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Viewing 1 to 30 of 7768
2017-06-17
Journal Article
2017-01-9550
David Neihguk, M. L. Munjal, Arvind Ram, Abhinav Prasad
Abstract A production muffler of a 2.2 liter compression ignition engine is analyzed using plane wave (Transfer Matrix) method. The objective is to show the usefulness of plane wave models to analyze the acoustic performance (Transmission Loss, TL) of a compact hybrid muffler (made up of reactive and dissipative elements). The muffler consists of three chambers, two of which are acoustically short in the axial direction. The chambers are separated by an impervious baffle on the upstream side and a perforated plate on the downstream side. The first chamber is a Concentric Tube Resonator (CTR). The second chamber consists of an extended inlet and a flow reversal 180-degree curved outlet duct. The acoustic cavity in the third chamber is coupled with the second chamber through the acoustic impedances of the end plate and the perforated plate.
2017-06-05
Technical Paper
2017-01-1842
Akin Oktav, Cetin Yilmaz, Gunay Anlas
As a countermeasure to trunk lid slam noise, reactive openings are used in the trunk cavities of passenger vehicles. In sedans trunk and cabin cavities are coupled acoustically through discontinuities on the parcel shelf and/or the rear seat. In such a case, these openings behave as if necks of a Helmholtz resonator, which in turn change the acoustic response of the system, accordingly. The Helmholtz resonator effect of the trunk cavity is discussed analytically through a simplified cavity model. A case study is also given, where the acoustic response of a sedan is analyzed through the computational model that considers the resonator effect. Sound pressure level results show that instant pressure drops and damping effects observed in the acoustic response can be explained with the resonator effect. Results obtained from the computational model of the sedan are verified by road test measurements
2017-06-05
Technical Paper
2017-01-1883
Arnaud Duval, Guillaume Crignon, Mickael Goret, Maxime Roux
The lightweighting research on noise treatments since years tends to prove the efficiency of the combination of good insulation with steep insulation slopes with broadband absorption, even in the context of bad passthroughs management implying strong leakages. The real issue lies more in the industrial capacity to adapt the barrier mass per unit area to the acoustic target from low to high segment or from low petrol to high diesel sources, while remaining manipulable. The hybrid stiff insulator family can realize this easily with hard felts barriers backfoamed weighting from 800 g/m² to 2000 g/m² typically with compressions below 10 mm. Above these equivalent barrier weights and traditional compressions of 7 mm for example, the high density of the felts begins to destroy the porosity and thus the absorption properties (insulation works anyway here, whenever vibration modes do not appear due to too high stiffness…).
2017-06-05
Technical Paper
2017-01-1830
Thomas Haase, Henning Bühmann, Martin Radestock, Hans Peter Monner
Due to the strengthened CO2 and NOX regulations future vehicles has to be lightweight and efficient. But, lightweight structures are prone to vibrations and radiate sound efficiently. Therefore, an active approach for reducing sound radiation from structures is the active structural acoustic control (ASAC). Since the early 90’s, several theoretical studies regarding ASAC systems were presented, but only very little experimental investigations can be found for this alternative to passive damping solutions. The theoretical simulations show promising results of ASAC systems compared to active vibration control approaches. So, for that reason in this paper an experiment is conducted to investigate the performance of an ASAC system in the frequency range up to 600 Hz. A regular sensor grid of 24 accelerometers that are interconnected to establish six radiation signals is applied to an aluminum plate.
2017-06-05
Technical Paper
2017-01-1848
Richard DeJong
From 1983 to 1995, Richard H. Lyon published several papers on Statistical Phase Analysis, showing that the average phase of the transfer functions in complex systems grows with frequency in proportion to the modal density of the system. In one dimensional systems this phase growth is the same as that of freely propagating waves. However, in two and three dimensional systems this phase growth is much larger than the corresponding freely propagating wave. Recent work has shown that these phase growth functions can be used as mode shape functions in discrete system models to obtain results consistent with Statistical Energy Analysis. This paper reviews these results and proposes naming the statistical mode shape functions in honor of Lyon.
