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Technical Paper
2014-04-01
Pragadish Nandakumar
The fuel prices are increasing every day and so are the pollution caused by vehicles using fossil fuels. Moreover, in a car with an internal combustion engine, we get on average 25% efficiency, the other 75% is wasted, mostly through friction and heat. One important loss is the dissipation of vibration energy by shock absorbers in the vehicle suspension under the excitation of road irregularity and vehicle acceleration or deceleration. In this paper we design, manufacture and test a regenerative coil-over strut that is compact, simple in design and more economical. Since our strut is a modification of an existing strut design, it would be much more feasible to implement. We tested our prototype strut using a TATA Indica car under city road conditions. The damping characteristics and output voltage of the strut were recorded and compared with a normal coil over strut. Based on the test data, it was found that the strut was able to recover about 8-10 watts of electricity at 20kmph.
Technical Paper
2014-04-01
Marcus Becher, Stefan Becker
Abstract This paper focuses on the applicability of numerical prediction of sound radiation caused by an axial vehicle cooling fan. To investigate the applicability of numerical methods, a hybrid approach is chosen where first a CFD simulation is performed and the sound radiation is calculated in a second step. For the acoustic simulation an integral method described by Ffowcs-Williams-Hawkings is used to predict the sound propagation in the far-field. The simulation results are validated with experiments. The corresponding setup in experiments and simulation represents an overall system which includes the cooler, the cooling fan and a combustion engine dummy. To optimize the economical applicability in terms of simulation setup and run time, different approaches are investigated. This includes the simulation of only one blade using a periodic boundary condition as compared to the whole fan geometry. In the CFD simulation an SAS-turbulence-model is applied. The results show that this is a very useful approach considering the challenges in prediction of numerical sound.
Technical Paper
2014-04-01
Manchi Venkateswara Rao, Jos Frank, Prasath Raghavendran
Abstract Accurate quantification of structure borne noise is a challenging task for NVH engineers. The structural excitation sources of vibration and noise such as powertrain and suspension are connected to the passenger compartment by means of elastomer mounts and spring elements. The indirect force estimation methods such as complex dynamic stiffness method and matrix inversion method are being used to overcome the limitations of direct measurement. In many practical applications, the data pertaining to load dependent dynamic stiffness of the connections especially related to mounts is not available throughout the frequency range of interest which limits the application of complex dynamic stiffness method. The matrix inversion method mainly suffers from the drawback that it needs operational data not contaminated by the effect of other forces which are not considered for calculation. In this paper, a new method is proposed in which the structure borne noise associated with powertrain is quantified easily and reliably.
Technical Paper
2014-04-01
Ajo John Thomas, Avnish Gosain, Prashanth Balachandran
Abstract The automobile market is witnessing a different trend altogether - the trend of shifting preference from powerful to fuel efficient machines. Certain factors like growing prices of fuel, struggling global economy, environmental sensitiveness and affordability have pushed the focus on smaller, efficient and cleaner automobiles. To meet such requirements, the automobile manufacturers, are going stringent on vehicle weights. Using electric and hybrid power-plants are other options to meet higher fuel efficiency and emission requirements but significant cost of these technologies have kept their growth restricted to only few makers and to only few regions of the globe. Optimizing the vehicle weight is a more attractive option for makers as it promises lesser time to market, is low on investment and allows use of existing platforms. However, lightweighting and NVH often conflict each other in vehicle development and hence design optimization plays a vital role in assigning a tradeoff between the lightweighting and NVH.
Technical Paper
2014-04-01
Hangsheng Hou
Abstract The purpose of this work is to analytically investigate automotive exhaust system noise generation and propagation phenomena. The turbulent exhaust gas flow interacts with the exhaust system structure, and as a result of this interaction, the structure vibrates and radiates noise. In the meantime, pressure wave becomes acoustic wave at its outlet. This study focuses on an exhaust system and carrying out transient fluid-structure analysis by using an explicit finite element solver that is capable of solving the Navier Stokes equations for turbulent, compressible viscous fluids as well as the field equations for solid structures in a fully coupled fashion. The time domain signals obtained from the transient analysis are post-processed to yield frequency domain data, sound pressure levels, noise source pattern as well as the selected acoustic field contour snapshots. The work involves evaluating different design proposals and comparing their corresponding sound pressure levels and acoustic fields.
