Study of tire/pavement interaction noise generation using Nearfield Acoustical Holography.
Tires are a dominate source of automobile noise. This creates noise problems along highways, difficulties in meeting regulated noise laws (both domestic and international), and noise complaints from the passengers. With an improved understanding of tire noise, it may be possible to design tires to reduce pass-by noise levels. In addition, pavement textures could be designed to reduce highway noise equal to the reduction now possible with noise barriers.
Nearfield Acoustical Holography (NAH) will be used to localize areas of radiation from tires. NAH was first developed over ten years ago at The Pennsylvania State University. By applying NAH theory, a three-dimensional acoustic image can be mathematically reconstructed from measuring the complex pressure (containing both magnitude and spatial phase information) at discrete points along a two-dimensional surface very close (i.e. "near-field") to the vibrating surface. The acoustic field is made up of two waves that are distinguished by NAH: evanescent waves which help identify acoustic sources but decay exponentially with distance, and propagating waves that contribute to the radiated noise in the farfield. Since NAH measurements are conducted in the nearfield, areas of maximum radiation may be localized with a much finer resolution than with conventional measurements.
This research is made possible through a 3-year fellowship (Eisenhower Transportation Fellowship - US DOT) and a 1.5-year research assistantship funded by The Goodyear Tire & Rubber Company. General Motors has assisted us and allowed us to use their facilities at the GM Proving Grounds in Milford, Michigan. Goodyear has provided most of the tires we evaluated. Three phases of testing have been completed (see photo of apparatus below). The image on the top of my homepage shows the active intensity at 390 Hz along the side of a tire when rolling at 35 mph. For more detail e-mail me, or see the following papers:
R. J. Ruhala and C. B. Burroughs, "Application of nearfield acoustical holography to tire/pavement interaction noise emissions," SAE 972047, Proceeding of the 1997 SAE Noise and Vibration Conference, pp. 1397-1406, May 1997.
R. J. Ruhala and C. B. Burroughs, "Separation of leading edge, trailing edge, and sidewall noise sources from rolling tires," Proceeding of NOISE-CON 98, pp. 109-114, April 1998.
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