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Driving comfort and automotive product quality are strongly associated with the vibration that is transmitted to the occupants of a vehicle at the points of contact to the human body, including the seat, steering wheel, and pedals. Of these three contact locations, the seats have the most general importance, as all occupants of a vehicle experience seat vibration. Particularly relevant to driving comfort is the way in which vehicle occupants perceive seat vibration, which may be different than expected considering sensor measured vibration levels. Much of the interest in seat vibration has been focused on internal combustion engine powertrain vibration, especially idle vibration. However, electrification of vehicles changes the focus from low frequency idle vibration to higher frequency vibration sources.

Due to the nearly silent operation of an electric motor, it is difficult for pedestrians to detect an approaching electric vehicle. To address this safety concern, the National Highway Traffic Safety Administration issued the Federal Motor Vehicle Safety Standard (FMVSS) No. 141, “Minimum Sound Requirements for Hybrid and Electric Vehicles”. This FMVSS 141 standard requires the measurement of electric vehicle noise according to certain test protocols; however, performing these tests can be difficult since inconsistent results can occur in the presence of transient background noise. Methods to isolate background noise during static sound measurements have already been established, though these methods are not directly applicable to a pass-by noise test where neither the background noise nor the vehicle itself as it travels past the microphone produce stationary sound signals.

In a previous paper [1], a method was introduced to predict the sound transmission loss (STL) performance of multi-layer panel constructions using a measurement-based transfer matrix method. The technique is unique because the characterization of the poro-elastic material is strictly measurement based and does not require modeling the material. In this paper, it is demonstrated how the technique is used to optimize the STL of lightweight, multi-layer panel constructions. Measured properties of several decoupler materials (shoddy and foam) are combined with sheet metal and barrier layers to find optimal combinations. The material properties are measured with the impedance tube per ASTM E2611 [2].

A large body of knowledge exists regarding the effects of vibration on human beings; however, the emphasis is generally on the damaging effects of vibration. Very little information has been published regarding the effect of vibration on perceived consumer product quality. The perceived loudness of a product is quantified using the Fletcher-Munson equal loudness curves, but the equivalent curves for perceived vibration amplitude as a function of amplitude and frequency are not readily available. This “vibration quality” information would be valuable in the design and evaluation of many consumer products, including automobiles. Vibration information is used in the automobile design process where targets for steering wheel, seat track, and pedal vibration are common. For this purpose, the vibration information is considered proprietary and is generally applicable to a narrow frequency range. In this investigation, work paralleling the original Fletcher-Munson study is presented.

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.

Using a tube apparatus, sound transmission loss measurements can be performed per ASTM E2611-09. Usually the intent of these measurements is to determine the sound transmission of an infinite sheet of material (i.e. the one-dimensional (1D) absorption) of a specific thickness. These results are used in simple room acoustics models and in finite element models. The tube measures the sound transmission loss of a round sample constrained within a tube which, due to edge constraint, can be quite different from the 1D transmission loss. This same issue is seen when measuring the sound absorption of material samples. The edge constraint effect is examined for automotive materials (sheet metal and vinyl barrier material) measured in a tube configured to measure transmission loss, and alternate mounting methods are investigated. The results are compared to theoretical results.

A project is described where spherical beam-forming was used to perform real time evaluation and development of an automotive dash silencer assembly. By eliminating the iterative laboratory sound transmission loss testing, significant advantages were achieved in part development. These advantages include a reduction in development cost and time, reduced part cost, and lower part mass. Reducing the time to develop lighter and less expensive sound package parts was the most obvious benefit of the project, but the process also: 1) eliminated the time and cost to procure competitive parts; 2) allowed the evaluation of the parts in-vehicle rather than on a laboratory buck; and 3) reduced the time required with the development vehicle.

This paper describes the application of the modal compliance method to a complex structure such as a vehicle body in white, and the extension of the method from normal modes to the complex modes of a complete vehicle. In addition to the usual bending and torsion calculations, the paper also describes the application of the method to less usual tests such as second torsion, match-boxing and breathing. We also show how the method can be used to investigate the distribution of compliance throughout the structure.

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.

During the development of a new vehicle, the vehicle is usually tested to determine both its static torsional and bending stiffness, and its dynamic torsional and bending modes. This paper discusses a method for determining both static and dynamic properties from the modal analysis test. Such a connection between static stiffness and dynamic modes would be useful for three reasons: (1) the relative importance of apparent bending and torsion modes could be determined by their contribution to stiffness, (2) the stiffening effect of structural modifications could be determined from experimental modal tests (the modal frequency shift is also affected by any change in mass), (3) the total static compliance could easily be split on a modal basis into compliance due to the overall structure and local compliance due to local structural deflections.