2017-06-05
Technical Paper
2017-01-1775
Mark A. Gehringer, Robert Considine, David Schankin
This paper describes recently developed test methods and instrumentation to address the specific noise and vibration measurement challenges posed by large diameter single-piece tubular aluminum propeller shafts with high modal density. The application described in this paper is a light duty truck, although the methods described are applicable to any rotating shaft with similar dynamic properties. To provide a practical example of the newly developed methods and instrumentation, rotating and non-rotating data were acquired in-situ for several propeller shafts of varying construction, including both lined and unlined shafts. Data were also acquired with and without a torsional tuned vibration absorber attached to the driveline. The example data exhibit features that are uniquely characteristic of large diameter single-piece tubular shafts with high modal density, including the particular effect of shaft rotation on the measurements.
2017-06-05
Technical Paper
2017-01-1773
Jing Yuan
The dual phase twin synchronous drive has been developed for belt noise reduction. Two identical synchronous belts are arranged parallel side by side with one tooth staggered against other by the half pitch. The noise cancellation effect is achieved as one belt tooth engagement coincides with the other belt tooth dis-engagement. A center flange is used as a divider to prevent the belts contacting each other along the axial direction during their entrance and exit of the sprocket. An overall 20 [dBA] noise reduction has been achieved with the dual phase twin belt system compared to an equal width single belt counterpart. The vibration amplitude of the hub load is also reduced which is directly correlated to the structural borne noise. Comparing to the related dual phase helical tooth belt, also known as the eagle belt trade marked by Goodyear, the dual phase twin belt is superior in torque carrying capability; and is on par with noise mitigation.
2017-06-05
Technical Paper
2017-01-1784
Guillaume Baudet
Automotive wind noise’s physic is complex : noise for passengers depend of : - acoustic transfer function in the cabin - transfer loss of seals and panels - first of all, exterior loading due to the flow around the vehicle For some years, we know that the exterior loading can and must be split in two parts : - Hydrodynamic (or turbulent) loading with high wave number pressure field - Acoustic loading with low wave number pressure field In simulation people start to separate the two pressure fields by complex signal processing. But in real life test, there is no simple method to do so. In this paper we present an inverse method, call “Panel Inverse Method” (PIM) which can extract the low wave number loading measured on a vehicle panel. The method may be known with the French “RIFF” name. It is based on acceleration measurement of the panel to calculate the pressure which create panel’s motion : that’s typically an inverse method.
2017-06-05
Technical Paper
2017-01-1785
Paul Bremner, Scott Clifton, Chris Todter
Measurements of interior wind noise sound pressure level have shown that dBA and Loudness are not adequate metrics of wind noise sound quality due to non-stationary characteristics such as temporal modulation and impulse. A surface microphone array with high spatio-temporal resolution has been used to observe the corresponding non-stationary characteristics of the exterior aero-acoustic loading. Wavenumber filtering is used to observe the unsteady character of the low wavenumber aero-acoustic loading components capable of exciting glass vibration and transmitting sound.
2017-06-05
Technical Paper
2017-01-1783
Chris Todter, Olivier Robin, Paul Bremner, Christophe Marchetto, Alain Berry
Fluctuating surface pressure measurements using microphone arrays are still challenging, especially in an automotive context with cruising speeds around Mach 0.1. The separated turbulent boundary layer excitation and the side mirror wake flow generate both acoustic and aerodynamic components, which have wavenumbers that differ by a factor of approximately 10. This calls for high spatial resolution measurements to fully resolve the wavenumber-frequency spectrum. In SAE paper 2015-01-2325, the authors reported a micro-electro-mechanical (MEMS) surface microphone array that successfully used wavenumber analysis to quantify acoustic versus turbulence loading. It was shown that the measured surface pressure at each microphone could be strongly influenced by self noise induced by the microphone ”packaging”, which can be attenuated with a suitable windscreen.
