Noise Analysis & Barrier Design

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Transportation systems cause some of the most invasive sources of noise in the environment. Highway traffic noise is a leading source of noise throughout urban and rural environments. The National Environmental Policy Act (NEPA) of 1969 has broad authority and responsibility to Federal agencies for evaluating and mitigating adverse environmental effects, including traffic and construction noise. The Federal Highway Administration (FHWA) has developed and implemented several regulations for the analysis and mitigation of traffic noise in Federal-aid highway projects in response to the Federal-Aid Highway Act of 1970. The regulations require the following during the planning and design of a highway project:

1. Identification of highway traffic noise impacts
2. Examination of potential abatement measures
3. The incorporation of reasonable and feasible highway traffic noise abatement measure into the highway project
4. Coordination with local officials to provide helpful information on compatible land use planning and control
5. Identification and incorporation of necessary measures to abate construction noise

To perform an Analysis of Traffic Noise Impacts, the expected traffic noise impacts must be determined and analyzed. Noise impacts for projects on new alignments must be determined by field measurements. For projects on existing alignments, predict existing and design year traffic noise impacts. Highway traffic noise impacts occur when the predicted existing or future highway traffic noise levels approach or exceed the noise abatement criteria (NAC) or when predicted existing or future highway traffic noise levels substantially exceed the existing highway traffic noise level.

The most commonly used form of noise abatement are noise barriers. Noise barriers are the only form of abatement required for consideration on Federal or Federal-aid projects. Noise barriers are solid obstructions built between the highway and the noise receivers along the highway. Effective noise barriers are capable of cutting the loudness of traffic noise in half. Barriers can be in the form of earth berms, high, vertical barriers, or a combination of both.

HMB has provided Traffic Noise Impact studies on numerous transportation projects throughout the region. These studies are then used to design an effective noise barrier.