Search Results

This paper looks at the changes in the vehicle passby measurement techniques over the past decades and provides some insight to the problems faced in developing the technology as well as the product improvements. While all worked diligently to reach a product level, the methods were as varied as the participants. While the us epa started the charge to quieter vehicles the lack of public interest has decreased the us activity to minimal local enforcement. Few products are a major annoyance and little public concern will minimize future programs. World interest is significantly different and the interest of the governments to protect their population from noise polution is very high. This paper will also consider some of the differences that exist in the areas and the impact on noise annoyance.

A Society of Automotive Engineers (SAE) Cooperative Research Project has established good correlation between pass-by noise data measured on U.S. test tracks conforming to SAE Sealed (sealed asphalt) and International Standards Organization (ISO) surface specifications. Although the ISO surface has a very specific track composition, it does not reduce the variability of the measurements over an SAE Sealed surface. This paper summarizes the project results and determines that the SAE Sealed surface generally produces slightly louder noise levels than a comparable ISO surface when used for pass-by testing; however, the SAE Sealed surface does not represent a consistent upper boundary for the ISO test data. The data supports the use of either track surface for pass-by procedures and suggests that road texture can influence the tire component of vehicle noise.

The object of the work reported here was to relate the acoustic intensity level measured near the contact patch of a driven tire on a passenger vehicle with the passby noise levels measured at a sideline microphone during coast and cruise conditions. Based on those measurements it was then possible to estimate the tire noise contribution to the passby level measured when the vehicle under test was accelerating. As part of this testing program, data was collected using five vehicles at fourteen passby sites in the United States: in excess of 800 data sets were obtained.

The development of systems and components for control of exterior noise has traditionally been done through an iterative process of on road testing. Frequently, road testing of vehicle modifications are delayed due to ambient environmental changes that prevent testing. Vehicle dynamometers used for powertrain development often had limited space preventing far field measurements. Recently, several European vehicle manufacturers constructed facilities that provided adequate space for simulation of the road test. This paper describes the first implementation of that technology in the U.S.. The facility is typical of those used world wide, but it is important to recognize some of the challenges to effective utilization of the technique to correlate this measurement to on road certification.

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.

Tests were conducted with a range of six light vehicles, provided by the auto industry, using a measurement system consisting of a semi-circular array of sound-intensity probes rotated around the test vehicle on a dynamometer roll. Measurements with this system showed good agreement with a standard reference source. The results with the six vehicles indicated that it is possible to develop an indoor sound-power test, as a standard of motor vehicle noise, that would be an alternative or replacement for the existing outdoor passby tests. Such an indoor test avoids the cost of delays due to bad weather, and is more convenient for noise tests of vehicles under development in indoor work areas, The results also indicate that the peaks in the narrowband sound-power spectra occur at frequencies of the orders of excitation of the various components of the power train.