Case Study: Reflective and Non-reflective Highway Barriers

K. Polcak (MD SHA)
And
R.J. Peppin (Scantek, Inc.)

TRB ADC 40 Summer Meeting, Denver, CO

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Not all highway sound barriers control noise the same way. A reflective wall blocks sound on one side but can also reflect noise back across the roadway or toward nearby receivers. An absorptive barrier is designed to reduce reflected sound by absorbing part of the sound energy rather than reflecting it back.

This case study examines reflective and absorptive highway noise barriers, based on research by K. Polcak of the Maryland State Highway Administration and R.J. Peppin of Scantek, Inc. The main takeaway is simple: a sound wall is often better than no wall, but the type of wall matters. In some settings, absorptive panels may be the better choice, while reflective barriers should be reviewed carefully before they are specified.

Key Takeaways From the Highway Barrier Study

The study points to several practical conclusions for highway noise barrier design:

• A properly designed sound wall is usually better than having no barrier at all.
• Absorptive panels can reduce reflected sound compared with hard reflective surfaces.
• Reflective barriers may create problems in some roadway settings, especially where reflected noise reaches nearby receivers.
• Small differences in absorption ratings may not always create a meaningful field difference.
• Reflective barriers should be reviewed through a site-specific noise study before they are selected.

For transportation departments, engineers, and project owners, the decision should not be based solely on wall height. The material, surface type, roadway geometry, receiver locations, and acoustic goals all affect the final result.

When This Research Applies

This case study is useful for projects where reflected transportation noise may affect nearby communities, properties, or opposite-side receivers. Common examples include:

• Highway expansion projects
• Roadway noise mitigation near residential areas
• DOT and municipal sound wall planning
• Bridge, overpass, and divided highway applications
• Replacement of older reflective noise walls
• Projects comparing absorptive and reflective barrier materials

Sound Fighter Systems manufactures absorptive noise barrier systems for transportation, utility, industrial, commercial, and energy applications. For highway projects, our team can help review whether an absorptive wall system is a practical fit for the site conditions.