The mystery of the strange sounds and 1 extra theory.+

A.D.A.D - Short for (Area Directed Acoustic Device)

Normal L.R.A.D sound weapons create long range sounds, but those are direct on target they can not circumvent walls,roofs etc.

This new weapon can somehow direct tones in selected areas, through walls roofs concrete,steel,wood as if there was no hindrance/barrier.

If this is the case then it is a very high tec weapons system being used from the surface or from the sky/space.

Just an idea, you know it never hurts to broaden the perspective, we have to cover every angle.