Technical Paper
2014-04-01
Vijay Antony John Britto, Kalyankumar Sidram Hatti, Sai Sankaranarayana, Sivasankaran Sadasivam, Ekambaram Loganathan
Abstract Commercial vehicle NVH attributes primarily focus on interior noise for driver's comfort and exterior noise for environmental legislation. Major sources for both the interior and exterior noise are power train unit, exhaust and air intake system. This paper focuses on development of Air Intake System (AIS) for better interior and exterior NVH performance for medium and heavy commercial vehicles. For air intake system, structural radiations from its panels and nozzle noise are significant contributors on overall vehicle NVH. Noise generation mechanism in air intake system occurs due to opening and closing of the valves and inlet air column oscillation by sharp pressure pulse from cylinder. Based on benchmarking, vehicle level targets have been arrived, and then cascaded to system and sub-system level targets. For air intake system, targets for nozzle noise at wide open throttle condition have been set for exterior NVH performance. These targets are further cascaded down to transmission loss (TL), snorkel breathing mode, isolation & dynamic stiffness attributed for improvement in interior/exterior noise and sound quality.
Technical Paper
2014-04-01
Masashi Terada, Takashi Kondo, Yukihiro Kunitake, Kunitomo Miyahara
Abstract In automobile development, steering vibrations caused by engine excitation force and suspension vibration input from the road surface are a problem. The conventional method of reducing vibrations and thereby securing marketability has been to dispose a dynamic damper inside the steering wheel. The resonance frequency of a steering system varies for each vehicle developed (as a result of the vehicle size, the arrangement of the stiff members of the vehicle body, and the like). As a result, the individual values of dynamic dampers that are used with vehicles must be adjusted for each developed vehicle type. To address this problem, we have developed a new structure in which, rather than using a conventional dynamic damper, we disposed a floating bush on the Supplemental Restraint System (SRS) module attachment section and used the SRS module itself as the weight for the dynamic damper. In this structure, the dynamic damper weight is approximately eight times greater than the conventional weight, the vibration reduction effect is enhanced, and the effective frequency range is widened.
Technical Paper
2014-04-01
Todd Tousignant, Kiran Govindswamy
Abstract Increased customer expectation for NVH refinement creates a significant challenge for the integration of Diesel powertrains into passenger vehicles that might have been initially developed for gasoline engine applications. A significant factor in the refinement of Diesel powertrain sound quality is calibration optimization for NVH, which is often constrained by performance, emissions and fuel economy requirements. Vehicle level enablers add cost and weight to the vehicle and are generally bounded by vehicle architecture, particularly when dealing with a carry-over vehicle platform, as is often the case for many vehicle programs. These constraints are compounded by the need to make program critical sound package content decisions well before the availability of prototype vehicles with the right powertrain. In this paper, a case study on NVH development for integration of a light duty Diesel powertrain is presented. A process, based on a time-domain transfer path methodology was applied to provide focused engineering development of powertrain and vehicle level NVH enablers.
Technical Paper
2014-04-01
Cha-Sub Lim, Eunjun Han, Chahe Apelian, David Bogema
A new approach to achieve better customer perception of overall vehicle quietness is the sound balance improvement of vehicle interior sound during driving. Interior sound is classified into 3 primary sound source shares such as engine sound relative to revolution speed, tire road noise and wind noise relative to vehicle speed. Each interior sound shares are classified using the synchronous time-domain averaging method. The sound related to revolution order of engine and auxiliaries is considered as engine sound share, tire road noise and wind noise shares are extracted by multiple coherent output power analysis. Sound balance analysis focuses on improving the relative difference in interior sound share level between the 3 primary sound sources. Virtual sound simulator which is able to represent various driving conditions and able to adjust imaginary sound share is built for several vehicles in same compact segment. Objective sound evaluation targeting the North American customer is carried out using the virtual sound simulator tool in audio lab and it is verified that overall customer perception is improved by modification of sound balance between 3 primary sound shares.
Technical Paper
2014-04-01
Youichi Kamiyama
Abstract Tire cavity noise has long been one of the main road noise issues. Various ideas for devices to reduce tire cavity noise have been patented or discussed in technical reports, but many issues remain for commercialization, and at present only some tires have appeared as products. Therefore, technology was developed for mounting Helmholtz resonators on the wheels, enabling reduction of tire cavity noise without placing restrictions on the tires. The advantage of this technology is that the cost and productivity targets needed for mass production can be satisfied without impairing the tire and wheel functions. The aim of this development was to construct low-cost device technology that is well-suited to mass production and enables reduction of tire cavity noise to an inaudible sound pressure without adversely affecting dynamic product marketability such as strength and durability performance and handling performance. In order to realize that aim, the device configuration employed a structure that assembles separate thin, lightweight plastic resonators in the wheel well.
