Train whistle
From Wikipedia, the free encyclopedia
Train whistle, (originally referred to as a steam trumpet), is an audible signaling device on a train, locomotive, or the like, which produces a loud sound to warn that a train is approaching, and to communicate with rail workers. During the era of steam locomotives, the whistles were steam whistles, arranged to play a minor seventh chord.
Presently train whistles operate on compressed air, and thus, like the steam calliope which also evolved into a compressed-air instrument, the steam whistles on trains have given way to whistles that operate on compressed air. Train whistles that operate on air are sometimes called "airchimes". It is a kind of Airhorn
Most modern train whistles include exponential horns in order to more efficiently couple the modern compressed-air whistles to the characteristic acoustic impedance of free space. Train whistles that include such impedance matchers are sometimes referred to as train horns, owing to the horn-shaped neck and mouth of the air trumpet.
The older steam whistles were almost always actuated with a pull cord (or sometimes a lever) that permitted proportional (tracker) action, so that some form of "expression" could be put into the sound. Many train operators would have their own style of blowing the whistle, and it was often apparent who was operating the locomotive by the sound. Modern locomotives, however, often use a pushbutton switch, which takes away the fine control over the way the whistle is sounded.
Because trains generally have extremely high mass and relatively low braking friction, they are inherently difficult to stop at normal speeds. Since train whistles are extremely inexpensive to institute compared to other more effective warning devices, the use of loud and distinct train whistles have become the preferred safety fallback for railroad operators.
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[edit] History of train whistles
John Holliday describes the history of train whistles as originating in 1832, by way of a stationmaster at the Leicester and Swanington Railway opening, that the trains should have an audible signaling device. A local musical instrument builder was commissioned to provide a steam-powered whistle, then known as a "steam trumpet". Other designs had the steam whistling through a circular The article describes also a train-bus collision arising from a train that used truck horns instead of the standard whistle. Although the bus driver heard the horn, he thought it was a truck rather than a train.
American 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 which is full of dissonance, allowing it to have a distinct, frightening, and serious sound, rather than a happy one.
Among the most common musical chords on trains today in North America is the Airchime version of D#, F#, G#, B, D#, which is a G# minor 7th in the 2nd inversion. (G#m7/D#) Here's a soundclip of this familiar chord: Airchime K-5la(Horns Inc.)
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.
[edit] Noise complaints from train whistles
It is not uncommon for the sound of a train's whistle to resonate for miles; yet operators of the vehicles still have a difficult time hearing the warning signal due to the vehicle's soundproofing and ambient noise within the cab (such as engine, road, radio, and conversation noises).
The need to blare a train's whistle excessively loud to be heard by the driver of a vehicle approaching a grade crossing has become a major disadvantage to the use of train whistles as a safety device and has caused much controversy to those living within earshot of the train's whistle. It has been documented that a train's whistle, when operating on compressed air, driving an exponential horn, has been measured at a higher decibel levels within the homes of nearby residents than within the cab of a vehicle sitting at the grade crossing [citation needed]
Given the tonal design of the train whistle, the sound level, how often trains pass through given community, the number of grade crossings in proximity, and the time of day (night) of occurrence, some feel that train whistles have a serious detrimental effect on the quality of life of community residents in a given area despite the gain in safety that sounding the horn provides to motorists. However, studies have shown that the frequency of grade crossing accidents increase in areas where quiet zones are in effect.
Conversely there are those who do not object to the train whistle, as they believe it provides an important safety feature. Some people even like the sound of the whistle, as it calls to mind a nostalgic era, as with the riverboats and their steam whistles and calliopes.
[edit] History of the Doppler effect
It is train whistles that led to the discovery of the Doppler effect. At the time, trains were one of the few objects that would move quickly while playing a relatively constant (though not single-note) sound.
[edit] 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 (if moving), or apply air brakes and equalize pressure (if standing)
- 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. Known in railroad rulebooks as rule '14L'
- 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.
[edit] Other whistle code
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.
In Norway, for example, the following whistle signals are used:
- One short: Stand by or general acknowledgment.
- Two short: Apply/increase manual brakes.
- Three short: Apply manual brakes to stop the train as soon as possible.
- One long: Approaching railroad station or blind curve.
- One long, one short: Decrease manual brakes. When repeated, decrease brakes fully.
- One long, two short: Prepared for change of tracks, crossing and/or other situations that necessitates a gentle approach.
- Multiple short: Danger.
In Finland, the following are some of the signals used:
- One short: Engine is starting forward.
- Two short: Engine about to run backwards.
- One long, one short: Warning, used before arriving to a crossing.
- Three long: Danger.
[edit] 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.
[edit] The melancholy nature of train whistles
In popular and folk culture, train whistles are often associated with loneliness or hard luck, because of the association of trains with transients and hobos who often wait outside the train station and run and jump on to ride the railcars as they just begin moving out of the station. The book "Hear That Lonesome Whistle Blow" is an example.
Furthermore, minor chords (like that of a train whistle) are said to have a melancholy sound. Additionally, steam whistles (the traditional sounding mechanism of train whistles) tend to waver in pitch, and thus make more of a crying or wailing sound, that further adds to the lonesome nature of the whistle. Even the modern compressed-air whistle wavers in pitch much more than does a car horn, and the sound of the whistle is more "throaty" and windy (more like a pan flute or calliope) than other signalling devices like automobile horns.
Lastly, train stations were (and, to some degree still are) associated with the departure of loved ones, and the sadness of saying goodbye. To the extent that the sound of a train whistle is unique, and somewhat symbolic of long distance travel, it has come to contextualize itself as mournful and melancholy.
[edit] Whistle posts
A whistle post is a sign marking the location where a driver needs to sound the train whistle. Whistle posts are generally located near crossings.
[edit] External links
[edit] Sites explaining how to build or purchase toy train whistles
- make your own Quad Whistle
- Pneumatic Train Whistles
- Eight inch dual tone handmade train whistle
- Yosemite Valley Railroad Co. Products
- All about Steam Whistles and their Design
