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I've recently been replaying Skyrim (for about the fifth time now), and I've stumbled across something I thought would make for an interesting question.

The Greybeards are a group of extremely powerful, isolated mages who live on top of a remote mountain. When visiting them, none (except for one) talk to you, for it's said that they are so trained in the way of the Thu'um that them speaking to you will kill you. (For reference, in Skyrim, there exists something called the Thu'um, which is a shout that can be used to unleash varied powerful effects.) In this case, the Greybeards are so trained in the way of the Thu'um that they cannot even talk to you for the pure energy and force of their voice will kill you.

Could an organism kill its prey (to simplify things, assume this species eats primarily humans) by shouting at it? If so, how? How would this species not kill one another through its death shout?

Unlike this question, I am asking for a solution that would kill an organism, not merely stun it.

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    $\begingroup$ Years of training to control their voices and they can't control their voices enough not to kill? SMH. Makes more sense that they're jerks, really. $\endgroup$ – The Nate Jun 8 '16 at 4:29
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    $\begingroup$ @TheNate The most powerful of the Greybeards can speak to you. As your voice grows in power, you apparently go through a phase when you can't speak to normal people without killing them, but you learn to control your power later. $\endgroup$ – Molag Bal Jun 8 '16 at 5:23
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    $\begingroup$ Of course no one ever thought to just talk sideways... $\endgroup$ – aslum Jun 8 '16 at 12:48
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    $\begingroup$ "JUST DIE, WILL YOU!!!" $\endgroup$ – David Richerby Jun 8 '16 at 15:07
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    $\begingroup$ I take it that the OP has never been married. $\endgroup$ – dotancohen Jun 9 '16 at 14:27
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Yes, but with a big ol' Asterisk

Sperm whales hunt giant squid. How the whales manage to subdue such able prey has been a mystery. One hypothesis, proposed more than 20 years ago, speculated that the whales use powerful ultrasound shrieks to knock the squid senseless before scooping them up. Like bats and dolphins, some whales use ultrasonic clicks to find prey and navigate. The basic premise is, that since sound travels faster underwater, a beam of sound (echolocation) narrow enough could kill in the same way shockwaves do; by rupturing the organs of the animal. Now for the asterisk: this will only work underwater or on a world with a dense atmosphere. Not on land on an earth-like world.

Another (non-biological) example are long range acoustic devices used by the police. In simple terms, it works by using the vibrations of sound at such a low frequency that it becomes one solid beam. This beam simply applies pressure on the diaphragm and makes it difficult to breath. It's the Death Ray we all wanted as children.

A few helpful links of weaponized echolocation that I've found on my travels;

  1. http://www.livescience.com/7297-whales-attack-squid-mystery-deepens.html
  2. http://www.science20.com/squid_day/do_sperm_whales_use_sonar_stun_giant_squid
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    $\begingroup$ Those monsters have a shout that can reach 230 decibels. In comparison rock bands like KISS and Manowar have a hard time going past 130. Nice answer. $\endgroup$ – Renan Jun 8 '16 at 2:47
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    $\begingroup$ Another example: Some mantis shrimp attempt to crush their prey with very powerful claws; according to the linked articule: "Even if the initial strike misses the prey, the resulting shock wave can be enough to stun or kill." $\endgroup$ – kungphu Jun 8 '16 at 6:05
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    $\begingroup$ Now the real question is, how to pack that mega sized whale shout into a land animal to hunt humans. Sperm Whales are like 10x in length and 600x in weight of humans. A sperm whale is ~50 ft and ~45 tons, one of the biggest elephants was 12 tons and stood ~13 ft. tall. I don't see any sea animal having a primary diet of humans. $\endgroup$ – Timmy Jun 8 '16 at 12:20
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    $\begingroup$ Water based creatures aren't going to survive long subsisting on humans. $\endgroup$ – James Jun 8 '16 at 14:33
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    $\begingroup$ @Timmy actually to make this work on land, you would need to quadruple the 230 dB of the whale $\endgroup$ – TrEs-2b Jun 8 '16 at 17:30
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Yes.

If your species could evolve to emit a high-pitched screech at around 180 dB, you're set. According to this Reddit post, a sound of 180 dB would be perfect for this, as past 160 dB, you will stop being able to breathe, and cells in your brain and ears will die. However, there is still a 50% chance that you may survive past this point. After 180 dB, human death is basically guaranteed.

It wouldn't be advisable to do raise that decibel value any further, as any sound past ~190dB is characteristic of large bombs or tornadoes. Keep in mind that the largest bomb used in World War 2 (excepting Hiroshima and Nagasaki) was only 220dB.

As such, now that we've found a perfect range of around 180dB to 190dB, take the lower of the two, as producing a slightly quieter sound saves some energy.


As for not killing its own species, I'd suggest having your species not have ears (at least not external ears). By doing this, your species will only feel the force of the scream, not the actual sound. Also, I'd suggest building a stronger membrane/skull around the brain, so the sound waves need to travel through an extra few layers of thick membrane before they can reach the brain, at which point they will hopefully be mostly nullified.

