also: しょうとうらっぱ
lights-out bugle call; taps; last post
A bugle or trumpet call signaling lights-out, used in military or camp settings. 消灯ラッパ is the common term; 'taps' is the US equivalent, 'last post' the British/Commonwealth equivalent.
At camp, when the lights-out bugle sounds, it's time for everyone to sleep.
In the military, you must be quiet after taps.