francis Lhuillier, Moussa Khalfallah
Abstract The Flaxpreg is a green and light very long flax fibers thermoset reinforced sandwich, which can be effectively used as multi-position trunk loadfloor or structural floor in the passenger compartment of a vehicle. The prepreg FlaxTapes of about 120 g/m2 constituting the skins of the sandwich, are unidirectionally aligned flax fibers tapes, with acrylic resin here, easily manipulable without requiring any spinning or weaving step and thus without any negative out of plane crimping of the almost continuous flax fibers. Thanks to their very low 1.45 kg/dm3 density combined with an adaptive 0°/90°/0° orientation of the FlaxTapes (for each skin) depending on the loading boundary conditions, the resulting excellent mechanical properties allow a - 35% weight reduction compared to petro-sourced Glass mat/PUR sandwich solutions (like the Baypreg).
2015-06-15
Technical Paper
2015-01-2176
Rajkumar Bhagate, Ajinkya Badkas, Kiran Mohan
Abstract Gear rattle is an annoying noise phenomena of the automotive transmission, which is mainly induced by torsional fluctuation of engine. In this study, torsional vibration of 3 cylinder powertrain is analyzed and improved for reducing the gear rattle from transmission by using parametric optimization. One dimensional Multi-body mathematical model for the torsional vibrations of front wheel drive automotive drivetrain is developed and utilized for the optimization of sensitive parameters of the driveline. Second order differential equations of the mathematical model are solved by using MATLAB and the output response is validated with the test data. Parametric optimization is conducted by using design of experiment method. The updated model is further utilized for optimizing the flywheel inertia, driveshaft stiffness and clutch stiffness. Mathematical modelling and optimization process has helped to achieve NVH targets for driveline.
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