2017-06-05
Technical Paper
2017-01-1769
Onkar Gangvekar, Santosh Deshmane
In today's automobile market, most of OEM's uses manual transmission for Cars. Gear Shifting is a crucial customer touch point. Any issue or inconvenience caused while shifting gear can result into customer dissatisfaction and will affect the brand image. Synchronizer is a vital subsystem for precise gear shifting mechanism. Based on vehicle application selection of synchronizer for given inertia and speed difference is the key factor which decides overall shift quality of gearbox. For more demanding driver abuse conditions like skip shifting, conventional brass synchronizers have proved inadequate for required speed difference and gear inertia and which eventually results into synchronizer crashing and affects driving performance. To increase synchronizer performance of multi-cone compact brass synchronizer, a grit blasting process has been added. These components are tested with Accelerated test plan successfully.
2017-06-05
Technical Paper
2017-01-1820
Martin Sopouch, Josip Hozmec, Alessandro Cadario
This paper presents a simulation environment and methodology for noise and vibration analyses of a driven rear axle in a bus application, with particular focus on medium to high frequency range (400 Hz to 3 kHz). The workflow demonstrates structure borne noise and sound radiation analyses. The fully flexible Multi–Body Dynamics (MBD) model - serving to cover the actual mechanical excitation mechanisms and the structural domain – includes geometrical contacts of hypoid gear in the central gear and planetary gear integrated at hubs, considering non-linear meshing stiffness. Contribution of aforementioned gear stages, as well as the propeller shaft universal joint at the pinion axle, on overall axle noise levels is investigated by means of sensitivity analysis. Based on the surface velocities computed at the vibrating axle-housing structure the Wave Based Technique (WBT) is employed to solve the airborne noise problem and predict the radiated sound.
2017-06-05
Technical Paper
2017-01-1800
Robert White
Several analytical tools exist for estimating a driveshaft’s critical speed, from simple elementary beam theory to sophisticated FEA models. Ultimately, nothing is better than a test, because no one will argue with the outcome from a well-designed measurement. Impact response measurements are easy, but they tend to over predict the critical speed. A test which sweeps the shaft speed up until failure is telling, but the speed causing failure is strongly dependent on even small amounts of variation in rotor unbalance. Waterfall plots of shaft displacement measurements offer the best indication of critical speed, however sometimes the resonance isn’t clearly seen or multiple resonances exist, making the critical speed unclear. A method less susceptible to system variation is offered here, fitting shaft orbit measurements to the theoretical single degree of freedom equation.
2017-06-05
Technical Paper
2017-01-1808
Francis Nardella
In a previous report, it was shown that power transmission through the camshaft reduced the first mode natural frequency of the powertrain and translated its convergence with dominant engine excitatory harmonics to a lower engine speed resulting in a marked reduction in torsional vibration for geared 6 cylinder compression ignition engines for aviation. This report describes a sweep though 2 and 4 stroke engines with differing numbers of cylinders configured as standard gear reduction (SGRE) and with power transmission through the camshaft (CDSE). Four and 6 cylinder engines were modeled as opposed boxer engines and 8, 10 and 12 cylinder engines were modeled as 180-degree V-engines. Mass-elastic models of the different engine power train configurations were modeled using the torsional vibration module in Shaft Designer obtained from SKF (Svenska Kullagerfabriken). Crankshaft, camshaft, gearing, pistons, piston pins and connecting rods with bolts were modeled in Solidworks.
2017-06-05
Technical Paper
2017-01-1856
Junji Yoshida, Koki Tanaka, Rie Nakamoto, Ken Fukasawa
Operational transfer path analysis (TPA) is one of TPA methods recently developed. This method calculates contributions of reference points (e.g., engine mount) to the response point (e.g., vehicle interior noise/vibration) using only the operational data. Through this operational TPA (OTPA), effective noise/vibration reduction can be achieved. On the other hand, many accurate vibraton modes can be obtained recently by the progress of CAE technique. However, it is not eacy to find out which calculated vibration modes of the structure (e.g., vehicle flame) affect the response point (e.g., steering) largely. In this study, we then combined the OTPA technique with CAE to obtain high contributing mode. As the test structure, a rear flame of a small constraction machine model was employed. Firstly, the vibration modes were obtained by CAE (eigenmode analysis) and 25 modes were obtaiend under 250 Hz. Subsequently, operational vibration of the structure was measured.
