When you hear this siren at noon the first Monday of the month, you don't need to worry.
It's the monthly exercise of the Dutch national emergency signalling system.
These electronic devices can produce other sounds as well, like voice messages. And they can target a specific area with a relevant message. This in contrast with the old sirens, that produced the classic air-raid warning, and could only be switched on for large parts of the country. Which made perfect sense during the Cold War and expected atom bombs.
More (and less grim) items to come in this section.