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Vehicle Sound Measurement-20 Years of Testing

Ford Motor Co.-Thomas M. Howell
General Motors Corp.-Richard F. Schumacher
Published 1985-05-15 by SAE International in United States
Various SAE vehicle noise test subcommittees have been involved in numerous programs to improve and expand the applicability of procedures for increasing exterior noise levels and their relationship to the ever changing product lines. Parallel to this work, governmental and trade associations have also sought changes to better reflect the true measure of noise impact on the community. The evolution of testing has resulted in a continuing improvement in the quality of the test data. Benefits from the combined test programs have resulted in a significant improvement in the understanding of the test variability, statistical reliability, and applicability of these procedures. This paper will provide a compendium of the modifications that have evolved into the noise measurement procedures and practices in use today. The major emphasis will focus on passenger cars and light trucks. However, it will also include reference to the environmental, site and instrumentation factors that influence any vehicle testing.
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Engine Structure Analysis For Low Noise-The Options

Ricardo Consulting Engineers plc-M. D. Croker
Published 1985-05-15 by SAE International in United States
Within the limitations of the combustion process the engine structure remains the key to reducing radiated noise levels. This paper reviews the various techniques available for engine structure analysis in the context of the ever increasing computational power available to the design engineer.
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Development of an FM Multiplexed Telemetry System for Obtaining Dynamic Data from Operating Tank Track

Battelle-Columbus Laboratories-Charles W. Rodman, Howard C. Meacham
Published 1985-05-15 by SAE International in United States
A system using FM multiplexed radio telemetry was developed and built to provide a data link between operating tank track and the tank hull. Field tests of the system showed that attention to details of the design of the antenna and battery system were successful in avoiding analytical problems.The field test also demonstrated that the data obtained with the link correlated well with the results of computer modelling.
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New Acoustic Test Facilities of BMW

BMW AG-Rudolf Eilker, Norbert Herzum, Wolfgang Keiner, Albert Ulrich
Published 1985-05-15 by SAE International in United States
BMW has introduced new test stands for noise measurements on passenger cars and motorcycles.Information is given on room conditions, machinery equipment, sound levels, frequency ranges and types of measurement.The semi-anechoic room is designed for measuring the sound distribution emitted by a single vehicle. Road influence is simulated by a reflecting floor and a roller-dynamometer.The free field sound distribution in terms of distance and direction is measured in the anechoic room. This room has high-precision installations for sound source identification and noise mapping.The reverberation room serves to measure sound power emitted by the test object. Its second purpose is to subject the bodywork to a high-power external sound source and to measure the sound-deadening effect of the passenger compartment.In conclusion, the presentation provides reports on the initial experience with these test facilities.
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A Study of Vehicle Interior Noise Using Statistical Energy Analysis

Cambridge Collaborative, Inc., Cambridge, MA-Richard G. DeJong
Published 1985-05-15 by SAE International in United States
The noise and vibration of an automotive vehicle is studied using Statistical Energy Analysis (SEA). Three sources of interior noise - the engine, tires, and air flow - have been measured and used as inputs to the SEA model. The flow of acoustic energy through various structural components is calculated in order to determine the dominant paths of noise transmission to the passenger compartment. The predicted interior noise levels are compared to those measured under different operating conditions. The SEA model also evaluates the expected variation of the interior noise as the result of changes in the design configuration of the vehicle.
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Characteristics of Exciting Forces and Structural Response of Turbocharged Diesel Engines

Southampton University-T. Priede, J. M. Baker, E. C. Grover, R. Ghazy
Published 1985-05-15 by SAE International in United States
The paper quantifies the forces applied to the main bearings of three six-cylinder turbocharged diesel engines and reviews their exciting properties in both time and frequency domains. The engine structure response at the bearing supports and the outer engine surfaces are correlated. It is shown that the engine structure response is a transient phenomenon and is a maximum in the vicinity of the applied force. By representing the engine response in terms of displacement it is possible to recognise the applied force time history and thus the identification of the specific parts of the engine structure primarily excited by moments and by direct force. The displacement technique for quantifying engine response provides detailed information of the distortion of the running engine enabling the prediction of mechanical inputs which can control the turbocharged engine noise. This is essential for quantifying input data for theoretical models and establishing structure changes to control engine radiated noise.
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Understanding Hydraulic Mounts for improved Vehicle Noise, Vibration and Ride Qualities

Lord Corp. Erie, PA-Wallace C. Flower
Published 1985-05-15 by SAE International in United States
It is now apparent that properly applied hydraulic mounts can significantly alter the perceived performance of current production automobiles. Benefits such as reduced interior noise and vibration levels, and improved ride, especially on moderate to rough roads, are now attainable. Such improvements require the careful design and application of hydraulic powertrain mounts, utilizing a variety of hydraulic design options, some or all of which may be appropriate to the specific vehicle application under consideration.
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Interactive Computer Simulation of Drivetrain Dynamics

Ford Motor Co.-M. C. Tsangarides, W. E. Tobler, C. R. Heermann
Published 1985-05-15 by SAE International in United States
Computer simulations of vehicle dynamics can be a useful investigative tool in drive-ability and NVH studies. As the present work demonstrates, oscillations of the drive-train under steady-state and transient conditions are amenable to mathematical analysis, especially in the torsional mode. Simulations of such a system with a lock-up torque converter are shown with emphasis on tip-in response, transmissibility of engine firing pulsations and self-excited oscillations. In particular, the method of interactive simulation is shown to be an effective design-aid tool in the investigation of drivetrain vibrations.
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Using Modal Analysis, Modeling and Analytical Modifications to Aid in the Development of Automotive Structures

Structural/Kinematics-Dean Hauersperger
Published 1985-05-15 by SAE International in United States
Modal Analysis has been advanced to the point where it can enable the user to, with a high degree of confidence, select an optimum set of modifications that solve a problem analytically. The means to that end are not only very important, but also very critical.There are three phases to an analysis of this type. First, the test parameters must be determined. Second, the measurements must be taken. This phase is only worthwhile if the first step is done correctly. The third step is the creation of the modal model (parameter estimation). Again, this phase should only be performed if the first two were done correctly.A usable/accurate modal model is useless, if. not dangerous, if the person exercising it does not understand completely what it means and what the results mean.This paper addresses the concerns, techniques, requirements, and assumptions often forgotten when using modal analysis to generate a model of a structure.
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A New Ride Quality Meter

NASA Langley Research Center-Jack D. Leatherwood
Wyle Laboratories-John J. Wood
Published 1985-05-15 by SAE International in United States
An overview of the development of a NASA ride comfort model is presented. A new instrument is described, the Ride Quality Meter, which incorporates the NASA-developed model to characterize ride comfort based upon measurement of vehicle interior noise and vibration. The meter is a portable unit which provides real-time estimates of passenger ride comfort during actual vehicle operations. It provides the first known capability to directly sum the effects of noise and vibration into a single objective comfort index. The meter has been shown to be applicable to passenger cars, trucks, buses, trains, aircraft, and a wide variety of special purpose transportation systems. Data is summarized demonstrating application to automobiles and helicopters. The meter has been shown to perform as a reliable and accurate passenger jury.
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