The humble horn is an often overlooked part of a boat’s safety critical systems, yet having a means of making an adequate audible warning signal is not only a requirement under both international and local maritime laws; it’s also prudent if you care about your own personal safety as well as that of your passengers/crew.
Many boats come shop fitted with a fairly puny and pathetic buzzer type horn which might not make enough of an impact when trying to warn others of your presence. For me it’s important to fit a horn that emits the loudest and most jarring sound possible.
Remember the aim isn’t to make music here, we want to warn others of potential danger!
What Are The Different Types of Horn? Advantages and Disadvantages of Each
Air Horns
Air horns, as the name suggests, utilise compressed air to generate the sound emitted by the horn. Air horns are typically capable of producing the loudest noise of all, with some models capable of producing around 125dB, which would be described as ‘extremely loud’ by most sound safety literature, and is equivalent to something like a jet aircraft starting up or a balloon popping.
Air horns have a tube with a trumpet like end to them to emit the sound they produce. The longer this part is, the louder, and usually deeper the sound is.
The air used to generate the sound is produced by an electrically driven compressor which is usually positioned below deck.
Advantages
As mentioned above air horns offer the loudest output sound of any horn. As you can imagine the greater the air pressure driving the horn, the louder it will be. The loudest air horn systems are typically driven by a compressor that produces 120 PSI or more.
Air horns are also available in dual units with two trumpets next to each other. These are a superior option if you can afford it because the two notes produced (usually harmonically dissonant, ie notes that do not sound good together)
Disadvantages
Not an issue with air horns per se, but certainly all horns that use a trumpet type emitter; something I’ve come across over my years in the boat building industry, trumpet horns have a nasty habit of filling up with water when a large bow wave reaches the horn.
This can lead to corrosion or failure of the horn, so it’s not ideal. Ideally the horn should be mounted such that it is angled slightly downwards so that any water will quickly drain out of the horn.
Installation/Maintenance Notes
Besides mounting the horn at a slight downward angle, it best if you can keep it as high as possible to avoid salt spray.
Compact Horns
Compact horns are much like those found on a car; electrically powered, and essentially using the same principle of a vibrating metal diaphragm that a speaker uses, albeit in order to produce a single note only. It’s a simple tried and tested principle.
Advantages
As the name suggests, compact horns take up a lot less space than trumpet horns, so if you’re short of real estate on your mast, and don’t want your boat’s lines spoiled by a big trumpet they can be a great option. They also don’t have any of the water retention issues of trumpet horns either.
Disadvantages
There is a limit to how loud a compact horn can be, unlike air horns which can reach sound levels of up to 125dB, compact horns typically kick out 107-109dB, while the most optimal designs (those that include a snail shell like acoustic chamber) are capable of producing 115dB.
If you’re after a classic ‘honking’ sound, compact horns might not be the best choice either. This method of producing and amplifying sound means that you get more of a loud ‘buzz’ or ‘beap’. This is perfectly acceptable from a legislative point of view of course, it just doesn’t quite hit the spot!
Installation Notes
Again if you can mount your compact horn such that it won’t be affected by salt spray that will help prolong its life.
Electric Trumpet Horns
These are more or less a hybrid between compact horns and air horns, taking advantage of the sound augmenting properties of the trumpet feature of an air horn, but with the convenience of generating the sound electrically.
Advantages
If you like the visual appeal of a big shiny trumpet on the side of your boat and want to keep things strictly electrical then an electric trumpet horn is for you.
In terms of sound, they produce a tone somewhere between the blast of an airhorn and the buzz of a compact horn, so not a classic horn sound, but not too far off.
Disadvantages
Electric trumpet horns aren’t a great deal louder than compact horns, with most on the market producing a similar decibel level, so there isn’t really any great advantage in that respect.
Installation Notes
Like trumpet air horns, electric air horns can suffer from collecting water in challenging sea states or when there is a lot of spray. If you think this is going to be an issue you’ll want to mount the horn angled a few degrees towards the ground to prevent water from pooling in the trumpet.
Flush Mounted ‘Drop in’ Horns
These use the same basic inner mechanics as compact horns but are designed to be mounted in a ‘thru-hull’ configuration, so what you see on the outside of the boat is basically a flush mounted grille, while the rest of the horn is hidden internally.
Advantages
Flush mounted horns are by far the sleekest option available, and given that nothing is ‘sticking out’ on deck there isn’t any risk of accidental damage. It’s quite common to see flush mounted horns on smaller boats with a small or non existent mast to mount a compact or trumpet horn.
Disadvantages
If you’re retro fitting a flush mounted horn it will mean cutting a convenient hole in the deck somewhere. This might be less appealing than fitting a compact horn for some, and if the idea makes you feel faint then it probably isn’t for you!
Installation Notes
Besides cutting a hole in the deck (and ensuring you’re happy with the position before you cut!) you’ll also need to be prepared to run cabling from a potentially awkward position inside the boat to your distribution cabinet, whereas a horn on the mast can take advantage of the established route taken by other equipment.
Hand Held Air Horns
If you’re looking for a horn that meets the legal obligation to carry an audible warning device without any of the cost and finesse of any of the above options, then you could simply keep a hand held air horn on board your boat.
Advantages
Hand held air horns are comprised of an aerosol can full of compressed air and a plastic trumpet mounted on top, and that’s it! As such no installation work is required making them a very attractive option, particularly if your use of the horn is limited strictly to emergencies only
Hand held air horns are available in both refillable and non refillable varieties, but never cost more than about $40 a time, so replacing them after a few years is never going to be a big deal.
Disadvantages
I think there’s a lot to be said for having a hard wired system in place that you can operate at the push of a button whilst stood at the helm. Unless you make sure to keep your hand held air horn to hand at all times you could find yourself scrabbling around to find it at a moment’s notice when in reality you might not have a moment to spare.
