[jerf]

"a) sound energy falls off as 1/r^2"

No, it doesn't. That's how it falls off when being transmitted perfectly spherically in an environment that won't reflect or refract anything. Consequently, this turns out to be a not-very-useful equation in practice. In particular ultrasound can be beamed just like light, making the "perfectly spherical transmission" not even a close approximation, just as it is not a good approximation for focused lasers. Our intuition doesn't support this because our hearing tops out at frequencies still low enough to do some significant bending around obstacles (though at the higher end if you pay attention you can tell they don't do it as well), so we don't have an intuition of sound acting like a beam, but it can.

There's more to sound than "basic physics", and what you learn in Physics 101 about sound is simplified to the point of total uselessness as in real-life you will never encounter a situation where the prerequisites are met for inverse square falloff.

Mind you, I'm still pretty skeptical, but not about the ability to beam sound. That's established engineering, not wild-eyed craziness.

[scottlocklin]

"In particular ultrasound can be beamed just like light, making the "perfectly spherical transmission" not even a close approximation"

You do realize that energy from a point source of light also falls off like 1/r^2, right?

[jerf]

OK, since conversation has moved on, let me be blunt: You don't know what you're talking about. Your physics 101 education is not the end-all, be-all of physics, and what "point" transmission does doesn't matter because we aren't talking about points. You are in no position to be lecturing people about physics; you are in a position to be lectured to about physics.