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The golf market has remained flat in North America. Whereas, it has grown worldwide. A trend is seen where the number of young adults and adults over the age of 65 years involved with the game has increased. The demographics in golf showing the most growth also have high standards for the operation of the golf car. They have transcended their expectations to align with some of the qualities expected of automobiles. There is a shift in consumer expectations. Moreover, the market competition has also increased. This drives the OEMs to deliver refined golf cars with NVH being a key aspect in development. This paper showcases a recent study to improve the powertrain N&V performance of an internal combustion engine golf car. Primarily, a test-based approach is followed. Chassis rolls and on road testing are performed for benchmarking and target setting. System and component tests are performed to root cause issues.

This paper presents a study and comparison of two methods commonly used to treat unwanted vibration in vehicles. Laboratory work was done to measure and compare the effectiveness of common designs for practical tuned mass dampers (TMDs) and particle dampers under a wide range of conditions. The relative strength and weaknesses of the two approaches are compared in their abilities to treat vibration in a system due to resonant modes and forced response. The effectiveness of each method is investigated as a function of the weight of the treatment, amplitude and temperature effects.

Once the design of a door sheetmetal and accessories is confirmed, the acoustics of the door system depends on the sound package assembly. This essentially consists of a watershield which acts as a barrier and a porous material which acts as an absorber. The acoustical performance of the watershield and the reverberant sound build-up in the door cavity control the performance. This paper discusses the findings of a design study that was developed based on design of experiments (DOE) concepts to determine which parameters of the door sound package assembly are important to the door acoustics. The study was based on conducting a minimum number of tests on a five factor - two level design that covered over 16 different design configurations. In addition, other measurements were made that aided in developing a SEA model which is also compared with the findings of the results of the design study.

Recently, many authors have attempted to represent an automobile body in terms of experimentally derived frequency response functions (FRFs), and to couple the FRFs with a FEA model of chassis for performing a total system dynamic analysis. This method is called Hybrid FEA-Experimental FRF method, or briefly HYFEX. However, in cases where the chassis model does not include the bushing models, one can not directly connect the FRFs of the auto body to the chassis model for performing a total system dynamic analysis. In other cases when the chassis model includes the bushings, the bushing dynamic rates are modeled as constant stiffness rather than frequency dependent stiffness, the direct use of the HYFEX method will yield unsatisfactory results. This paper describes how the FRF's of the auto body and the frequency dependent stiffness data of the bushings can be combined with an appropriate mathematical formulation to better represent the dynamic characteristics of a full vehicle.

Ford introduced a new in-line 4-cylinder 2.3L DOHC 16-valve engine in its European D-class Scorpio vehicle. The engine is based on the proven 2.0L-DOHC engine with 8 or 16 valves. The new engine replaces the 2.0L DOHC 8-valve version. Primary focus of the development of this new 2.3L engine was on the noise and vibration improvement, both for the engine and for the vehicle interior noise. One measure to achieve this target was the application of balance shafts. In this paper, the development of the new engine will be described from the design stage to the production version. It will focus on the design of the balance shaft housing and all relevant engine NVH features. The various stages of the design and detailed optimization are explained. The NVH prediction by CAE methods is verified with experimental results. The influence of optimized components like the oil pan, front cover and the chain tensioner on the noise behavior will be discussed.

The Frequency Response Function (FRF) is a fundamental component to identifying the dynamic characteristics of a system. FRF's have a significant impact on modal analysis and root cause analysis of NVH issues. In most cases the FRF can be easily measured, but there are instances when the measurement is unobtainable due to spatial constraints. This paper outlines a simple experimental method for obtaining a high quality input-output FRF of a structure in areas where an impact hammer can not reach during impact testing. Traditionally, the FRF in such an area is obtained by using a load cell extender with a hammer impact excitation. A common problem with this device is a double hit, that yields unacceptable results.

The popularity of AWD passenger vehicles presents a challenge to provide car-like drive-train NVH within a relatively small package space. This paper describes a drive-train NVH case study in which analysis and test were used, in conjunction, to solve an NVH problem. Also, it details a systematic process of using the analytical model to identify and resolve similar problems. The particular problem for this case study is a noise and vibration issue occurring at 75 MPH primarily in the middle seat of an all-wheel drive vehicle. Tests indicated that it may be due to propeller shaft imbalance. Analysis results showed good correlation with the tests for that loading condition. Several solutions were identified, which were confirmed by both test and analysis. The most cost-effective of these solutions was implemented.

