Some 80 years after the start of World War II, many of us whose parents may not even have been born yet are familiar with the sound – a slow droning noise getting ever closer, ever louder, and deeper in pitch. It's the sound of a plane falling to earth, but it was first associated with a very specific plane, for a specific reason – the Nazi Luftwaffe just wanted to scare the bejeezus out of English and Russian civilians.
At the start of World War II, the Junkers 87-B dive bomber was the Nazi's first mass-produced fighter aircraft, already perfected in the Spanish Civil War and ready to take on the French, British, and later, the Red Army. Nicknamed the Stuka (from the German word for "dive bomber"), the Junkers 87-B would become the iconic Nazi warplane. It was less about its ability in the air (which was top of the line for the time) it was because of the sound the dive bomber made when zooming toward an earthbound target. The Nazis called it the "Jericho Trumpet" – and it was totally unnecessary.
It was all for a propaganda effect.
You can hear it just watching this gif.
Siren devices were attached to the wings' leading edge just forward of the Stuka's fixed landing gear. The sound was meant to be memorable, weaken the morale of the enemy, and cause mass fear of the German dive-bomber. It was so effective the sound became associated with the fast Nazi blitzkrieg across Europe and feared the world over, even across the Atlantic where newsreels entranced the American public.
The only problem with the Jericho Trumpets was that they affected the aerodynamics of the Junker 87-B, causing enough drag to slow the plane down by 20 miles per hour and making them easier targets for defenders. Eventually, the Sirens would be scrapped, and whistles were placed on the bombs to create the same psychological effect.