Technical Paper
2014-04-01
Meng Huang
A 2 DOF nonlinear dynamic model of the automotive wiper system is established. Complex eigenvalues are calculated based on the complex modal theory, and the system stability as well as its dependence on wiping velocity is analyzed. Bifurcation characteristics of frictional self-excited vibration and stick-slip vibration relative to wiping velocity are studied through numerical analysis. Research of nonlinear vibration characteristics under various wiping velocities is conducted by means of phase trajectories, Poincaré map and frequency spectrum. The pervasive stick-slip vibration during wiping is confirmed, and its temporal and spatial distributions are analyzed by way of time history and contour map. Duty ratio of stick vibration and statistics of scraping residual are introduced as quantitative indexes for wiping effect evaluation. Results indicate that the negative slop of frictional-velocity characteristic is the root cause of system instability. As the wiping velocity decreases, the vibration state transforms from periodic to quasi-periodic and then to chaos in both high and low velocity ranges.
Technical Paper
2014-04-01
Hyungtae Kim, Sehwun Oh, Ki-Chang Kim, Ju Young Lee, Jungseok Cheong, Junmoo Her
Abstract It is common knowledge that body structure is an important factor of road noise performance. Thus, a high stiffness of body system is required, and determining their optimized stiffness and structure is necessary. Therefore, a method for improving body stiffness and validating the relationship between stiffness and road noise through CAE and experimental trials was tested. Furthermore, a guideline for optimizing body structure for road noise performance was suggested.
Technical Paper
2014-04-01
Wei Yang, Wenku Shi, Chunxue Chen
Aiming at the abnormal vibration of driver seat of a passenger car in idle condition, vibration acceleration of engine, frame and seat rail was tested to identify vibration sources. Order tracking and spectrogram analysis indicated that the second order self-excitation of engine was the main cause. To solve the problem, semi-active controlled hydraulic engine mount with air spring of which characteristics could shift between a high dynamic stiffness and a low one was applied. Then the structure and principle of the mount with variable characteristics was introduced and control mode was analyzed. Dynamic characteristics were obtained by bench test. With sample mount applied, vibration of seat rail was tested again in multiple vehicle and engine working conditions. Dates showed that abnormal vibration in idle condition was extremely reduced and the mount could also meet the requirement of engine to dynamic stiffness in driving conditions.
Technical Paper
2014-04-01
Tamer Elnady, Mats Abom, Yong Yang
Exhaust noise is a major contributor to the radiated noise level of a vehicle, especially at idle. The radiated noise level has to meet a certain criteria based on regulation and consumer demand. In many cases, the problem appears after the vehicle is manufactured and the tailpipe noise measurement is performed indicating a high noise level that needs to be reduced. This paper describes one of those cases where the radiated noise level of a certain passenger car at idle was required to be reduced by 6 dB(A). The exhaust system consists of one main muffler and one auxiliary muffler. A 1D two-port model of the exhaust system including the two mufflers was built using commercial software. This model was validated against the measurement of the two-port matrix of both mufflers. The model was then used together with tailpipe noise measurements to estimate the characteristics of the source strength and impedance. Using a 1D model of the complete system, it was possible to propose several modifications for the vehicle manufacturer to choose from.
Technical Paper
2014-04-01
Atul Devidas Pol, Praveen Naganoor
Abstract Achieving targeted global modes (torsion, vertical bending and lateral bending) is one of the main enablers in meeting desired NVH performance characteristics of a new vehicle program. The torsion mode of next generation Land Rover - Freelander was lagging behind its target while the development cycle was quite progressed beyond underbody freeze. There was a challenge to recover more than 8 Hz in BIW torsion mode. A combination of Nastran Sol 200 (design sensitivity and optimization) and iterative process was adopted to demonstrate how the mode could be recovered with optimum mass penalty to the program. The paper states the existing modal status when this work was taken up. Next it elucidates design sensitivity/optimization module outcome which identifies sensitive areas to improve torsion mode. Then it describes how feasible design solutions were developed while iterating using Nastran Sol 103 modal analysis, based on the outcome of above sensitivity/optimization analyses, to converge to the specified target.
