How does train horn noise diminish as distance from the track increases?
The FRA has modeled how the train horn sound propagates and dissipates from its source. The FRA model states that train horn noise is reduced by 4.5 dBA whenever the distance from the train is doubled. This horn noise dissipation is caused by divergence of sound and ground interference. The FRA model also considers shielding from buildings and includes a 3 dBA reduction at the first row of buildings, located 200 feet from the track, and additional 1.5 dBA reductions for each succeeding row at 400, 600, 800 and 1,000 feet. Assuming an average of 104 dBA of horn noise at 100 feet from the train, the chart at left shows how the FRA models the dissipation of noise as distance from the grade crossing increases. This model shows that speech interference can begin to occur approximately 7,000 feet from the track when the train horn is sounding. People, outside and closer than 1,500 feet from the track, may have to shout to be heard. Outside conversations, closer than 400 feet from the track,
