Predicting Traffic Noise Reduction Material Effectiveness

 Pablo Giraldo-Clavijo
Pablo Giraldo-Clavijo

by Lexi Olszewski, Master of Arts in Professional Writing student

Civil engineering graduate student Pablo Giraldo-Clavijo conducted a research project that focused on investigating the effectiveness of styrofoam (a new type of lightweight materials) traffic noise walls as compared to conventional metal or concrete noise materials.

According to U.S. Department of Transportation Federal Highway Administration, noise barriers do not completely block all noise; they only reduce overall levels of sound. Effective noise barriers typically reduce noise levels by 5 to 10 decibels (dB), cutting the loudness of traffic by as much as one half. Giraldo-Clavijo’s final thesis research project could lead to a better understanding of how to select the best noise reduction material.

Assigned to the Georgia Department of Transportation's (GDOT) Northwest Express Corridor Project, Giraldo-Clavijo examined the performance of these barriers used on Interstates 75 and 575 in Cobb and Cherokee counties with the goal of understanding the actual levels of insertion loss, or the reduction of noise, that these barriers achieve.

While traveling to the various locations, Giraldo-Clavijo saw the perfect opportunity to collect noise decibel samples. “In order to measure the variance in noise generation from vehicles traveling along the interstates, samples were gathered using a Riser Pro Mini Sound Level Meter, placed both in front of and behind the barriers,” Giraldo-Clavijo explained.

Once field samples were collected, Giraldo-Clavijo performed a statistical analysis using a program called R Software. This program provides a wide variety of statistical and graphical techniques to analyze the data and support his research. Similar research has been conducted using statistical analysis software. In a recent article featured in the International Journal of Mechanics, Traffic Noise predictive Models are often used in order to predict and/or monitor the impact of the road traffic noise on the environment.

The results of Giraldo-Clavijo’s research demonstrated the effectiveness of the three noise panel materials. According to the GDOT Noise Abatement Policy, before a barrier can be considered feasible, it must reduce noise levels by five A-weighted decibels, or dB(A) — an expression of the relative loudness of sounds in the air as perceived by the human ear.

Giraldo-Clavijo found that 93 percent of the field samples were equal to or greater than five dB(A), proving that the new barriers on I-75 and I-575 significantly reduce the noise produced by cars and other vehicles. The results of his research and analyses demonstrate a clear benefit to the construction of noise barriers on interstates while serving as validation of the GDOT’s expenditure of millions of dollars to use sound barriers.

“Before starting this project, I was convinced the noise barriers were worthless and a waste of tax dollars. However, I now happily admit that I was wrong,” Giraldo-Clavijo said.

While working on the project, Giraldo-Clavijo encountered several educational opportunities, learning about the materials approved for the barriers, the geography of the locations, and the ability to combine two materials together to optimize constructability — all skills needed as he continues into the workforce.

Not only is his graduate degree preparing him for the real world, but it is also preparing him for relevant projects in civil engineering. “The research has educated me in the steps needed to execute high-profile assignments in my professional career,” Giraldo-Clavijo added.

Where others may only perceive options A through C, and few may conjure up options E through F, Giraldo-Clavijo envisions becoming the only extraordinary individual who achieves option X. “Achieving option X wouldn’t have been possible without first completing the seemingly insignificant task of writing a literature review,” Giraldo-Clavijo confessed.

As a result of the knowledge acquired during his research project, Giraldo-Clavijo has plans to continue working with his current employer to gain more experience, with the ultimate goal of advancing into higher-level positions within the company.

Lexi OlszewskiLexi Olszewski is a MAPW student with a concentration in applied writing. She enjoys working with new authors as a developmental editor for fiction. Her capstone research is focused on the rhetoric of video games and the role of professional writers in that industry. She is also a small business owner and loves spending time with her horses.