The larger and longer an air horn is, the louder and deeper it is capable of being when sounded. Additionally, the higher the pressure used to honk the horn – the louder the overall sound will be. Because of this, the Roof Mount Horns will be very loud and very deep-sounding, but will only produce a single note. Multiple trumpets of varying lengths produce a combined tone, that some find more pleasing. Depending on the type of vehicle your horn will be installed on – always select the largest horn you can fit onto your vehicle. Direct Drive Horns will not be as loud as our air tank-driven Compact Air Horns and the Compact Air Horns cannot rival our Train Horns for the incredible sound they are able to produce.