long story short, my understand of Ultrasound is:
If there is a big enough hold or gap, I can "see" through it (up to 50m radius, of cause).
The opposing side believe that:
Ultrasound ruquired "LOS". If something is is the middle between you (with ultrasound) and the object, you can't "see" it.
Just want to know, which one is corrent?