Technical Paper
2014-04-01
Mohit Kohli, S Nataraja Moorthy, Manchi Venkateswara Rao, Prasath Raghavendran
Abstract The present quiet and comfortable automobiles are the result of years of research carried out by NVH engineers across the world. Extensive studies helped engineers to attenuate the noise generated by major sources such as engine, transmission, driveline and road excitations to a considerable extent, which made other noise sources such as intake, exhaust and tire perceivable inside. Many active and passive methods are available to reduce the effect of said noise sources, but enough care needs to be taken at the design level itself to eliminate the effect of cavity resonances. Experimental investigation of cavity resonances of real systems is necessary besides the FEA model based calculations. Acoustic cavity resonance of vehicle sub systems show their presence in the interior noise through structure borne and air borne excitations. Cavity resonances for some systems e.g. intake can only be suppressed through resonators. The exact location and nature of acoustic cavity resonance needs to be found as accurately as possible to bring out the best from a resonator.
Technical Paper
2014-04-01
Changxin Wang, Deguang Fang, Fuxiang Guo
Abstract To find out the main excitation sources of a bus floor's vibration, modal analysis and spectral analysis were respectively performed in the paper. First we tested the vibration modal of the bus's floor under the full-load condition, and the first ten natural frequencies and vibration modes were obtained for the source identification of the bus floor's vibration. Second the vibration characteristic of the bus floor was measured in an on-road experiment. The acceleration sensors were arranged on the bus's floor and the possible excitation sources of the bus, which includes engine mounting system, driveline system, exhaust system, and wheels. Then the on-road experiment was carefully conducted on a highway under the four kinds of test condition: in-situ acceleration, uniform velocity (90km/h, 100km/h, 110km/h, 120km/h), uniform acceleration with top gear, and stall sliding condition with neutral gear. After that, by performing order tracking analysis and spectral analysis, the 1st order rotation frequency of the driveline and the 2nd order frequency of engine were identified to be the main cause of bus floor's vibration.
Technical Paper
2014-04-01
Ravi Kiran Cheni, Chetan Prakash Jain, Revathy Muthiah, Srikanth Gomatam
Abstract Automotive OEMs quest for vehicle body light weighting, increase in Fuel efficiency along with significant cut in the emissions pose significant challenges. Apart from the effect on vehicle handling, the reduction of vehicle weight also results in additional general requirements for acoustic measures as it is an important aspect that contributes to the comfort and the sound quality image of the vehicle, thus posing a unique challenge to body designers and NVH experts. Due to these conflicting objectives, accurate identification along with knowledge of the transfer paths of vibrations and noise in the vehicle is needed to facilitate measures for booming noise dampening and vehicle structure vibration amplitude. This paper focuses on the application of a unique design and development of vehicle body structure anti-vibration dynamic damper (DD), unique in its aspect in controlling booming noise generated at a specific RPM range. Design methodology follows the concept of Mass-damper system on vehicle body or engine structure where panel with multi-degree of freedom vibrating at medium level frequency is transferred to damper which is vibrating at same resonant frequency in 180° opposite phase.
Technical Paper
2014-04-01
Xiaozhen Sheng, Shouhui Huang, Sheng Tian, Xia Cao, Youlin Huang
Abstract Subject to excitations from pressure pulsations in boost air, the rubber pipe connecting the turbo compressor outlet and the intercooler of an engine vibrates structurally and radiates noise. If the pipe is improperly selected, the resulted vibration may be strong enough to radiate noise which is sufficient to damage the sound quality of the vehicle. This paper presents an initial analysis on this issue. First, formulae are derived for predicting vibration and sound radiation of the pipe for a given pressure pulsation, resulting in sound transmission index for the pipe to quantify its sound insulation behavior. Then effects on the sound transmission index are investigated for pipe parameters such as pipe wall thickness, Young's modulus and density of pipe material.
Technical Paper
2014-04-01
Tomoya Ishii, Tomohiro Sudo, Masanori Morikawa, Daisuke Nagahata
Abstract General analysis methods which are known as Transfer Path Analysis and Air borne Source Quantification have been extended to estimate forces of an air conditioner's parts and also clarify the path from air conditioner system. These results show noise transfer path to be improved. Originally, the existing methods are known to require considerable amount of time for the cause of complicated measurement to get analysis results. In the work of this paper, required measurement is simplified, and time reduction of 50% is achieved without critical decrease in analysis accuracy.
