DCC conducted noise and vibration studies in support of the Federal Surface Transportation Board (STB) EIS for the Burlington Northern Santa Fe Bayport Loop Project in Houston, Texas. This project involved many different types of noise and vibration studies including:
Ambient noise measurements
Baseline and future train noise contours
Construction noise and vibration analysis
Ambient Noise Measurements
Because this project would consist of construction of a new rail line, ambient noise measurements were required in order to assess the potential increase of noise due to the project. DCC measured ambient noise in the project area at several different noise sensitive locations for 24 hours. STB employs a noise metric called 'Day-Night Average Noise Level' (DNL) which is essentially a 24-hour average with a ten decibel penalty for nighttime noises to account for peoples' increased sensitivity to noise at night. The ambient noise measurements indicated that the project would cause increases in noise level less than 3 decibels due to the high existing ambient noise levels. High ambient noise levels in the study area were caused by military aircraft activity at Ellington field and other various noise sources.
Baseline and Future Train Noise Contours
DCC developed noise contours for baseline existing conditions and future conditions. This analysis was conducted in order to count the number of sensitive receptors (e.g., homes) within the 65 DNL contours and determine the increased number of receptors affected by the project. Figure 1 shows an example noise contour map of a portion of the rail network that was studied. Figures 2 through 6 show closer views of the contours in particular areas. These contours were generated using three-dimensional acoustic modeling software. This type of approach is necessary to account for the effects of building shielding. In areas where buildings are close to the tracks and to each other, acoustical shielding provided by buildings can block the sound that otherwise might affect homes further from the tracks.
The teardrop shaped noise contours indicate the presence of locomotive horn sounding. Horn sounding is required at at-grade highway-rail grade crossings to alert oncoming motorists of trains. At such grade crossings, the 65 DNL noise contour can extend several hundred feet from the tracks depending upon a variety of factors including number of trains per day.
Figure 1. Portion of Rail Network-65 DNL Noise Contours
Figure 2. Example Noise Contour
Figure 3. Example Noise Contour
Figure 4. Example Noise Contour
Figure 5. Example Noise Contour
Figure 6. Example Noise Contour