Aquinas' definition. The Oxford Concise Dictionary of the Christian Church defines acedia (or accidie) as a state of restlessness and inability either to work or to pray. Some see it as the precursor to slothâone of the seven deadly sins.
A train horn is a powerful air horn that serves as an audible warning device on electric and Diesel locomotives. The horn's primary purpose is to alert persons and animals to an oncoming train, especially when approaching a grade crossing. The horn is also used for acknowledging signals given by railroad employees, such as during switching operations.
As the train approaches, the sound of its horn is heard at a high pitch and as the train moved away, the sound of its horn is heard at a low pitch. This is the Doppler effect. A common Physics demonstration the use of a large Nerf ball equipped with a buzzer that produces a sound with a constant frequency.