2017-06-05
Technical Paper
2017-01-1804
Chulwoo Jung, Hyeon Seok Kim, Hyuckjin Oh, Kwang Hyeon Hwang, Hun Park
An efficient method to determine bush stiffness of passenger cars for satisfying requirement of noise and vibration is developed. In general, a passenger vehicle includes various types of bush to connect systems and control forces (loads) transferred between systems which affect characteristics of noise and vibration of the vehicle. Noise and vibration of a vehicle are mainly caused by forces from power train (engine and transmission) and road excitation. While a vehicle is in operation, road excitation is applied to the vehicle through bushes. If a bush transfers less force to the body structure, levels of noise and vibration will be decreased. In other words, it is necessary to well determine characteristics of bushes when developing passenger vehicles. Bush stiffness is one of key factors to affect the performance of noise and vibration of the vehicle.
2017-06-05
Technical Paper
2017-01-1826
Sagar Deshmukh, Sandip Hazra
Engine mounting system maintains the position of power train in the vehicle with respect to chassis and other accessories during inertia, torque reaction loads and roadway disturbances. The mounting system also plays a role in terms of isolation of the rest of the vehicle and its occupants from power train and helps in maintaining vehicle ride and handling condition. This paper investigates the performance comparison between a conventional mount, hydromount and switchable hydromount during idle condition and ride performance. The optimization scheme aims to improve the performance of the mounting system in order to achieve overall power train performance and NVH attribute balancing through semi active technology. Keywords: Engine Mount, NVH,Switchable Hydromount
2017-06-05
Technical Paper
2017-01-1859
Filip Franek, Jungu Kang, Jeon Uk, Sunguk Choi
Abstract: Structure-born vibrations are often required to be localized in a complex structure, but in such dispersive medium, the vibration wave propagates with speed dependent on frequency. This property of solid materials causes an adverse effect for localization of vibrational events. The cause behind such phenomena is the propagating wave envelope that changes its phase delay and amplitude in time and space as it travels in dispersive medium. This problem was previously approached by filtering a signal to focus on frequencies of the wave propagating with similar speed, what improved accuracy of cross-correlation results. However, application of this technique has not been researched for localization of vibrational sources by a localization technique. In this work we take advantage of filtering prior to cross-correlation calculation while using multiple sensors to indicate approximate location of vibration sources.
2017-06-05
Technical Paper
2017-01-1863
Bhaskar Avutapalli, Mayuresh Pathak, Shalini Solipuram, Ken Buczek, Aaron Lock
Road noise and speech intelligibility are becoming ever more important, irrespective of the vehicle size, due to vehicle refinement as well as connectivity with mobile phones. With better aerodynamic designs, development of refined powertrains, and a tectonic shift from I.C. engine to electric motors, road noise will play an influential role for the customer. This paper describes the efforts undertaken to identify the road noise paths and develop countermeasures for a compact SUV vehicle. A hybrid test / CAE approach was followed to improve road noise performance of this vehicle. This effort involved creating tire models from physical hardware, creating synthesized road-load input from data taken on roads. Significant efforts were made to ensure model quality; focus on performing component level tests like bushing / damper characterization at high frequencies, modal correlation, IPI, NTF, and measurement of noise levels due to road input all ensured a high fidelity model.
2017-06-05
Technical Paper
2017-01-1892
Yosuke Tanabe, Masanori Watanabe, Takafumi Hara, Katsuhiro Hoshino, Akira Inoue, Masaru Yamasaki
Predicting vibration of motor gearbox assembly driven by a PWM inverter in an early development stage is demanding, because the assembly is one of the dominant noise sources of electric vehicle (EV). In this paper, we propose a simulation model that can predict the transient vibration excited by gear meshing, reaction force from mount and electromagnetic forces including carrier frequency component of inverter up to 10 kHz. By employing the techniques of structural model reduction and state space modeling, the proposed model enables to predict the vibration of assembly in operating condition to simulate with a system level EV simulator. A verification test was conducted to compare the simulation result with running test result of EV. Although the absolute value of simulation is 10 dB different from test at most, we conclude that the model can well predict the trend of the dominant order vibration caused by the electromagnetic force of motor including the carrier frequency of inverter.
