汽笛

1. Origins, structure, and basic meaning

• Structure: 汽笛 is read as きてき and is a noun for the loud signaling whistle or horn of a train or ship.
• Basic usage: Identify the source with 列車の汽笛 or 船の汽笛.

2. Common pitfalls and similar expressions

• Translation follows the vehicle
  • Whistle suits the departing train, while horn or foghorn suits a ship sounding in a foggy harbor.
• Signal rather than engine noise
  • It is an intentional audible signal, not the general mechanical sound of a running engine.