sealPurdue News

October 1999

New institute to begin research into quiet highways

WEST LAFAYETTE, Ind. -- Engineers at Purdue University have formed the first center in the nation dedicated to understanding the precise physics behind highway noise, a prerequisite for reducing the nuisance.

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"Traffic noise is a persistent long-term environmental effect of highways," says Bob Bernhard, director of the new Institute of Safe, Quiet and Durable Highways at Purdue.

The institute was dedicated today (Friday, 8/27), and research will begin in September.

The numerous buffers installed between freeways and residential neighborhoods attest to the problem, says Bernhard, a professor of mechanical engineering, who points out that building barriers to wall out the road racket can cost as much as $1 million per mile.

"Residents rarely complain about being able to see a highway, but they often complain about highway noise," he says.

It may come as a surprise, Bernhard says, that most of the acoustical pollution from cars doesn't come from engine noise but from the interface of tires and road surfaces.

Engineers suspect that several mechanisms are to blame, including:

  • Air that is trapped and compressed between a tire's tread pattern and the road surface eventually bursts from the confining spaces, causing pops and whistles.

  • The block-like shapes in the tread design smack against the road surface, like numerous tiny hammers.

  • Those tread blocks and the underlying belts vibrate and radiate energy outward, producing sound much like the vibrating cones in stereo speakers.

    Purdue engineers propose to attack the problem by studying both tires and road surfaces. The results will then be used to design tires and road surfaces that make less noise.

    "The research in this institute is really where the rubber meets the road," says Vincent Drnevich, the institute's co-director and head of the Purdue School of Civil Engineering.

    Research will include the use of lasers and sound waves to analyze noise-producing mechanisms in rotating tires. Engineers will study porous pavements that have been used in Europe to build quieter roads.

    "European researchers have hypothesized the mechanisms of noise generation and built quiet, porous road surfaces," Bernhard says. "These hypotheses haven't been proved, and that's what we are going to go after.

    "The additional challenge is to keep tires and roads safe, durable and affordable at the same time."

    The institute is a joint project of Purdue's schools of civil and mechanical engineering in collaboration with researchers from the Pennsylvania Transportation Institute at Penn State University, where researchers will make a database of sound produced by transit buses in efforts to reduce bus-related noise pollution, he says.

    Findings from laboratory research will be incorporated into civil and mechanical engineering classes at Purdue. The findings also will be transferred to the highway and tire industries through workshops and design guidelines.

    The institute is funded by a $3.6 million grant from the U.S. Department of Transportation and an equal amount from other government and private sources.

    It will expand later to include research dealing with other sources of transportation-related noise, such as truck engines, as well as issues involving highway safety and durability, Bernhard says.

    Source: Bob Bernhard, (765) 494-2141;

    Writer: Emil Venere, (765) 494-4709;

    Purdue News Service: (765) 494-2096;


    Jacob Klos, left, a Purdue graduate student in mechanical engineering, and Bob Bernhard, an engineering professor and director of the university's Institute of Safe, Quiet and Durable Highways, use a laser to study how noise is generated by a smooth tire on a textured surface. The tire, painted white to better reflect laser light, is rotated on a motor-driven roller. The laser measures vibration, and the data are relayed to a "signal analyzer" for interpretation. (Purdue News Service Photo by David Umberger)

    Color photo, electronic transmission, and Web and ftp download available. Photo ID: Bernhard.roads

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