2017-06-05
Technical Paper
2017-01-1780
Yong Xu
Research Objective: For MT vehicles, gearbox rattle is a common NVH problem which influences the comfort level of vehicle. In order to prevent rattle in the design phase of vehicle, this work aimed to study the excitation mechanism and influence factors of gearbox rattle, and then to propose effective measures. Methodology: First, the root cause of gearbox rattle problem was studied with the aid of classical dynamical theories. And then the simulation model of vehicle powertrain system was built via Matlab-Simulink. Then some critical parameters of the model and some experiential optimum proposals were selected to perform a sensitivity analysis on the torsional vibration, which is the root cause of rattle. Referring the simulation results, the dual-mass flywheel was selected as the most effective solution to gearbox rattle. Results: The simulation results indicated the critical parameters for optimization to prevent gearbox rattle problem in the design phase of the vehicle.
2017-06-05
Technical Paper
2017-01-1768
Yong Xu
Purpose: For rear-wheel-drive (or all-wheel-drive) vehicles, the vibration and noise that caused by driveshaft often become the main factors that influence the comfort level of vehicle. In order to control and improve the NVH problems related to driveshaft, this work aimed to study the excitation mechanism and transfer path of driveshaft vibration, and then to propose effective measures. The purpose of this work was to propose an effective way to improve the NVH performance by controlling the additional excitation force of U-joints in the early phase of project. Methodology: First, the rotation order characteristics of driveshaft were studied with the aid of classical dynamics. Then a rigid-elastic coupling model of vehicle powertrain was modelled with the theory of multi-body dynamics. By inputting the actual vehicle parameters into the model, the acceleration operation of vehicle could be simulated.
2017-06-05
Technical Paper
2017-01-1781
Joshua Wheeler
Automatic Speech Recognition (ASR) and Hands Free Communication (HFC) capabilities have become prominent in the automotive industry, with over 50% of new vehicle sales equipped with some level of ASR system. With the common use of mobile personal assistants and smartphones with Bluetooth capability, customer expectations for built in ASR and HFC systems have increased significantly. The performance of these ASR and HFC systems are highly dependent on the level of background or “masking” noise that competes with the speech engine’s ability to correctly convert the driver’s speech to actionable commands. HVAC noise provides high amplitudes of broadband frequency content that affects the signal to noise ratio (SNR) within the vehicle cabin, and works to mask the user’s speech. Furthermore, when the airflow from the panel or defroster vents are directed toward the vehicle microphone, a mechanical “buffeting” phenomenon occurs that distresses the ASR system even further.
2017-06-05
Technical Paper
2017-01-1864
Joshua Wheeler
Automatic Speech Recognition (ASR) and Hands Free Communication (HFC) capabilities have become prominent in the automotive industry, with over 50% of new vehicle sales equipped with some level of ASR system. With the common use of mobile personal assistants and smartphones with Bluetooth capability, customer expectations for built in ASR and HFC systems have increased significantly. The performance of these ASR and HFC systems are highly dependent on the level of background or “masking” noise that competes with the speech engine’s ability to correctly convert the driver’s speech to actionable commands. HVAC noise and environmental noise (like road and wind noise) provide high amplitudes of broadband frequency content that affects the signal to noise ratio (SNR) within the vehicle cabin, and work to mask the user’s speech. Managing this noise is a vital key to building a vehicle that meets the customer’s expectations for ASR and HFC performance.
2017-06-05
Technical Paper
2017-01-1893
Douglas Moore
This paper will examine the regulatory development process, discuss the technical principles of the Economic Commission for Europe (ECE), ECE R51.03 test, and discuss the overall objectives of the ECE R51.03 noise emission regulation. The development of this global noise emission regulation was a multi-stakeholder process which has resulted in new test procedures and new noise emission regulation principles. New test procedures based on ISO 362-1:2015 move the test basis to representative in-use noise emission, independent of vehicle propulsion technology. As part of the regulatory development, a monitoring program was conducted by the European Union to assess the applicability of the proposed test to provide representative vehicle noise emission results. The monitoring results also provided the basis to determine equivalent stringency between the test procedures of ECE R51.02 and R51.03.
