How a R.R. determine what type of horn to install on their locomotive? Do we have a standard horn for locomotives? Its by the size or tonnage?
air horns (whistles) are generally an “option” which is modified from a builder standard based upon the customer’s requirement or specification. Some railroads, such as Chessie System, actually went with the Nathan Co. and tested various musical notes and types of whistles on locomotives someplace out in Maryland or Pennsylavania, if I remember. This is how the K5LA came about, as Chessie wanted something, according to reports, that sounded more like a steam whistle, notre-wise, than the equipment then currently available.
I would have to say the ‘old tuned’ K5HL, which uses the 1, 1L, 2, 3, & 4A bells:
Norfolk Southern had that happen in Springfield, IL, at one point. Someone knicked a few horns off of the locomotives. “Best” part is, I got suspected at one point in that. Got a call from the NS Police Department, too.