The Siren Board

Hi! wondering if anyone out there can help me out with a question regarding train horns? Someone had suggested to me that train horns provide "unidirectional noise" rather than "omni directional". As far as I can see - only ultrasound creates unidirectional noise. Trying to establish safe distance guidelines (to protect hearing) from a train horn used in a unique application - horn is stationary - not moving (as it would be on a moving train). Trying to confirm that standard noise calculations apply with train horns. Thxs.

straight from the Federal Railroad Administration:

The maximum volume level for the train horn is 110 decibels which is a new requirement. The minimum sound level remains 96 decibels.

https://www.fra.dot.gov/Page/P0889

Like sirens, they're rated @ 100ft

If memory serves me right, the AirChime K5LA, the most common horn in north america is rated 115db @ 100 ft.

https://www.youtube.com/watch?v=UUNnC-9XMnI

at 10 ft they can reach 120+db. Good ruse of thumb, if you're doing a static test of a locomotive horn (stationary test), wear muff style hearing protection, even if you stand behind the horn. I've had my ears "cleaned out" by my Nathan M3 inside a pick up cab with all the windows open, with the horn mounted on the roof, just before a run by. If you're sitting at a crossing and worried about the horn of a passing locomotive, you'll be fine without any hearing protection for the brief time it takes for it to pass by.

Most horns are about 105 db at a hundred feet, but it depends on the horn and where I hear it. I've heard some air horns topping 115 up close, and I've heard some at about 95 at the same range, and it depends on the engine too.