Based on NVH tests conducted on a heavy-duty turbocharged DI diesel engine, noise relevant differences between steady-state and transient operating condition were investigated. A vehicle drive-by test simulating the effects of vehicle mass and inertia was performed, followed by transient NVH measurements in a semi-anechoic test cell. Steady-state noise was exceeded by 5 dBA during transient operation due to broadband increase of noise excitation combined with structure resonance amplification. Transient noise results mainly from “harsher” combustion as a consequence of enlarged ignition delay indicated by significant increase in maximum cylinder pressure gradient. Variation of geartrain excitation and combustion excitation revealed that geartrain noise is of minor importance in this context.

Cavity reinforcement materials are used in the automotive industry to stiffen hollow cavities in vehicle body constructions. Typical areas of use include the engine rails, rocker panels, roof support or any other cavity in need of structural reinforcement. Use of these materials can allow for significant reductions in vehicle weight and increase structural stiffness with minimal impact to production tooling. Additional benefits can be gained by using the material as a physical barrier to the propagation of noise, water and dust. The objective of this paper is to describe a case study which implemented a new type of cavity reinforcing material to improve low frequency vehicle noise and vibration characteristics.

Customer requirements for quiet and more comfortable vehicles have steadily increased. Requirements for lightweight vehicle designs and the need for more fuel efficient engines are often contradictory to the customer expectations for NVH refinement. The driveline can be a significant source of NVH issues in the vehicle. The increasing complexity of modern driveline systems as well as the existence of several variants in the driveline architecture (front wheel, rear wheel and four-wheel/all-wheel drive, automatic-, manual-, automatic-shifted manual transmission, etc.) can make the driveline integration task very challenging. Due to the multitude of driveline components and potential driveline excitations sources, several driveline-related noise and vibration problems within different frequency ranges have to be understood and controlled to ensure a well refined vehicle.

NVH refinement is an important aspect of the powertrain development and vehicle integration process. The depletion of fossil-based fuels and increase in price of gasoline have prompted most vehicle manufacturers to embrace propulsion technologies with varying degrees and types of hybridization. Many different hybrid vehicle systems are either on the market, or under development, even up to all-electric vehicles. Each hybrid vehicle configuration brings unique NVH challenges that result from a variety of sources. This paper begins with an introductory discussion of hybrid propulsion technologies and associated unique vehicle NVH challenges inherent in the operation of such hybrid vehicles. Following this, the paper outlines a two-dimensional landscape of typical customer vehicle maneuvers mapped against hybrid electric vehicle (HEV) operational modes.

NVH refinement is an important aspect of the powertrain development process. Powertrain NVH refinement is influenced by overall sound levels as well as sound quality. The sound quality and hence the level of powertrain NVH refinement can be negatively affected by the presence of excessive impulsive noise. This paper describes a process used to develop an understanding of impulsive powertrain noise. The paper begins with an introductory discussion of various sources of impulsive noise in an automotive powertrain. Following this, the paper outlines a process for identifying the source of the impulsive powertrain noise using examples from case studies. The remainder of the paper focuses on certain examples of impulsive noise such as Diesel knocking noise, injector ticking, impulsive cranktrain noise, and gear rattle. For these examples, the development of key objective metrics, optimization measures, and improvement potential are examined.

Knowledge of the loads experienced by a leaf spring suspension is required for the optimal design of the suspension components and frame. The most common method of representing leaf springs is the SAE 3 link model, which does not give good results in the lateral direction. In this paper, a beam element leaf spring model is developed. This model is validated using data obtained from laboratory tests done on leaf spring assemblies. The model is then subjected to actual road load data measured on the Proving Ground. Lastly, results from the beam element model are presented and compared with results obtained from proving ground tests. Overall, the beam element model gives good results in all directions except in situations where it is subjected to high fore/aft acceleration and high reverse braking events.

