Sonic Cannon

[teenagefurball]

How would one go about creating a sound cannon capable of breaking through rock

[Qfwfq]

How would one go about creating a sound cannon capable of breaking through rock

Simply by placing an axplosive charge on the rock, except that technically that isn't the exact same thing as a sound. It is a shock wave. Ordinary sound isn't really quite enough.

[teenagefurball]

Lol not quite what I was looking for

[CraigD]

I assume you're thinking of some sort of practical tool/weapon - something that could be mounted on and powered by a vehicle to tunnel through rock - and that it operate on or near the Earth's surface.

 

How would one go about creating a sound cannon capable of breaking through rock

First, I'd make some rough estimates to decide if it's physically possible. We know from easy-to-picture principles that you can't do any rock-breaking with sound in an airless vacuum, while using sound frequencies transmitted through steel drill bits is a practical industrial drilling technique known as “sonic drilling”. The Earth's sea-level atmosphere has a density greater than a vacuum but less than steel, so some estimating calculations are needed to see if it can be used to transmit enough force to break rocks.

 

Rather than work this out from first principles, I start with a reference stating that the greatest sound pressure that can be transmitted through seal-level air is about 191 dB SPL. 0 dB SPL = 0.00002 N/m², so the greatest pressure that could be produced using sound is about [imath]0.00002 \cdot 10^{19.1} \dot= 2.4 \times 10^{14} \,\mbox{N/m}^2[/imath]

 

A rough estimate for the crush strength of stone is about 5 x 10⁶ N/m², so it looks like there’s no physical limitation of normal atmosphere to crushing stone.

 

Next, I’d reverse the order of the calculations to estimate at what sound intensity a rock tunneling sound cannon would need to produce at the target rock, if all of the sound were absorbed by the rock [imath]10 \log \left(\frac{5 \times 10^6}{0.00002} \right) \dot= 114[/imath], a pretty modest sound level that wouldn’t even hurt your ears. Rock clearly doesn’t absorb sound very well, so this estimate isn’t likely to be very close to the what the sound cannon needs (a good thing, as I’d have demolished my house years ago if it was!), but it helps give a sense of the feasibility of this thing.

 

From this, I can’t see any obvious reason a rock-breaking sound cannon isn’t possible, but suspect it’d be a difficult work of engineering to build a machine that would need huge amounts of power, wouldn’t work as well as centuries old mechanical drills, wouldn’t work from much further away than a drill, and would be dangerous to bystanders. Who'd want such a thing?