Train whistle

Modern diesel and electric locomotives primarily use a powerful air horn instead of a whistle as an audible warning device.

The need for a whistle on a locomotive exists because trains move on fixed rails and thus are uniquely susceptible to collision.

This susceptibility is exacerbated by a train's enormous weight and inertia, which make it difficult to quickly stop when encountering an obstacle.

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.

This whistle produced a bright G-major 6th chord (GBDEG) and, again, was heavily imitated, copies being made by many different railroads.

But the most beloved of all three-chime train whistles to the public and railroaders alike were the deep-chorded "steamboat minor" long-bells.

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.

[2][3] However, one Federal Railroad Administration study has shown that the frequency of grade crossing accidents increases in areas where quiet zones are in effect.

[4] For instance, it was during the same period that locomotives began sporting the now crucially important tri-lamp headlight arrangement ("ditch lights") and reflector strips similar to those commonly found on highway tractor-trailers.

[9][10][11][12][13] Quiet zones are created in municipalities where citizens of the community complain of the noise pollution from the increasing number of trains which decreases their quality of life.

One of two (front and rear) whistles on steam locomotive 60163 Tornado
An air whistle mounted on a British Rail Class 483 EMU working on the Island Line . The whistles on the Class 483s were used by the previous Class 485 and 486 units and even the Class 71 locomotives and were fitted to the Class 483 units when the trains were rebuilt from 1938 tube stock in 1989.
GWR twin whistles, seen on 7827 Lydham Manor