Technical Paper
2014-04-01
Swapnil S. Kulkarni, Muragendra Magdum, Ravi B.
Abstract Automotive shock absorber shims are subjected to deformation while generating the pressure differential across the rebound and compression chambers. Considering the contact, large deflection, and material this shim stack deformation will be nonlinear throughout the working velocity of shock absorbers. The deformation of shim stack mainly depends on number and geometry of deflection disk, number and geometry of ports, and clamping disk geometry on which shims are rested. During the rebound and compression stroke of the shock absorber, the oil flows through the piston and base valve ports. High pressure oil developed during mid and high velocity of shock absorber results in deflection of shim stack in piston and base valve assembly. This deflection leads to oil leakage through the shim stack which results in change in damping force by the shock absorber. The fluid pressure from the flow passage (well) acting over surface area of shim differs while causing an elastic bending of the shims.
Technical Paper
2014-04-01
Manchi Venkateswara Rao, Jos Frank, Mohit Kohli
Abstract Brake groan noise is resolved without any major change in the design of brake system and vehicle sub-system components in the development phase of a utility vehicle. The groan noise is observed during the end of the stopping of the vehicle under moderate braking. The concerned NVH issue is perceived as unacceptable noise in the passenger compartment. Groan induced vibration is subjectively felt on steering and seat frame. A typical process is established to successfully reproduce the groan which helped in precisely evaluating the effect of modifications proposed. The temperature range of the disc which has the highest probability to produce the groan noise is found out experimentally. The transfer path analysis is carried out to find the path contributions from suspension. Acoustic transfer functions from considered paths are measured with the suspension removed from vehicle. Effects of addition of mass on various locations of suspension and stiffness change of suspension bushings are studied.
Technical Paper
2014-04-01
Gang Tang, Jinning Li, Chao Ding, Yunqing Zhang
Abstract This paper describes a simplified model to identify sprung mass using golden section method, the model treats the unsprung mass vertical acceleration as input and the sprung mass vertical acceleration as output, which can avoid the nonlinear influence of trye. Unsprung mass can be also calculated by axle load and the identified sprung mass. This study carries out road test on the vehicle ride comfort and takes a scheme that the group of 20 km/h is used to identify sprung mass and the group of 80 km/h is used to verify the identification result. The similarity of the results from the simulation and experiments performed are, for the sprung mass, 98.59%. A conclusion can be drawn that the simple method to measure the sprung mass in the suspension systems in used vehicles, such as the vehicle shown here, is useful, simple and has sufficient precision.
Technical Paper
2014-04-01
Meng Huang
A disc-pad system is established to study impacts of surface topography on brake squeal from the perspective of statistical analysis. Firstly, surface topographies of brake disc and pad are precisely measured on the scale of micron and are statistically analyzed with a three-dimensional evaluation system. Secondly, the finite element model of brake disc and pad without surface topographies is created and verified through component free modal tests. Thereby the valid brake squeal model for complex modal analysis is built with ABAQUS. An effective method is developed to apply interface topographies to the smooth contact model, which consequently establishes sixty brake squeal models with topographies. Thirdly, impacts of surface topography on brake squeal are studied through comparison and statistical analysis of prediction results with and without topographies. The analysis manifest that topography amplitudes and evaluation index deviations of brake pad far exceed those of the disc, indicating the surface of brake pad is relatively much rougher.
Technical Paper
2014-04-01
Kun Diao, Lijun Zhang, Dejian Meng
Abstract Brake squeal shows a significant uncertainty characteristic. In this paper, a series of bench tests were carried out to study the uncertainty of brake squeal on a multi-function brake inertia dynamometer test bench. Then based on time-frequency analysis results, a creative squeal confirmation and determination method was presented, which can show the squeal variations in the domains of time, frequency and amplitude together. An uncertainty analysis method was also established, in which the statistical parameters of squeal frequency and sound pressure level (SPL), and probability density evaluation of frequency based on Quantile-Quantile Plot (QQ plot) were given. And a judgment method of the frequency doubling was devised based on numerical multiple and occurrence concurrence, as well as the uncertainty statistical analysis method considering frequency doubling. All the methods established were applied to the uncertainty analysis of brake squeal. It was found that, both the squeal frequency and SPL are dispersed, and each squeal has its own statistical results.
