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.
To a person on the ground, the horn starts off high as the train approaches and then goes low as the train recedes. 1  As a car moves, sound waves in front of it get squished up while those behind get spread out. This changes the perceived frequency and we hear the pitch change as the car goes by.