New Hampshire Department of Transportation Statewide Noise Barrier Study

Abstract

This paper presents the results of a statewide noise barrier study for the New Hampshire Department of Transportation (NHDOT). The feasibility and reasonableness of noise barriers throughout the state has been evaluated according to NHDOT acoustical and cost-effectiveness criteria. The study has provided the DOT with an estimate of the potential noise barrier material costs associated with a newly implemented Type II noise barrier program. The study also has identified municipalities that the DOT can coordinate with for enacting noise-compatible planning regulations. The paper describes the methodology used to develop the screening-level noise barrier evaluation. Highway noise levels throughout the state and the distances from the highway where noise levels exceed the noise abatement criteria were determined. A method to predict the noise reduction of barriers (insertion loss) based on a simple geometrical relationship of receptors and potential noise barriers was established and has been shown to correlate well to detailed traffic noise models using actual roadway and terrain geometry. The simplified prediction method was used to evaluate over 300 miles of highway, 300 candidate noise barrier study areas, and over 30,000 receptors. This screening-level modeling approach is critical to the practicality of using the Traffic Noise Model across the entire state given the significant number of receptors and noise barrier study areas. The results of the study including information about all 30,000 receptors and 300 noise barrier study areas were collected in Google Earth™ data files for easy access when the DOT responds to noise complaints from the public.

Overview of Noise Control Techniques and Methods

“…The relation between the IL and the shielding angle from the receiver does not depend on the distance from the receiver to the barrier, as stated by Ross et al [27] after analyzing a set of 300 sites with barriers from 90 to 1100 m in length. When studying the behavior of barriers of the same length and different heights, the shielding angle should be at least 165°to reach a good IL value.…”