Marine Predator That Uses Sound as a Weapon?

Question

Let's say a bunch of crazy scientists develop the ultimate marine predator. How feasible would it to give this whale sized creature a sonic attack that can be a hazard to humans that use small submarines?

Answer 1

And again, the answer is:

Nature beat you to it _(somewhat)

Behold: The Mantis Shrimp

[smasher and spearer strikes] strike by rapidly unfolding and swinging their raptorial claws at the prey, and can inflict serious damage on victims significantly greater in size than themselves. [...]
Even if the initial strike misses the prey, the resulting shock wave can be enough to stun or kill.
[emphasis mine]

While a shock wave is not the same as sonic attack, but they are quite similar. A soundwave is basically a moving medium, while a shock wave is nothing entirely different. In this case:

Because they strike so rapidly, they generate vapor-filled bubbles in the water between the appendage and the striking surface—known as cavitation bubbles. The collapse of these cavitation bubbles produces measurable forces on their prey in addition to the instantaneous forces of 1,500 newtons that are caused by the impact of the appendage against the striking surface [emphasis mine]

The killing weapon is not the sound, but you can't have a shock wave without sound. It is more of a secondary thing, though.

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You want it whale sized. That might be difficult, but I doubt that would make it impossible.
It probably does not even have to be that big.

From how I understand the effect, it only works, because the animal is small and such massive accelerations are possible. (You'd need a lot more force to accelerate a whale-appendage with 10,400g)

So you would be dependend on using this effect many times simultaneously with several organs and not a big one. You could build up massive pressure and damage weak points of the submarine easily.

If you bring intelligence into it, you would not even need that much size. All you have to accomplish is to damage the submarine's moving capabilities and you are done. Then you have basically all the time in the world.

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See also: The Pistol Shrimp

Answer 2

You might not think of it as a sonic attack by the time you're done with it.

First off, there is some prior art. Sperm Whales can click at over 230dB. These are actually powerful enough to vibrate a human body to death (technically, they cause pulmonary edema). So there's something to it.

But submarines change the story.

If your submarines were "scientist grade," they might be damaged by a loud sound wave. If you vibrated the submarine just right, you could cause the materials in the outer shell to fracture, and that would compromise the submarine. However, if your submarines were "military grade," it's going to be harder. The military submarines are designed to withstand the explosion of a torpedo at close range. Such an explosion basically is a sound weapon. It's a shock wave.

Consider the Mark-14. This torpedo was a mainstay of the US military during WWII. It had 643lb of explosives in the front of it. Given that it's the WWII torpedo, we should expect modern vessels to be more resilient against an attack like this. This thing detonated pretty much right against the hull of a ship, so call it 0.5m away.

One of the rules of sound is the inverse-square law. Increase the distance by a factor of $x$, and you affect the power by $\frac{1}{x^2}$. If your creature wants to set off an unfocused sound weapon 100m away, that's 200 times the distance. This means you need 40,000 times the force to create the same result at the target. That's the equivalent of detonating 12,860 tons of explosives. Focusing the sound could decrease that, but probably by a factor of 100 at most. You're still talking hundreds of tons of explosives worth of force.

While you could come up with a creature that could exhibit such extravagant capabilities, it isn't really and effective approach for a predator. They won't have such un-refined tools. They are inefficient from a caloric perspective. The only reason I can think of for a predator to have something like this is if they went after schooling fish, but fish would be stunned with far less power than this. Maybe if you're hunting an entire pod of whales at once?

If I may reference ArtificialSoul's answer (since he posted it while I was typing), what you would likely see is a shock wave generated by an impact. The Mantis Shrimp is an excellent example of this.

After all, punches (and kicks) are sonic weapons, when viewed in slow motion.

Answer 3

Use harmonics.

As other answers have mentioned, having enough sheer power to destroy whole ships at any significant distance is probably out. But if the creatures are skilled enough in the use of their sound projection they may be able to find the natural frequency of some vibration-sensitive component in the ships and rattle that to pieces with significantly less energy.

Rattling critical pieces of the crew is also a theoretical possibility. Infrasound (below the range of human hearing) researchers often report visual and aural hallucinations in response to particular frequency ranges and intensities (usually in the realm of 9Hz if I'm remembering correctly.) There have been some injuries reported from the U.S. Embassy in Cuba that would be consistent with the kinds of damage that could occur with exposure to high-intensity infrasound, but so far nobody has a good explanation of how such a thing could have been done intentionally. Many "haunted" locations have been found to, under certain conditions, naturally produce infrasound of various frequencies and intensities.

Both of these are harassment weapons more than main battle weapons, but it would add tension as the humans keep detecting faint blips on the edge of their sonar range while suffering from inexplicable equipment failures, migraine headaches, and always feeling like they're being watched and seeing things out of their peripheral vision that aren't there when they turn to look.

Addendum: https://en.wikipedia.org/wiki/Sound_from_ultrasound

Thinking about this I remembered an old scientific article about the development of modulated ultrasound. I don't know how differently it works underwater, but ultrasound can be focused much more tightly than lower frequencies and be used as a carrier for lower frequencies to deliver them to particular places. I'm not sure where to find the numbers on how tightly you could focus it underwater, but it might be a way for them to deliver higher intensity bursts more efficiently.