Noise is considered unwanted sound, particularly when the sound causes annoyance. Noise comes from many sources. One of the most significant sources is from transportation, particularly traffic noise.
Highway noise comes from three sources: the engine, the exhaust and the interaction of the tires and pavement. Once typical highway speeds are reached, the predominate noise from light trucks and cars is from the tire/pavement interaction. Heavy trucks produce a high volume of noise from all three sources even at high speeds.
Mitigating transportation noise in the environment is important for the health and welfare of the surrounding community. Numerous studies have demonstrated the effect of noise on the health of those suffering under its impact. Effects ranging from hearing loss to cardiac arrest have been linked to noise. Prolonged exposure to noise in excess of 75 dBA (deciBels Adjusted) may initiate hearing loss. Noise may also negatively impact the quality of life of those who must live with it. Loss of sleep and the inability to hold conversations are frequent complaints. Helping to alleviate these negative impacts is the objective of noise abatement.