LONG BEACH, Calif. – Noise barrier walls line highways where traffic passes close to neighborhoods, parks, and schools. They are designed to reduce roadway noise that affects nearby homes and public spaces. Before a wall is constructed, engineers use a noise model to predict how much traffic noise will be reduced and whether a barrier will be effective.
The Traffic Noise Model (TNM) is the Federal Highway Administration (FHWA) tool used for this purpose. TNM is a computer-based system that estimates roadway noise based on traffic and roadway conditions and predicts sound levels at locations where people are exposed, such as building exteriors and outdoor activity areas.
DRMP Transportation Noise Group Leader Robyn Hartz, INCE, and DRMP Noise Analyst Jessica Lozada, INCE, will present “Validation in TNM3.2” at the INCE USA 2026 NOISE-CON on July 11 at 9:40 a.m. at the Westin Long Beach in California.
“Noise is always a hot topic issue for communities,” Lozada said. “As population growth increases, and with that increased traffic, it is important to be able to accurately measure and predict traffic noise levels.”
TNM 3.2 is a newer version of the model used for these predictions compared to the current FHWA-approved TNM 2.5. It is being evaluated to determine how closely its results match field measurements used in environmental review and project development. Validation is the process of comparing modeled noise levels to real-world measurements. A model is generally considered valid when predicted sound levels are within about 3 dB(A) of measured results.
The session will compare validation results between TNM 3.2 and TNM 2.5 and will examine cases where TNM 3.2 can under-predict measured noise levels. Hartz and Lozada will also discuss how those differences may affect validation practice and whether practitioners may need to adjust how they apply the model in noise barrier analysis.
“Our Noise team always strives to be efficient and innovative in our practices,” Hartz said. “We have teamed with DRMP’s Geographic Information Systems (GIS) team to streamline our noise modeling procedures and support more consistent TNM analysis. With the development of TNM 3.2 and continued validation work, we will always find ways to enhance our services and improve how we evaluate and apply model results.”
About DRMP
Since 1977, DRMP has earned a reputation as a trusted multidisciplinary engineering firm that approaches challenges differently. What began as a small Florida-based firm has grown into a Southeastern powerhouse with over 700 employees across 23 offices. We partner with clients to deliver smart, sustainable infrastructure that helps communities thrive.
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