Although the last few days have brought Germany's 1940 invasion into Denmark back into focus, the alarm you are likely to hear on Wednesday is not a sign of impending doom but rather an annual exercise carried out by the Danish Emergency Management Agency (DEMA).
Every year since 1994, DEMA has tested the nation's siren warning system on the first Wednesday of May at 12pm.
DEMA's system encompasses 1,078 sirens that cover around 80 percent of the population.
“The sirens are just one part of our whole warning system. There are several ways for authorities to reach residents in emergency situations, including the media, and social media channels like Twitter and Facebook. We are even currently working on an app,” Colonel Henrik Andersen from DEMA told The Local.
“It's an old school system but it still has a clear function. Technology can go down, but the siren system is on an independent power supply allowing it to work even during a power outage,” Andersen added.
DEMA said that the alarm system is used locally and regionally several times a year. In 2014, for example, the system was used 24 times, mostly to warn about fires. In eight of those cases, the sirens went off.
When the alarms go off on Wednesday, you can just sit still. In a real emergency, you should go inside when you hear the signals, close your doors and windows, turn off your ventilation systems and turn on either public broadcaster DR or TV2 for further instruction.
On Wednesday, there will be two signals. The first is a sound that rises fast and then slows down gradually. It will be sounded four times over a period of 45 seconds and then repeated.
The second signal will be one long uniform tone lasting 45 seconds to signal that the danger – or in this case, the harmless test – is over.
You can hear the signals here.