Air horns -- more efficient horizontal or pointing down?

[Daniel]

Most American air horn installations have the horns placed perfectly horizontal, while Europeans (mainly the Scandinavians, who love these things) usually angle the horns downward. Obviously a downward angle would help prevent unwanted water entry, but one would think that the effective coverage area would be somewhat lessened. Also, most horizontal American horns I've seen date from the 40's and 50's and have needed little or no maintenance to the horns themselves. Any ideas for advantages either way?

[Jim_Ferer]

The only conceivable advantage to pointing horns down is echo off the pavement, and I can't figure out how that would be better than horizontal. One thing, pointing a horn at the pavement would be more dispersion.

[Robert Gift]

I would aim the horn horizontally, at the intended victim.

Downward disperses sound energy in other directions, needlessly bothering those who don't need to hear it.

This is why I like the Q2 flush mounted.
More sound to the front and sides and less going behind where bothersome and unneeded.