AirChime — Train Horn Glossary

AirChime is the brand name of locomotive air horns manufactured by Nathan Manufacturing (now operating as Nathan AirChime under parent Nautilus Integrated Solutions). Nathan AirChime supplies more than 90% of America’s locomotive horns — both passenger and freight — making the brand effectively synonymous with “the sound of a North American train” in modern public consciousness (Nathan AirChime, official).

What “AirChime” means

AirChime is Nathan Manufacturing’s product line of locomotive air horns. The trademark is registered to Nautilus Integrated Solutions (Nathan’s parent), and aftermarket retailers like HornBlasters and Locomotive Parts Supply re-package or resell these OEM horns for vehicle install. Nathan does not sell direct to consumers — the company operates B2B through quote requests, primarily to Class I and Class II railroads.

Product series

Nathan AirChime ships four major series (Nathan AirChime, official; Wikipedia: Nathan Manufacturing):

• K series — kettle-drum double-diaphragm bell design, 1 to 5 chimes. Modern standard. Includes K3LA, K5LA, K5HL, K5LLA-R1, K5H, K5CA-LS variants.
• P series — older “P” platform, including P3, P5, P5A. Penn Central / Conrail-era horns; some still in service on heritage equipment.
• M series — discontinued; M3, M5 variants exist. The M5 is “the most desired horn by collectors” per Wikipedia.
• C series — large industrial / specialty applications.
• KSJ series — Nathan’s modern compact variants for shorter manifold space.

Why Nathan dominates the market

Several factors put Nathan at >90% U.S. locomotive horn share:

• Long-running cast-aluminum manufacturing with consistent quality across decades of production.
• Wide chord catalog. Each railroad can specify a Nathan K5 variant (LA, HL, LLA, H, CA-LS, etc.) that produces a different musical chord while sharing the same physical kettle-drum platform — useful for fleet identity.
• Replaceable bells. Individual bells (#1, #2, #3A, #4A, #5) can be replaced without retiring the manifold.
• OEM relationships. Nathan supplies Class I freights (Union Pacific, BNSF, CSX, Norfolk Southern, Canadian National), Amtrak passenger, commuter / regional operators (Metra, NJ Transit), and many short-lines.

Per the brand’s own marketing, Nathan AirChime claims “over 90% of America’s locomotive horns, for both passenger and freight applications” — see nathanairchime.com.

The Leslie alternative

Before Nathan’s K-series rose to dominance in the 1970s–80s, Leslie Controls was the other major North American locomotive horn supplier. Leslie’s flagship was the RS-5T Supertyfon, prized for its 144 dB output at 100 PSI (HornBlasters: World’s Loudest Train Horns) and audibility up to 3.5 miles. The Leslie RS3L was once the most common 3-chime horn on North American railroads.

Today Leslie horns remain in service on legacy locomotives but are increasingly rare on new equipment. Nathan AirChime has effectively replaced Leslie as the OEM standard for new builds.

Hearing AirChime horns

Almost any time you hear a freight or passenger train approach a grade crossing in the U.S., you’re hearing a Nathan AirChime horn — most likely a K5LA, given its >50% market share within the K-series. Listen for the B major 6th chord (D♯, F♯, G♯, B, D♯) that defines the K5LA. For an interactive synthesized version of multiple Nathan chords, see the train horn soundboard. For a real audio recording of a K5LA see the forthcoming K5LA sound library entry.

Aftermarket purchase

Nathan does not sell direct, but their horns are available through specialty retailers:

• HornBlasters — packages Nathan horns in complete vehicle kits with HornBlasters compressor + tank + valve. K5LA kit at $4,999.99–$5,199.99.
• Locomotive Parts Supply — sells standalone Nathan horns. K5LA at $1,649.95.
• Pure Diesel Power, Air Horns of Texas, Triplex Motorsports — secondary channels.

For a full review of the K5LA as an aftermarket purchase see Nathan AirChime K5LA Train Horn Review (2026).

Related glossary entries

• K5LA — Nathan’s most-installed 5-chime horn
• K3LA — 3-chime sibling of the K5LA
• Horn Pattern — the FRA grade-crossing signal sounded on AirChime horns across America
• Decibel — SPL unit used to rate AirChime output (K5 = 149.4 dB at 3 ft)
• PSI — air pressure (90–140 PSI typical for K-series) needed to drive the bells

Sources

• Nathan AirChime — manufacturer site (90%+ U.S. locomotive horn share, K/P/M/C/KSJ product series)
• Wikipedia — Nathan Manufacturing (chord configurations across K-series, P-series, M-series; K5 149.4 dB measurement)
• HornBlasters — World’s Loudest Train Horns (Nathan K5 149.4 dB ranking; Leslie RS-5T 144 dB at 100 PSI comparison)
• HornBlasters — Nathan Airchime Train Horns landing page (aftermarket Nathan kit catalog)
• Locomotive Parts Supply — Nathan AirChime K5LA (aftermarket retailer reference)
• SoundTraxx — Locomotive Airhorn History (industry context for Nathan K-series adoption)

We do not perform hands-on testing — see our methodology.