1200 feet
200 feet
About 12 feet for the single French Horn, although the double horn and some different models could have slight variations.
200 feet
50 feet
The roar can be heard for up to two miles away.
It has to be at least eighty feet away Not it has to be fifteen
25 feet
3 feet
200 ft
http://wiki.answers.com/Q/A_horn_must_be_loud_enough_to_hear_within_how_many_feet"
3,000 feet