M.S. Thesis Presentation by David Sangchaul Moon
Tuesday, May 26, 1998

(Dr. Ken Cunefare, advisor)

"Quantification of Airborne and Structureborne Acoustics and Vibrational Signature of an Automotive AIR Pump Using an Anechoic Chamber"

Abstract

The analysis of automotive components for acoustical properties has become an area of increasing interest due to customer demands for lower Noise, Vibration, and Harshness (NVH) levels. Automobile makers have placed a high priority on reducing NVH levels both in new product design and current vehicle development.

The air injection reaction (AIR) pump is an emissions-related device that pumps ambient air directly into the exhaust manifold of an internal combustion engine to aid the catalysts in reducing emissions during engine start up. A Borg-Warner AIR pump is used by General Motors in the new 1999 C/K full size pickup truck series. Product development emphasis currently lies in analyzing airborne and structureborne acoustical performance and vibration, with the goal of reducing noise radiation from the pump and its mounting components.

This thesis focuses on analyzing the airborne and structureborne acoustical and vibrational properties of the air pump with its related mounting hardware. An anechoic chamber is used to simulate a free field environment, with HP VXI hardware and LMS software facilitating data acquisition. Free field measurements of source sound directivity, sound power level, and spectral content are taken. In addition, accelerometer-measured transmissibility is analyzed to compare two (2) types of rubber mounting isolators. This data could be used to implement modifications to reduce the acoustic radiation of the AIR pump assembly.