1 bang per hour
The Gunpowder candle. A way of telling time based on one of the oldest methods to do so. In ancient times, some candles would have markings next to them that were used to tell the time when the burning time of that candle was known.
This candle works according to the same principle, but with a carefully calculated amount of gunpowder that creates a bang every hour. This is of course just enough so that it generates an audible bang but does not blow the candle to pieces.