Train horns

I first saw these on YouTube under Hornblasters. Some guys in Florida got some hilarious video, but the very best was when they got a cop to get up close to a headlight with his face. That guy was NOT impressed by getting blasted at point blank range by the horn.

 

They blast the cop with the horn at the end.

 

The original question was about train horns. What trucks have installed are not train horns. K5LA is a train horn and I highly doubt it is legal to be installed on a truck.
I will attach a link with a video on youtube to better clarify my point. Watch and listen and then decide for yourself what a train horn really is. Crank the volume a bit to get the idea of what a train horn sound like.

 

Why can you hear the bells like at the actual crossing on all the horn passes??? Makes it look and sound fake.