Being that the moment of silence, as observed by the State of Israel on both Yom Hashoah and Yom Hazikaron is so rarely observed at a national level, though it is observed more commonly at small local and personal levels, one wonders how it came to be that the State of Israel decided to employ the siren with the minute (or two, on Yom Hashoah) of silence..

Here is the background, according to The Jewniverse:

You might be surprised to learn that it actually dates back to 1918 South Africa, when the mayor of Cape Town initiated the Two Minute Pause to remember the fallen soldiers on Europe’s World War I battlefields.
Another South African, the politician and author Sir James Percy FitzPatrick, was in England when the war ended. He had lost a son in battle the previous year. He suggested to King George V that they also adopt a moment of silence. It became part of Armistice Day events throughout the British Empire.
The tradition was imported to Palestine, which the British ruled from 1918 until Israel was established in 1948. The British installed air-raid sirens across Palestine at the outset of World War II. At first, the new State of Israel used the sirens for ceremonial purposes only sparingly: when Zionist leader Theodor Herzl’s remains were flown in from Austria in 1949, and after a 1948 massacre on a kibbutz.
In 1951, the Rabbinate established Yom Hazikaron, Israeli Memorial Day on the day before Independence Day. In 1959, the Knesset mandated Yom Hashoah, Holocaust Remembrance Day. Both have been marked by sirens — and silence — ever since.

I am not complaining, but I never really understood why Israel kept so many of the rules and processes that had been in place from the Brits and from the Turks. Anyways, that's the interesting background to the Yom Hashoah and Yom Hazikaron sirens.