Cerami has been retained in the past to identify and mitigate traffic noise impacts. Noise levels due to traffic flow patterns from new or expanded facilities are projected using Traffic Noise Modeling (TNM) software, in which future build conditions can be simulated. Traffic noise is comprised of several factors including traffic volumes, traffic speeds, vehicle mix, and pavement type/conditions.
In general, as traffic volumes and/or speeds increase, noise levels increase. At speeds less than 50mph, the vehicle engine and exhaust noise are dominant, while at speeds greater than 50mph, the noise from the interaction of the tires on the pavement is dominant. The vehicle mix can also affect the noise levels such that adding a greater percentage of medium/heavy duty trucks to a roadway will increase noise levels. In addition, the elevation of the noise source varies depending on the vehicle type as follows: automobiles emit noise at the elevation of the roadway (tire-roadway interaction); medium duty trucks emit noise approximately 2ft. above the roadway (combination of tire-roadway interaction and engine noise), and; heavy duty trucks emit noise approximately 8ft. above the roadway (combination of tire-roadway interaction, engine noise, and exhaust stack noise).
After conducting surveys to measure the existing noise levels, we then import this data into the program along with other data such as concurrent traffic counts. This analysis, augmented by our experience and knowledge, provides us with the ability to make recommendations both for noise mitigation, as well as assist in the planning of new roadways and developments.