Train whistle

A train whistle is a signaling device, on a train, locomotive, or the like, that makes a loud sound to warn pedestrians and motorists that a train is coming and to communicate with railroad workers on a train.

Because trains have high mass, and low friction, they tend to have difficulty stopping suddenly, and thus a loud and distinct whistle is advantageous for safety.

Contents

1 Polyphony of train whistles 2 History of the Doppler effect 3 Whistle code 4 Train whistles in folk culture

Polyphony of train whistles

Train whistles usually have either three or four frequencies that are sounded together, at the same time, to form a chord. As compared with automobile horns, for example, which form a major third, usually with the notes "F" and "A", the train whistle usually forms a non-major chord, allowing it to have a distinct, and frightening, rather than happy sound.

A train whistle is usually low in pitch, compared to similar mobile signaling devices on cars, trucks, bicycles, etc. The low pitch helps us mentally connect with the fact that the sound's source is large in size and weight.

History of the Doppler effect

It is train whistles that let to the discovery of the Doppler effect. At the time, trains were one of the few objects that would move quickly while playing a constant (though not single-note) sound.

Whistle code

Train whistles are used to communicate to other railroad workers on a train or to railroad workers in the yard. Different combinations of long and short whistles each have their own meaning. They are used to pass instructions, as a safety signal, and to warn of impending movements of a train. Despite the advent of modern radio communication, most of these whistle signals are still used today:

• One short: Stop or stopping; apply the brakes
• One long: Approaching railroad station or junction
• Two short: A general answer signal or acknowledgement; identical to the "roger" or "10-4" radio terms
• One short, one long: Inspect the train
• One long, one short: Visibility obscured
• Two long: Train is about to proceed forward; release the brakes
• One long, two short: Additional section follows signaling train
• Two long, one short or two short, one long: Train is approaching a meeting or waiting point
• Two long, one short, one long: Train is approaching a grade level crossing (i.e. a road crossing). This is a widely used safety signal used to warn motorists and is blown at every grade level crossing, except where local noise ordinances prohibit it.
• Three short: Train is about to proceed in reverse (if standing), or train is about to stop at the next station (if moving)
• Three long: Train cars have come unhooked; train has come apart
• One long, three short: Flagman, go protect the rear of the train
• One short, three long: Flagman, go protect the front of the train
• Four short: Request for signals
• Four long: Flagman, return to the train from the west or north
• Five long: Flagman, return to the train from the east or south
• Four short, one long: Fire alarm; fire on the train
• Multiple short: Danger, get off the tracks! Used to warn pedestrians or livestock who are on the tracks in front of the approaching train.

Not all railroads use the exact same whistle signals or assign the same meanings. Some railroads will use their own variations of the above. A few of the signals are obsolete because the workers they were used to communicate with (such as flagman) are now obsolete.

Train whistles in folk culture

The well known song "Five Hundred Miles" makes frequent reference to the sound of the train whistle, as being audible over a great distance.

Excerpt:

If you miss the train I'm on,
You will know that I am gone.
You can hear the whistle blow a hundred miles,
A hundred miles, two hundred miles, three hundred miles, four hundred miles,
You can hear the whistle blow five hundred miles.

In popular and folk culture, train whistles are often associated with loneliness or hard luck, because of the association of trains with hobos. The song "Hear That Lonesome Whistle Blow" is an example.