Commonly found on large semi trucks, trains, and fire engines, pneumatic air horns use pressurized air to create loud, no-nonsense warning blasts that signify you mean serious business.
In this article, we'll take a look at how air horns work and we'll look at some that can be installed on your own vehicle. These air horns are easy to mount under the hood or on your roof, depending on application. Once fitted, they'll create the same level of sound found on the big rigs.
In our Air Horns section, you'll see multiple check boxes that allow you to narrow your product search by one or multiple preferences.
How Air Horns Work
Air horns work by using pressurized air to vibrate a diaphragm located within a compression chamber. This chamber is kept pressurized to ensure the horn sounds instantly. When activated by a switch or button, a valve opens allowing air to escape out of the compression chamber and into the base of the horn (known as the "throat").
Once air exits the compression chamber, the diaphragm starts vibrating and high-pressure sound waves are produced. As those sound waves pass from the narrow horn throat to the wide, flared-out horn mouth, they're amplified.
Air horn setups usually contain multiple horn pieces that emit sound. Because these pieces are trumpet-shaped, we'll refer to them simply as "trumpets". For example, kits we offer contain between 1 and 5 trumpets. Most of them also include a small air compressor. This detail will be noted on the product page.
Air tanks store a large volume of pressurized air that’s essential in creating a deeper, more forceful horn blast found on heavier-duty kits such as train horns and some truck horns. Typically, these kits include an air tank – however, if you should need to purchase one individually, we offer a variety of stand-alone compressors, air tanks, and more.
Measurements Of Sound
Loudness and pitch are the most important elements of an air horn's sound. Whenever possible, we've included a short audio sample of each horn - denoted by a "Sound" click button within product pages or product options.
On each of our product pages, you'll also see a decibel (dB) rating for how loud a particular horn is. Typically, train and truck horns range from 110 to over 150 decibels (db). For perspective, the quietest sounds a human ear can detect are 10 dB. Conversely, sound begins to become painful in close proximity around 130 dB.
Frequency of sound, known as pitch, is measured in hertz (Hz). Higher-frequency sound wavelengths are more compressed, traveling only a short distance between each wave. Low-frequency sound waves travel a greater distance between each wave. Horns that produce lower frequency waves have a lower pitch that's deeper and more baritone. The human ear can detect pitch levels from as low as 20Hz up to 20,000Hz.
As a general rule, trumpet length has an effect on the sound wavelengths and pitch emitted. Longer-length trumpets produce lower-pitch sounds, while shorter-length trumpets produce high-pitched ones (visualize the very short funnels on compressed air canisters used at baseball games). To create a richer chorus of different notes, air horn assemblies often feature multiple trumpets of different lengths.
When determining the distance that sound waves will travel, volume has a much greater effect than pitch does when traveling through unobstructed air. However, sounds with a low frequency pitch are more effective at traveling through solid barriers such as glass and walls. So if you're inside a car or a building, the sounds from a baritone train horn are more likely to reach your ears than those produced by high-pitched air horn of the same volume.
Air horns on most 18-wheelers don't have their own built-in compressors. Instead, pressurized air from the vehicle's own air brake system is used. Thus, drivers may pull a ceiling-mounted cable inside the truck to open a valve on the airline leading to roof-mounted horns directly above. Some trucks use buttons in the center of the steering wheel instead.
If your vehicle doesn't have its own airbrake system, don't worry. We've got you covered with truck horns that include their own built-in compressor. For example, there's the Wolo Road Warrior Roof Mount Truck Air Horn, the Wolo Challenger Roof Mount Air Horn, Wolo Big Bad Max Air Horn, and Kleinn Direct Drive Air Horn Kit just to name a few.
Train horn blasts are richer and more baritone because they use multiple trumpets of varying pitch, where each trumpet is larger with a heavy-duty diaphragm. Because the blast is a deep, forceful one, they typically require an air tank reservoir for added air volume as well as their own compressor. Kits we sell include their own compressor and, in most cases, an air tank also.
If you're seeking a sound that's more akin to a vintage air whistle, we've got "wolf whistle" horns from Vintage Parts and Trigger Horns. Because these horns pipe into your engine vacuum lines for pressure, they can be mounted anywhere you prefer - under the hood, or on the vehicle. They're great fun for classic hot rods, Model T's, and just about any car or truck.
Fans of the tune "Dixie" will appreciate the Trigger Horns Southern Belle 5 Trumpet Dixie Horn Kit. We've also got the Spec-D Music Air Horn that plays the riff from "La Cucaracha". Both of these kits come with their own compressor. And if you appreciate the look of carbon fiber, we've got the Wolo Bandito Carbon Fiber Trumpets Air Horn.
Installing an air horn is simple. Detailed instructions from the manufacturer will guide you through each step, from mounting to wiring. Click here to see one sample of installation instructions.
We also invite you to browse other air horns we offer - many of which are equally capable of creating truck and train level sounds. One thing is for certain: once your air horns are installed, there will be no mistaking the sound of your ride coming down the road!