2017-06-05
Technical Paper
2017-01-1803
John Van Baren
The accumulated damage that a product experiences in the field due to the variety of vibration stresses placed upon it will eventually cause failures in the product. The failure modes resulting from these dynamic stresses can be replicated in the laboratory and correlated to end use environment to validate target reliability requirements. This presentation addresses three fundamental questions about developing accelerated random vibration stress tests. Question#1: What random profile is needed (and for how much time) to accurately simulate the end use environment over the life-cycle of my product? Question #2: My product operates in many different vibration environments, how can I confidently combine them into one accelerated test?Question #3: How can I use the FDS to accelerate my test?
2017-06-05
Technical Paper
2017-01-1891
Todd Freeman, Kelby Weilnau
Similar to the automotive industry, the expectations from customers for the noise and vibration performance of personal vehicles such as golf carts, ATV’s, and side-by-side vehicles has continued to evolve. Not only do customers expect these types of vehicles to be more refined and to have acoustic signatures that match the overall performance capabilities of the vehicle, but marketing efforts continue to focus on product differentiators which can include the acoustic and vibration performance. Due to this increased demand for acoustic and vibration performance, additional NVH efforts are often required to meet these expectations. This paper provides a sample of some of the efforts that have occurred to further refine and develop the noise and vibration signature for golf carts.
2017-06-05
Technical Paper
2017-01-1817
Steven M. Gasworth, Vasudev Nilajkar, Matteo Terragni
Polycarbonate (PC) glazing as a one-for-one glass replacement offers a 50% weight reduction, but exhibits several dB lower sound transmission loss (STL) in the low frequency range where tire and engine noise are dominant. In the high frequency range where wind noise is dominant, PC glazing offers an STL at least comparable to its glass counterpart, and an STL exceeding glass when this frequency range encompasses the glass coincidence frequency. However, a key value proposition of PC glazing is the opportunity for feature integration afforded by the injection molding process generally used for forming such glazing. Two component (2K) molding fuses a second shot of plastic material behind, and along the perimeter of, the transparent PC first shot. This second shot can incorporate features and implement functions that require additional components attached or peripheral to a glass version.
2017-06-05
Technical Paper
2017-01-1870
Saeed Siavoshani, Prasad Balkrishna Vesikar, Daniel Pentis, Rajani Ippili
The objective of this paper is to develop a robust methodology to study the internal combustion (IC) engine block vibrations and to quantify the contribution of combustion pressure loads and inertial loads (mechanical loads) to the engine block vibrations. This study is not extended to the sound pressure generated by the engine and contribution analysis for that response. In an IC engine, the combustion and mechanical/inertial loads are the main sources of engine block vibrations. They both contain not only strong harmonic content due to their repetitive nature but also transient broadband impact loads. Therefore, it is difficult to identify/separate the contribution of combustion and inertial loads in the vibration response due to their correlated frequency excitations. One of the tools utilized in the industry to separate the combustion and mechanical noise is the Wiener filter.
2017-06-05
Technical Paper
2017-01-1802
Dong chul Lee, Insoo Jung, Jaemin Jin, Stephan Brandl, Mehdi Mehrgou
Classical approaches to development require a lot of time and cost to make samples involved the major design factors, which is why there have been recent researches to improve the efficiency of the development through a variety of simulation techniques. NVH simulation is of importance in this advanced phase, the design of all the parts should be satisfactory from the NVH point of view during the first phase of the project. This paper presents such an approach of simulation for the prediction radiated noise from a diesel engine with integrated powertrain model with changing combustion excitation. For changing combustion excitation, the cylinder pressure is measured and used as an input for simulation. The simulation model is validated with comparing the result of experiment in specified frequency ranges that the level of the noise is made louder than the development target.
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