What happens to the sound of a train whistle?

You may have noticed that a train whistle gets lower as it passes you. The whistle is not changing pitch, but you are hearing a change. This principle is known as the Doppler effect. The Doppler effect is named after the Austrian physicist, Christian Johann Doppler, who discovered it.



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Its primary purpose is to alert persons and animals to an oncoming train, especially when approaching a level crossing. They are often extremely loud, allowing them to be heard from great distances. They are also used for acknowledging signals given by railroad employees, such as during switching operations.

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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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One short whistle means STOP. One long whistle (three to 10 seconds) means the train is approaching a station. 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.

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Today, the only whistle signals you're likely to hear regularly are the grade-crossing warning (which is also often used to warn employees or others on the tracks); two (or three) shorts to indicate the engineer has received a signal to start the train forward (or backward); and one long blast when a train is ...

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It is a safety necessity. Train horns are not to wake people up from their sleep. It is a safety issue. It is also a federal law that trains must sound their horns as they approach a grade crossing.

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The maximum volume level for the train horn is 110 decibels, and the minimum sound level is 96 decibels.

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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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As a safety feature to warn anyone crossing the line on foot/in a vehicle (or near the railway) that there was a train approaching them. This includes areas where shunting is being carried out (such as in a freight marshalling yard).

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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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It is the standard signal used when the train is about to move forward. Two long blasts of the horn are for warning anyone near the train that it is about to move forward. There are other standardized horn signals like three short blasts for the train about to move backward.

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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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A train driver, engine driver, engineman or locomotive driver, commonly known as an engineer or railroad engineer in the United States and Canada, and also as a locomotive handler, locomotive engineer, locomotive operator, train operator, or motorman, is a person who operates a train, railcar, or other rail transport ...

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To run train (or run a train) refers to when multiple men have sex with a woman one after the other, with or without consent.

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