Mode management is an essential part of the design process for NVH performance. System resonances must be sufficiently separated to minimize interaction from source inputs and each other [1]. Such resonances are typically determined through experimental modal testing conducted in a lab environment under controlled and repeatable conditions. Global vehicle and suspension system response demonstrate soft nonlinear behavior, however. Their resonant frequencies may thus decrease under on-road input not reproducible in a lab environment. Subsequently, mode management charts derived from lab testing may not be representative of the vehicle's on-road dynamic response. This paper presents modal model determination methodologies, and examines suspension system and vehicle global dynamic response under lab modal test and operating conditions. Vehicle suspension modes measured under static and dynamic (rolling) conditions will be compared.

One of the major NVH concerns for automobile manufacturers is the response of a vehicle to the impact of the tire as it encounters a road discontinuity or bump. This paper describes methods for analyzing the impact response of a vehicle to such events. The test vehicle is driven on a dynamometer, on which a bump simulating cleat is mounted. The time histories of the cleat impact response of the vehicle can be classified as a transient and a repeated signal, which should be processed in a special way. This paper describes the related signal processing issues, which include converting the time data into a continous spectrum, determination of the correct scaling factor for the analyzed spectrum, and smoothing out harmonics and fluctuations in the signal. This procedure yields a smooth frequency spectrum with a correctly scaled amplitude, in which the frequency contents can be easily identified.

Combustion noise plays a considerable role in the acoustic tuning of gasoline and diesel engines. Even though noise levels of modern diesel engines reach extremely low values, they are still higher than those of conventional gasoline engines. On the other hand, new combustion procedures designed to improve fuel consumption lead to elevated combustion noise excitations as in case of today's direct injecting gasoline engines whose vibration excitation and airborne noise emissions are slightly increased during stratified operation. The partly conflicting development goals resulting from this can only be realized by integrating the NVH specialists' expertise into every development step from concept to SOP.

The concept of using tuned mass dampers and absorbers to address undesirable vibration responses in vehicles is not new. However, there are several design issues that cause the vibration control performance of real life tuned dampers to be significantly less than that predicted by simple 2-DOF theory. In this paper, the authors will review tuned damper design theory. Practical issues regarding the use of real life elastomers as spring elements are reviewed, including temperature sensitivity, material damping and nonlinearity. Various elastomers are compared for their effectiveness and applicability to the typical automotive environment. Rules of thumb for tuned damper design are discussed including locations for placement of dampers in automotive structures, tuning for temperature variations, determining the needed mass, and measurements and simulations that can greatly improve the success and timing for tuned damper design.

As vehicle development cycles become more condensed, it is necessary to perform testing as expeditiously as possible. One way to accomplish this is to perform tests previously performed over the road in a controlled laboratory environment. The Noise and Vibration engineering consulting group, a division of Roush Industries, Inc. has recently commissioned a four-wheel drive chassis dynamometer located in a hemi-anechoic test cell in order to provide manufacturers and tier suppliers a faster alternative to over the road noise and vibration vehicle level testing. As a consulting company that supports a wide variety of vehicle development needs, many unique challenges had to be overcome throughout the design and construction process. This paper identifies these challenges and presents a methodology for designing and constructing a facility to meet the broad purpose of supporting the noise and vibration testing requirements of the automotive industry.

This paper dis cusses the development of a nonlinear shock absorber model for low-frequency CAE-NVH applications of body-on-frame vehicles. In CAE simulations, the shock absorber is represented by a linear damper model and is found to be inadequate in capturing the dynamics of shock absorbers. In particular, this model neither captures nonlinear behavior of shock absorbers nor distinguishes between compression and rebound motions of the suspension. Such an inadequacy limits the utility of CAE simulations in understanding the influence of shock absorbers on shake performance of body-on-frame vehicles in the low frequency range where shock absorbers play a significant role. Given this background, it becomes imperative to develop a shock absorber model that is not only sophisticated to describe shock absorber dynamics adequately but also simple enough to implement in full-vehicle simulations. This investigation addresses just that.

It is important to develop powertrain NVH characteristics with the goal of ultimately influencing/improving the in-vehicle NVH behavior since this is what matters to the end customer. One development tool called dB(VINS) based on a process called Vehicle Interior Noise Simulation (VINS) is used for determining interior vehicle noise based on powertrain level measurements (mount vibration and radiated noise) in combination with standardized vehicle transfer functions. Although this method is not intended to replace a complete transfer path analysis and does not take any vehicle specific sensitivity into account, it allows for powertrain-induced interior vehicle noise assessments without having an actual test vehicle available. Such a technique allows for vehicle centric powertrain NVH development right from an early vehicle development stage.