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Tire flat-spotting occurs when tires remain in a loaded condition without rolling for an extended period of time, and can be temporary or permanent depending on the length of storage, vehicle loading and environmental factors. Tire non-uniformity caused from flat-spots often induce shake and shimmy vibration in vehicles due to increased tire-wheel force variation input into the chassis. This results in increased warranty costs for OEMs and tire suppliers and customer dis-satisfaction in third-party quality surveys such as J. D. Power IQS. Flat-spotting is of particular concern for slow-moving vehicle inventory parked for long periods at plants and/or dealership lots. OEMs often stipulate or recommend inventory storage practices for dealers that require physical movement of vehicles at some set duration to reduce the risk of tires developing permanent flat-spots.

A high performance rigid airfoil profile sunroof wind deflector has been developed for high speed freeway driving with the sunroof open. This deflector is clearly superior to the conventional bar type deflector and less expensive compared to tall flexible fabric mesh deflectors applied on high end vehicles today. It provides superior speech intelligibility under high speed driving with sunroof open. The criterion for designing this deflector was to get the highest airspeed possible to span the sunroof opening under all conditions. The customized shape also utilizes flow unsteadiness, including those at the onset of buffeting, in order to condition the shear layer. The airfoil profiled deflector yielded superior mid and high frequency acoustic performance with acceptable low frequency performance. A shorter airfoil deflector was sufficient to keep the external airflow from entering the forward tilted sunroof opening on a mid-size SUV under test.

Recent trends in vehicle light-weighting and tire design requirements have created an increased awareness to tire flat-spotting. Tire flat-spotting occurs when tires remain in a loaded condition without rolling for an extended period of time. Tire flat-spotting can either be temporary or permanent depending on the length of storage and other environmental factors. Tire non-uniformity caused due to flat-spots often induces shake and shimmy (back and forth oscillation of steering wheel) vibration in vehicles due to increased tire-wheel force variation input into the chassis. This can result in increased warranty costs for OEMs (Original Equipment Manufacturers) as well as customer dissatisfaction exhibited in third party quality surveys like the annual J. D. Power IQS (Initial Quality Survey).

The fuel economy benefits of Continuously Variable Transmission (CVT) technology have led to a steady growth in their adoption since the 1990's that is likely to continue despite the competition from Dual Clutch Transmission (DCT) & Automated Manual Transmission (AMT) technology. Even though CVTs provide a smoother driving experience due to their “shift-free” operation, general market feedback indicates some level of consumer dissatisfaction in the area of acceleration sound quality. This is particularly evident in the sub-compact and compact vehicle segments that feature small four cylinder engines with cost/weight limited sound packaging. The dissatisfaction with the acceleration sound quality is primarily linked to the non-linear relationship between engine RPM and vehicle speed that is inherent to CVTs and is often referred to as “rubber-band” feel.

The advantages of hydraulic mounts over conventional elastomeric mounts for NVH refinement are well known, particularly in the area of engine and suspension mounts. Recently, hydraulic mounts have been successfully employed as body mounts between the frame and cab, principally to control freeway hop in pickup trucks. Due to their ability to provide increased damping at small displacements, hydraulic body mounts also have good potential to reduce smooth road shake. This paper documents the reduction in smooth road shake performance of a full size pickup truck. Hydraulic body mounts tuned to the frequency of the smooth road shake sensitivity area were added to the rearmost cab mount location. Both tire-wheel balance and uniformity were set to the highest production level specification allowed and the effect of hydraulic cab mount was measured experimentally during smooth road driving at medium to high speeds.

The role of acoustic cavity modes in vehicle NVH (noise, vibration and harshness) development is well established in the automotive industry today. Prior knowledge of these modes can help prevent potential issues later in the development cycle, as well as aid in root cause analysis of vibro-acoustic issues. OEMs utilize them as part of their overall modal alignment strategy and cascade them to major system and sub-system suppliers for robust NVH designs. Today, acoustic cavity modes can be obtained rather easily using CAE (computer aided engineering) methods early in the development cycle. However, unlike acoustic modal testing, the CAE normal mode solution cannot scale the relative amplitudes of the modes. The sheer number of acoustic modal frequencies to be avoided can be a serious deterrent during the early design phase. This paper proposes an alternate approach for acoustic modal analyses using CAE to scale the relative amplitudes of cavity modes.

In recent years, Continuously Variable Transmissions (CVTs) have made significant inroads into passenger cars because of advantages over traditional Automatic Transmissions (ATs) such as improved efficiency, reduced weight and smoother operation. However, from an acceleration sound quality perspective, drivers generally seem to prefer the AT sound over the CVT sound, especially in sub-compact/compact vehicle segment with small displacement engines and cost-conscious sound packaging. Vehicles equipped with ATs maintain a linear relationship between vehicle speed and engine RPM during wide-open throttle (WOT) acceleration that is dictated by fixed gear ratios. Vehicles with CVTs typically rise rapidly to a high engine RPM (near peak engine torque) and then dwell at a constant engine RPM as the vehicle speed continues to increase by varying CVT pulley ratios.

In a traditional NVH development process, the realization of the targeted vehicle acceleration sound quality can be a highly laborious and costly process involving the creation and evaluation of multiple iterations of prototype parts. Consequently, development engineers are limited by long prototype part fabrication times while key product decision makers have to often accept the “in-process” sound quality due to aggressive program timing milestones and escalating program costs. The NVH simulator provides an alternative approach that is potentially more efficient in terms of reducing program timing, reducing development and prototype costs and improving the end-product sound quality. This paper presents the case of a V6 vehicle under development whose acceleration sound quality needed improvement. The NVH simulator was used to determine the key contributors that lead to the sound quality of the targeted vehicle.

Advancements in the area of noise and vibration control have succeeded in quieting the vehicle to the point that previously obscure squeak and rattles must now be addressed. One possible way to decrease the squeak levels is by judicious selection of the material friction pairs. The squeak levels produced by a given material friction pair are a function of a number of test conditions like interference, temperature, humidity and excitation frequency. This paper experimentally studies the dependence of squeak levels on these factors. Understanding the relationship between squeak and test conditions will guide the selection of materials and help us to carefully select the test conditions for squeak evaluations. It will also result in cost reductions to otherwise numerous and expensive squeak parameter testing.

Modern trends in noise control engineering have subjected the automobile to the “drained swamp” syndrome. Squeaks and rattles (S&R) have surfaced as major concerns. Customers increasingly perceive S&R as direct indicators of vehicle build quality and durability. The high profile nature of S&R has led manufacturers to formulate numerous specifications for assemblies and components. Even so, a large majority of buzz, squeak and rattle (BSR) issues are identified very late in the production cycle, some often after the vehicle is launched. Traditionally, the “find-and-fix” approach is widely adopted, leading to extensive BSR warranty bills. The “design-right-the-first-time” approach must replace the “find-and-fix” approach. Due to the vast breadth and depth of S&R issues, a comprehensive summary of the present state of the art is essential. This paper includes a literature survey of the current state of the art of S&R, and discusses the methods available to further advance it.

Recent advances in the field of vehicle noise control have subjected the automobile to the “drained swamp syndrome”. Quieter engines, powertrains and bodies, combined with passive sound treatments for the interior have unearthed the stumps; radio antenna wind noise is one of them. This has prompted various innovative designs and redesigns for radio antennas that have been employed by major manufacturers in recent vehicles. This paper aims to determine the optimal antenna design through experimental testing both on the road and in the laboratory.