Why Israel is breaking the sound barrier in Lebanon

Late Saturday night, several residents of southern Lebanon repeatedly heard Israeli fighter planes breaking the sound barrier in the sky above them. A noise was also heard in other regions of Lebanon such as Beirut, Chouf and Mount Lebanon. On Sunday, the roof of a house collapsed in Nabatieh after an Israeli plane broke the sound barrier. A mother and her son were injured and hospitalized.

So what is this technique and why does the Israeli air force frequently use it? Khalil Helou, retired general of the Lebanese army and vice-president of the Lebanon-Message association, spoke with L'Orient-Le Jour about this tactic.

What does breaking the sound barrier physically entail?

Normally, an airplane flies at a subsonic speed, that is, below the speed of sound, which is about 340 m/second, or more than 1,200 km/h. When an airplane makes noise, it emits waves that accumulate around it. When the pilot accelerates and exceeds the speed of sound, he breaks these waves in a way. This is what creates a noise similar to an explosion. This explosion can break windows, knocks over objects ... It is like an extremely fast gust of wind, which lasts less than a second.

The roof of a building even collapsed on Sunday in Nabatieh.

Normally this doesn't happen. If this roof has collapsed, it is because the building is simply not up to standard.

What is the range of the sound emitted?

The radius within which a sound barrier can be heard is only a few kilometers, no more than ten kilometers. If some Israeli pilots break the sound barrier in several places in Lebanon, it is either because they were ordered to do so or because they are having fun.

Why does Israel use this technique?

There are at least three reasons. First, the Israelis want to remind Hezbollah that they have air supremacy in the Lebanese skies. It is clear that this is the case, because until now, Hezbollah's surface-to-air missiles have achieved nothing, apart from shooting down a few drones. This is a way of maintaining deterrence.

The second effect is of course psychological. The aim is to demoralize the supporters of the party, to scare them.

But there is a third reason, more technical and less known: Breaking the sound barrier can help detect enemy radars. Hezbollah has radar systems that can detect Israeli planes or missiles by several means: heat, communications emitted ... but also sound. An Israeli pilot can therefore break the sound barrier to force the activation of a Hezbollah radar and thus detect this equipment and these communications or transmissions.

This article originally appeared in French in L'Orient-Le Jour.