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The character and level of noise in a vehicle has changed significantly from the 1970s to today. In the 1970s the challenge was to permit communication from the front seat to the rear at highway speeds. In the last decade, the challenge has grown to provide a vehicle that provides the right "type" of sound while isolating the occupants from disturbing exterior noise. This may involve adding engine noise simulation and sculpting the interior sound to meet customer expectations. More recently, the challenge has been to modify noise controls for extreme light weighting exercises and electric vehicles. In addition, electric vehicles present a different sound environment and the challenge of determining what an EV should sound like. This paper will attempt to discuss these challenges and talk about the future of vehicle interior noise.

As other vehicle systems have become more refined, more attention must be placed on brake NVH issues because they can cause a negative customer experience. From the laboratory to the road, the use of technology as well as further study by engineers is helping to lessen noise, judder, and vibration in cars. This book provides readers with a fundamental understanding of current practices for measuring and testing brake NVH. From coverage of basic definitions and concepts to in-depth analysis of on-road testing procedures, it will serve as a comprehensive reference guide for brake test technicians, test engineers, lab managers, and others who work on making brakes quieter, smoother, more refined, and more reliable. Readers will learn how to test for brake noise, what tools to use, and which recent standards and practices have led to the successful measurement of brake noise and vibration.

This paper presents the work of the SAE Brake NVH Standards Committee in developing a draft Low-Frequency Brake Noise Test Procedure. The goal of the procedure is to be able to accurately measure noise issues in the frequency range below 900 Hz using a conventional shaft brake noise dynamometer. The tests conducted while evaluating alternative test protocols will be discussed and examined in detail. The unique issues encountered in developing a suitable test procedure for low-frequency noise will be discussed, and the results of tests using both shaft brake dynamometers and chassis dynamometers will be described. The current draft procedure incorporating the knowledge gained from this development effort will be described in detail and conclusions as to its applicability will also be presented

The development and validation of a brake pad insulator damping measurement procedure by the SAE Brake NVH Standards Committee is described in this paper. The details of the test procedure, test set-up and recommendations for proper test practices are described. The description provides an excellent foundation for evaluating the damping properties of a shim over a range of frequencies and temperatures. To document the repeatability of the measurement process, a Gage R&R study was conducted. The results show that a high level of repeatability is achieved over a range of temperatures and damping properties. An example application is described to illustrate the usage of the procedure. This example provides an excellent illustration of how this procedure can be used to select the best shim for a specific application. Conclusions as to the applicability of this procedure and its value to brake noise control are provided in the final section.

As part of the development of a New SAE Recommended Practice for Brake Natural Frequency and Damping Measurements, the US Working Group on Brake NVH conducted a series of Round Robin tests and developed detailed recommendations for such measurements. The results of these tests are summarized in this paper. Initial results showed that there were difficulties with the identification of the types of modes being measured. However, when the results were carefully categorized, the measured natural frequencies agreed quite well. The measured damping coefficients showed much larger variations. In some instances, differences of more than 200% were found between testers. The steps taken to improve the consistency of results and subsequent Round Robin tests are described.

A thorough examination of the use of inertia simulation to provide dynamometers capable of accurately representing vehicle performance is presented. A description of a dynamometer system for brake testing using inertia simulation is provided. The models used to properly represent inertia losses, and both the programs and the results from experimental verification are described. The limitations due to motor power and existing fixed inertia in the system are described. Vehicle and dynamometer characteristics discussed include linear inertia, tire rolling resistance, bearing losses, windage, inclines, and motor field effects. Inertia simulation is shown to accurately model both steady state and transient vehicle performance.

There is a growing emphasis on the transfer of testing from the proving ground to the laboratory. The rapid evolution of test technology has been a key to making such transfers possible. This paper presents a description of the methods, including the critical data acquisition and the control parameter generation processes, developed to efficiently perform the move from the proving ground to the laboratory. Software tools are described that permit the user to collect vehicle control and response inputs on the road and convert these to test system control parameters. The process of collecting data is shown to be straight forward with a great deal of flexibility in terms of the type and number of channels to be collected. The conversion of these data to control parameters is described with examples. Parameters included in these studies include speeds, loads, vehicle inclination, accelerations, temperatures, torques, pedal positions, pedal force, time and distance.