Engineers tread toward quieter tires

Engineers have developed a new method for reducing tire noise - which is responsible for most of the noise nuisance from Interstate highways.

Purdue University in Lafayette, Ind., reports that its scientists have analyzed tire vibrations by creating a "fingerprint" that identifies which features produce the most noise.

A tire's tread contains block shapes that smack against the road surface like tiny hammers. Those tread blocks and underlying reinforcing belts vibrate and radiate

energy outward, producing sound much like the vibrating cones in stereo speakers. Different portions of the tire vibrate faster than other portions, producing more noise.

Stuart Bolton, a professor of mechanical engineering, and graduate student Yong-Joe Kim are using a mathematical model to identify which parts of a tire produce the most noise. The vibrations are characterized on a graph, a visual representation that's like a fingerprint of each tire's vibration pattern.

The engineers measure various vibrational waves that travel along a tire's treadband, the outer segment of a tire that includes reinforcing belts and the tread pattern that meets the road's surface. Specific vibrations are assigned "wave numbers," used to determine the portions of the tire from which they emanate.

"We've introduced a way of experimentally looking at tire vibration in a way that identifies components that can generate the most sound," says Mr. Bolton, who wrote a research paper with Mr. Kim describing the work. The paper will be presented Aug. 27, during the 30th International Congress and Exhibition on Noise Control Engineering in The Hague.

The work is being conducted at Purdue's Institute for Safe, Quiet, and Durable Highways as part of a contract supported by the US Department of Transportation, Ford Motor Co., and several tire manufacturers.