I dont see this working on significant fires. Let it run, separate flame from fuel, but what happens a few seconds later? The fuel is still there, the heat is

I dont see this working on significant fires. Let it run, separate flame from fuel, but what happens a few seconds later? The fuel is still there, the heat is still there, as soon as the sound stops it will reignite. Water/foam and such create both a physical barrier and immediate cooling to prevent reignition. As a general rule, cooling any situation involves throwing cold stuff at the hot stuff. We have many means of projecting heat, but no way to project 'cold' without throwing cold stuff.