Feasibility of Echolocating Rhinos Weaponizing Said Echolocation

Question

The title says it all. This question is about Rhydar, echolocating mutant rhinos, which are even more violent and aggressive than their conventional counterparts, specifically about weaponizing echolocation. There's been plenty in the media about sonic blasts, it's a pretty common form of weaponry. Pretty unrealistic, though, right? Not exactly.

As noted in scienceline.org, "The idea of the 'acoustic prey debilitation hypothesis' (also more charmingly called the “Big Bang Theory”) was first mentioned in a science magazine in 1963 and was the subject of a key review article by Kenneth S. Norris and Bertel Mohl in 1983.

The word 'debilitation' is appropriately vague. The sheer power of a sound wave can cause physical damage, like hemorrhaging. Or a sound could possibly confuse or disorient prey instead."

When it comes to sperm whales, well, their echolocation's volume tops out at 200 Decibels, much more than that of a jackhammer, and only 4 decibels away from the loudest sound ever recorded by NASA: the first stage of the Saturn V rocket. On land, that kind of sound would be slightly less powerful at 174 Decibels, but would still have enough power to rupture a man's eardrums.

I'm not content with that. Sure, confusing or stunning an opponent, as well as rupturing their eardrums, can be invaluable in combat, and is perfectly feasible considering law enforcement's current use of sonic weaponry, but I'd prefer a little something I call: sonic spear. This is a Rhydar's signature attack, a stream of highly focused sonic energy that can punch right through a brick wall, but is merely one example of their sonic arsenal.

My question is simple; How Can Rhydar Feasibly Weaponize Echolocation? I will appreciate answers, as this will help me determine the type and power of a Rhydar's sonic attacks, which are pretty essential considering its name and nature.

Further clarification:

I would appreciate answers that use infrasound (which, as I've discovered thanks to the comments, is already used as a weapon), as well as ultrasound (hey, it can be weaponized too), and if you can explain how a Rhydar could create and utilize a blast wave, hopefully as some form of the sonic spear, that would be even better. Thank you!

Answer 1

Getting 'sound', i.e. pressure waves to tear a hole in a wall, in air, will not work.

You either have a shockwave, like of an explosion, that will expand spherically, and thus not punch a hole, but rather tear down the hole wall if powerful enough, or you have normal sound, which will always have much less power than a shockwave, but can, instead, wreak havoc by being the harmonic to some natural vibration in the object. this is then not one harsh push like in the shockwave case, but rather a continuous 'feeding' of a vibration in the object, that finally lets the vibration cross some structural-integrity threshold, and destroys the object (like the opera-singer with the glass, in media, or the ultrasound with the gallstone, in reality).

Projecting onto something distant could be done by a phased array, so i see no theoretical problem there.

The problem is the so called impedance of solid things versus air. Sound has a hard time coming out of vibrating materials into the air (your rhino producing sound), and an even harder time getting back into solid materials (like the wall) - while the production can be solved by not going the vibrating-stuff route (as in a guitar), instead, for instance, using vibrating air (as in a whistle), the problem on the receiving end will not be solved as easily. Impedance is dependend on the specific frequency, so while for every target (dependent on size, structure, material, temperature) we might find some frequencies that have a good coupling factor, but this do not need to be useful/destructive frequencies.

Generally, air is a really bad destructive medium, because it is so very not-dense, airy, one might say. Energy is Force * distance, and the Force is in the sudden deceleration (a) of the air, scaling with a * m. Mass (m) is very low, and so we end up with miniscule amounts of energy transferred on each half-wave of a vibration - the only way to make this have an effect at all is, if all these micro-pushes' timings are finely tuned to some natural frequency of the target.

But even if you go 'ok. it's a rhino, let's go for wholesale destrucution - shockwave!', you are pretty much out of luck. A shockwave is initiated by an object moving faster than the speed of sound of that medium (possible, every whip-snap does it), but the power of said shockwave depends on the pathlength of this movement. An explosion can simply expand for as far as the explosion-gases will allow, but a rhino will only have a few cm (the forehead can pulse forward, say, but that's it) - so the shockwave might be shocking ('that rhino bangs!') but it will not even ruffle the grass after a few meters.

You can escape the coupling losses by directly touching the emitter to the target. Maybe even bury your horn in it? Then the rhino would begin 'singing' going up and down the scale in search of the best harmonic, zeroing in on it, then upping the volume until the target pops/crumbles.