How many Hz is a train horn?

INNACCURATE FREQUENCY RATINGS A typical bass train horn is in the range of 277-494hz (C# (3rd)–B (4th)). The Nathan AirChime K-series (most popular authentic train horns) are in the range of 311-622hz. Most high-pitch small size horns are in the 740-1975hz range.



A standard North American train horn is not a single frequency but a chord typically composed of three to five different notes designed to be dissonant and attention-grabbing. According to Federal Railroad Administration (FRA) standards, these notes usually fall within the range of 250 Hz to 600 Hz. For example, a common "K5LA" horn (a standard on many freight locomotives) produces a five-note chord with fundamental frequencies around 311 Hz (D#4), 370 Hz (F#4), 415 Hz (G#4), 494 Hz (B4), and 622 Hz (D#5). The length of the "bell" on the horn determines the wavelength and thus the pitch; longer bells produce lower frequencies. These frequencies are specifically chosen because they are low enough to penetrate through car windows and buildings but high enough to be heard over the low-frequency rumble of the locomotive engine itself. In the UK and Europe, horns often use a "Two-Tone" system (High/Low) where the frequencies are distinctly separated to create a clear "warning" sound that is recognizable across different rail networks.

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As you saw from the DJD Labs test above, actual huge cast-metal locomotive horns top out at 149.4 decibels. Do you think a little electric horn or air horn can do more than 150 decibels? To put things in perspective, a firecracker or a shot from a rifle is around 150 decibels.

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If a sound is 100 dB at the source, it will be 94 dB at 1 meter, 88 dB at 2 meters, and so on. Therefore, you will generally be able to hear a 100 dB sound at a maximum of 16 meters.

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Anyway, don't blame the engineer: They're required to blow that horn. The regulation in question is called the Final Rule on the Use of Locomotive Horns—a name that strongly implies they've had just about enough of your bitching—and it requires four blasts 15 to 20 seconds before every crossing.

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The reason that trains honk their horns so much at night is because it's dark and the trains aren't so easy to see. Even though the lights are on, we sometimes can't see them coming, especially around the many blind curves near or ahead of the train station.

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If you hear, two small horns, it means the motorman is asking the guard to direct the railway signal to start the train. In case you hear three smaller horns, it suggests that the motorman has lost control over the train. This also acts as a signal to pull the vacuum break immediately. This signal is rarely heard.

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While owning and installing an aftermarket air horn or train horn is not illegal, some states have periodic inspections that your vehicle has to pass.

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This rule applies 24 hours a day, even if a crossing is equipped with lights, bells and crossing gates. Train crews also may deem it necessary to sound a horn as a warning when there is a vehicle, person or animal near the tracks.

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Reduced traffic: During the nighttime, there is generally less road traffic and fewer other trains on the tracks. This allows trains to move more efficiently and with fewer delays, as they encounter fewer obstacles and can maintain a consistent speed.

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Two short whistles mean that the engineer acknowledges that he or she heard or saw a signal that affects movement. Three short ones mean that the engineer intends to make a reverse movement. Two long, one short and one long mean trains are approaching a highway or street crossing. And the list goes on.

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In a quiet zone, railroads have been directed to cease the routine sounding of their horns when approaching public highway-rail grade crossings. Train horns may still be used in emergency situations or to comply with other Federal regulations or railroad operating rules.

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