Technical Paper
2014-04-01
HakSon Han, ChulMin Park, JeongHoi Heo, Sang Kyu Kang
Abstract In order to achieve the proper automobile interior sound, the tailpipe noise of the exhaust system must be considered as a main contributor. This paper describes a study of the achievement of dynamic sound quality through exhaust system design. Firstly, we determined the vehicle's interior sound quality and established a target sound using a subjective assessment of 10 benchmark vehicles. The exhaust noise target is determined by means of transfer path analysis focusing on the noise source and how it's impacted by the muffler design. The exhaust system is commonly modeled as a combination of source strength and impedance. We obtained the source character by the wave decomposition method using two microphones and six loads ultimately leading to an optimized design of the inner muffler structure. Based on this study, we achieved dynamic interior sound and improved exhaust system performance.
Technical Paper
2014-04-01
Kambiz Jahani, Sajjad Beigmoradi, Mohsen Bayani Khaknejad
Abstract The main objective of this study is to investigate the effect of spot-weld modeling approaches on NVH virtual simulation problems. For this purpose, finite element method is considered for further simulations. The goal is to evaluate and compare results within the domain of 0 to 200 Hz by modeling spot-welds with three different element types: a rigid body constraint element (RBE), two rigid body elements with hexahedral solid element (RBE3-HEXA-RBE3) and CWELD constraint. In order to evaluate the effects, three main NVH analyses are chosen for this study. In the first place, a free-free modal analysis is performed for the BIW and trimmed body models of a D-segment saloon car in order to estimate natural frequencies and mode shapes. Afterwards, a frequency response analysis is performed to evaluate the dynamic stiffness of engine mount. Finally, a noise transfer function (NTF) simulation is carried out to calculate the sound pressure level at driver ear's location. The out coming results from each type of simulations are extracted and compared to investigate the effect of spot-weld modeling on the accuracy of FEM analyses results concerning NVH problems.
Technical Paper
2014-04-01
Kyoung-Jin Chang, Ki Woong Jeong, Dong Chul Park
Abstract This paper describes a systematic approach to the development of a luxurious driving sound. In the first step, the luxurious sound is conceptualized through jury test, factor analysis and regression analysis. From the results, the main factors and the correlation equation for the luxurious sound are extracted. Also, customer's preference for the luxurious sound is investigated from the customer clinic. In the second step, three core axes and the detailed indices for luxurious sound are defined and quantified. These core axes are a dynamic sound character, a sound balance and a sound harmony. These core axes are also composed of detailed indices and quantified by guide lines. In the third step, each contribution of the sub-systems for sound quality is identified and the target values and methods for implementing the luxurious sound are suggested. In this process, noise path analysis and the customer's preference in each region are considered. Finally, the sound is developed by intake, exhaust and ECU tuning which have dominant contributions for the sound quality and verified with respect to each sales region.
Technical Paper
2014-04-01
Jin-Seok Hong, Hyung-Seok Kook, Kang-Duck Ih, Hyoung-Gun Kim
Abstract Fluctuation in the sound pressure level of the interior noise of an on-road vehicle is always caused by unpredictable factors such as wind gusts, traffic, roadside obstacles, and changing drive-by-drive conditions, and is hence, not reproducible in nature. Since the human brain is known to be more sensitive to noise that is amplitude-modulated than noise at a steady level [1], it is important to evaluate and improve the NVH performance of a vehicle in terms of the fluctuating interior noise likely to be experienced by drivers or users. To this end, an evaluation system was developed as part of this study, the details of which are presented in this paper. The system is composed of hardware for database storage and replay of sounds, and software for synthesizing the noise signals. For given wind tunnel test results, the evaluation system yields a wind noise model that can synthesize wind noise signals for any wind scenario. Additionally, the road and engine noise components can be extracted from proving ground or real road tests.
Technical Paper
2014-04-01
Takahito Watanabe, Takuya Yoshimura
Abstract In performing noise control design for vehicles, there is a benefit to identifying important vibro-acoustic coupled mode. The purpose of this study is “identifying the coupled mode of a vehicle through FRF (frequency response function) measurement”. A speaker which measure the internal acoustic pressure was used as a new experimental method. An acoustic input is estimated by the fluctuation of the acoustic pressure inside the speaker box. Acoustic pressures are measured by using some microphones, the vibrations of the structure are measured by using some accelerometers. Main experiment was carried out for measure the vibro-acoustic mode. First acoustic mode was identified in about 66 Hz. And structure associated mode with this mode was identified. Hence, the vibro-acoustic mode identification was carried out.
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