Robert Swanson founded Airchime Ltd out of his British Columbia home making custom steam whistles.

There are countless horns on the market that claim to be train horns, but none can match the history, size, and volume of a Nathan AirChime Train Horn. For decades, railroad companies have trusted these horns to keep their conductors and haul safe, and now, you can install them on your ride!

Nathan AirChime Train Horns have been ruling the rails for longer than most of us have been alive. Back in 1953, Canadian manufacturer Airchime Ltd. refined its Nathan Truck Horn to be used on locomotives, resulting in the very first P-style Train Horns, also known as “The President’s Whistle.” These horns quickly took the rails by storm thanks to their incredible volume, low manufacturing cost, and minimal maintenance requirements. Over the years, the P-Horn has undergone various changes, with the three-chime P3 and the five-chime P5 being the most commonly seen today.

Shortly after the P-Horn’s introduction, the K-series horns made their debut in 1954. The K-Horn originally had a higher pitch than the P-horns and came in three-chime and five-chime versions known as the K3H and the K5H, respectively. Robert Swanson, the designer of both horns, believed the K-Horn to be the superior horn, with the P-Horn serving as a more cost-effective alternative. The “H” in both horn names originally stood for “High Pitch,” but now it stands for “High Bracket,” with the K5L having an “L” designator to indicate a “Low Bracket” style.

In the 1970s, Amtrak decided to bring the classic K-Horn to American rails. While they loved the overall sound, they wanted American train horns to have a lower pitch, so they altered the K5H's original D# minor 6th chord to a much brighter and cheerier B Major 6th. Around the same time, AirChime designed a new low-profile bracket to mount the horns on. With the new tuning and lower bracket, the K5LA was born, with the “L” standing for “Low Bracket” and the “A” designating American tuning. By the 1980s, the K5LA was the most popular horn used around the world and remains so to this day.

The P-series horns are another impressive offering from Nathan AirChime. They come in single tone (P1), three-chime (P3), and five-chime (P5) versions and are known for their sand-cast bells. The frequency ranges for these horns can vary from 220 to 554 hertz, making them incredibly versatile. Compared to the M-series, the P-series horns have longer bells and a heavier manifold.

The name of each horn in the P-series is determined by the placement of the bells. Each horn's name begins with a P, followed by the bells facing forward, and an R if any of the bells are reversed. For example, a P12345 is a true five-chime horn with all bells facing forward, while a P135R24 has bells 2 and 4 reversed. Regardless of the specific configuration, the P-series horns offer unmatched sound and power, making them a popular choice among train horn enthusiasts.

K series horns have many different eras and over time the notes were sharper or more flat.

In the beginning of The K series family in the 1950’s there was just the K3H and K5H which at the time had Adjustable backcaps with ”AIRCHIME“ on them. They were sandcast and sounded mellow, very close to a steam whistle which is what Robert Swanson originally intended.

When the introduction of the 3A and 4A bells in 1975 which would lead to the creation of the K5LA and K3LA they would be distinguished by their Big Tag which gave them the name of “Big Tag” Horns. Many of these horns played notes that were close to the intended and also not.

Wide Front Horns are from the 1980’s and are distinguished by the 3O1O9 on the back caps. Wide Front Horns usually play flat notes, but sound very sharp. For example the Wide Front K3LA/HA would play the E, G, C notes.

Narrow Front Horns started production in 1989 and were distinguished by the 30109 on the backcaps. A lot of the Narrow Front horns play chords similar to the Wide Front but as time went on they started to sound harsher. When the Raised Letter Horns started to pop up they still had the Narrow Front Backcaps until 2013 or 2014.

Raised Letter horns started production in 2005 or 2006 where Micro-Precision bought Nathan Airchime. Raised Letter Horns are distinguished by the “AIRCHIME” lettering on the side of the bells, and a lot of the early Raised Letters had Narrow Front 30109 backcaps until 2013 or 2014 as mentioned above. However newer Backcaps were made with a similar design to the older style Backcaps before the Wide Front design. Raised Letter Horns are also designed to play the intended notes of the horns they were meant to play originally. The Raised Letter K5LA/HA aka ”3rd Gen K5LA“ to railfans has a very high pitched sound to it because of the 5 bell, which has more prominence than that of K5LAs prior; this goes for the Raised Letter K5L/H as well. The KS-3A bells on Raised Letter K5LAs also tend to be sharp to some degree, playing closer to an A note instead of a G# note (forming a B7 chord instead of the intended major 6th), hence the name. The Raised Letter K3LA/HA and K3L/H sound Very close to their original intended chords. However both the Raised Letter K3LA/HA and K3L/H sound very similar to Leslie’s S-3K/RS-3K and the Prime-990 a copy of the Leslie S-3K with some notable design differences. This makes the sound of the Raised Letter K3LA/HA and K3L/H and other Raised Letter Horns very different from their predecessor K horns.

Raised Letter horns, especially Raised Letter K5LAs, are often derided by railfans for sounding very unpleasant when compared to the older horns. Some have said there is an FRA regulation mandating Raised Letter horns on the belief that unpleasant-sounding horns get more attention.