DESIGN OF CONCRETE BARRIERS FOR LIGHT RAIL SYSTEM BASED ON NOISE REDUCTION RESEARCH

If light rail ever becomes a reality in Hampton Roads, the research of an Old Dominion professor could well play a part in its success.

Oktay Baysal, associate dean of the College of Engineering and Technology and professor of aerospace engineering, began research last spring for Bayshore Concrete Products Corp. to reduce noise through the use of concrete barriers for a light rail system that will run between downtown Manhattan and New York's JFK International Airport.

The project evolved after company officials contacted Old Dominion's Technology Applications Center for assistance with their dilemma -- how to create a concrete barrier for a light rail system that fits within the environmental noise limits set by the Port Authority of New York and New Jersey. Bayshore, whose manufacturing plant is located in Cape Charles on Virginia's Eastern Shore, bid on -- and eventually won -- the contract to be the material supplier to the air-rail transit consortium that is building the light rail system.

Before it could bid, however, Bayshore needed to come up with a cost-effective concrete barrier that could also reduce the noise level from the trains, which would run primarily through densely populated areas.

According to specifications, the barriers would have to reduce the noise generated by the trains to 75 decibels or less at 50 feet away from the center of the tracks.

Noise research was not new to Baysal, who has studied the aeroacoustics of jet and aircraft noise for NASA. But concrete barriers were. The goal, he said, was to shape the top surface of the barriers to deflect the low frequency of sound produced by the trains.

Using a database of noise that these particular trains generate, Baysal and two of his doctoral students began their research, which was funded by Virginia's Center for Innovative Technology, by writing equations that model the noise. Through modeling and simulation techniques, they made the noise visible, which helped them learn more about how the sound waves were propagated, and then wrote a physical equation for wave and particle movement.

Once the team understood the noise, they were able to move on to the design of the concrete barriers themselves, which could be no more than four and a half feet high or eight inches thick, according to William Harris, project manager for Bayshore's JFK castings operations.

Using a variety of engineering techniques that included the use of calibrated microphones and studies of wheel to rail interaction, Baysal and his students came up with a design that they believed would meet the Port Authority of New York and New Jersey standards. Bayshore then constructed a prototype that the researchers tested, using loudspeakers to imitate the sound created by the trains.

The test proved successful. Based on the test parameters, Baysal said their design should be able to reduce the maximum allowable decibels by about 15. Construction of the light rail system, which will include 7,500 of Bayshore's concrete barriers, has already begun and is expected to be completed by 2002.