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    $\begingroup$ Sperm whales can shout at up to 230 decibels. Not as dramatic as "fuz-ro-dah", but much more lethal! $\endgroup$ – Renan Jun 8 '16 at 2:48
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    $\begingroup$ I don't think simply removing ears is enough for not hurting itself. (not to mention it's own species) When we are talking about sound waves that kill, we are not talking about death due to over-stimulation to ear, but sound waves as energy in vibrating air or other medium (e.g. liquid in body). A sound insulating skin is needed, and some protection to breathing system is necessary if they are making that 180dB by shouting. If they are not making the sound by shouting, at least the ability to stop breathing for a while (that while to cause damage to their prey) is needed. $\endgroup$ – cytsunny Jun 8 '16 at 5:56
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    $\begingroup$ 180db is not slightly quieter than 190db, it's an order of magnitude quieter as it's a logarithmic scale. $\endgroup$ – Separatrix Jun 8 '16 at 8:34
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    $\begingroup$ Each 10dB increase is a 10x over the previous value. So a 220dB bomb sound is actually 10,000x (10^4x) as much energy as 180dB. Secondly, we often say decibels to refer to the volume of sound, but it's applicable in a lot of places other than sound. See en.wikipedia.org/wiki/Decibel $\endgroup$ – Martin Carney Jun 8 '16 at 20:29
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    $\begingroup$ Fi, are we accepting Reddit as fact nowadays? $\endgroup$ – James Jun 10 '16 at 18:20
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You should give a look to a kind of shrimp called "Alpheidae". It doesn't really kill by shouting, but produces an underwater noise which power can reach up to 230 dB, if I remind well, killing its prey.

EDIT

Unfortunately I can't find english sources as good as french sources on this specific topic, but you can have a look to this article, detailing the mechanism producing such a loud noise with this shrimp : http://www.todayifoundout.com/index.php/2010/09/a-shrimp-is-one-of-the-loudest-animals-on-the-planet/.

Here is the proof of the beginning of my post :

The snapping shimp has proven to be stiff competition for larger animals like the Sperm Whale (230+ decibels) and Beluga Whale for the title of ‘loudest animal in the sea’. The snap of its claw releases a sound that can reach 218 decibels- louder than a gunshot.

And here is the "answer" to this topic :

The pressure of the snapping bubble is sufficient to stun a passing crab or even kill small fish.

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  • $\begingroup$ Welcome to the site, MedAl. As you may not be aware, the Stack Exchange network of sites is dedicated to detailed answers to questions. As such, would you please collect research concerning this species and include it here by editing your post? Otherwise, this may be deleted as inadequate for an answer. $\endgroup$ – Frostfyre Jun 9 '16 at 3:15
  • $\begingroup$ I disagree that it should be deleted. It does answer the question and provide enough to start with. But it would be much more appreciated if it were expanded. $\endgroup$ – bilbo_pingouin Jun 9 '16 at 5:21
  • $\begingroup$ You are right I have been a bit "careless" here. The answer has been edited. $\endgroup$ – MedAl Jun 9 '16 at 7:08
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    $\begingroup$ Here is a video discribing the cavitation bubble stun/kill attack of the snapping shrimp. Enjoy! youtube.com/watch?v=Zg10Et8FEWc $\endgroup$ – Jim Jul 16 '16 at 3:23
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If you want to make a really exotic creature you could design it to have two mouths that shout at the same time, at the place the sound meets there will be constructive interference if the sounds are of equal frequency and phase and therefor the sound will be amplified. If the mouths are movable this could give the creature great control at what it hurts with its shouth while things that are closer or further away from the prey will be safe. As long as the unamplified sound is safe that is.

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  • $\begingroup$ This doesn't really make sense. Constructive interference of two waves just produces a wave whose amplitude is the sum of their amplitudes. So, yeah, it's twice as loud (i.e. 3dB louder), but that doesn't really change very much. $\endgroup$ – ruakh Jun 10 '16 at 5:08
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    $\begingroup$ @ruakh It wouldn't need to change very much as long as the constructive interference is what pushes it over the limit to being leathal. The point of it is to be able to have precision. $\endgroup$ – Martine Votvik Jun 10 '16 at 20:28
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The physics

The first problem as I see it is that sound is directional only because it is blocked.

What is blocking the sound, making it directional, is often the object emitting the sound.

If the object emitting the sound is an organism of the same stature as the organism which it is supposed to kill. Either both would die, or the emitting organism would die, only harming its opponent. Since the emitting organism is much closer and thus must absorb more of the energy than its opponent.

In Nature

Specific scenarios are of course available to see in nature, but they are always this one animal kills this other type of animal because it is smaller, more sensitive or has another specific flaw which the killer animal has evolved to exploit.

TLDR;

Using sound to kill any other organisms could never be as cost efficient as evolving a claw, teeth, beak or horn.

Using sound to prey on specific organisms can be cost efficient, as we see on our own planet.

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Not really.

Animals don't need to kill other animals to eat them. They need to find a way to make the prey hold still while they ingest them - killing is one of several ways to do that.

Assuming a gradual evolution, a shout will first stun before it becomes strong enough to kill. There is no clear advantage to having a stronger shout, but there are several drawbacks: Stronger shout requires more energy, stronger shout endangers own species, stronger shout requires better protection mechanisms in own species.

Yes

What can happen is that an animal evolves that has a shout that stuns it's prey A. Then a new prey B enters the ecosystem which gets killed by the shout. So the animal evolved to stun prey A, then evolves to switch the diet to prey B. Of course, unless there's some evolutionary pressure to keep the strong stun, natural selection would then favor individuals with a weaker, more energy efficient shout.

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Yes.

Evolution is slow enough and proven through history that a species develops natural protection and survival. Millions of years of acoustical evolution would undoubtedly lead to natural internal defenses.

Thicker cell walls, stronger thicker bone structures, organic structures that are not subject to acoustic stress. I can see it happening pretty easily tho over a very long time.

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Evolution favors those things that increase an organism's chances for reproduction. So for the answer to this question to be true, you have to take into account whether other things evolved to be susceptible to death via sound pressure or sound waves.

For that to be true, you have to have a reason that the other organism is so frail - some advantage that this frailness gives it which makes reproduction more likely.

An organism that dies from moderate to significant sound pressure waves would be at the mercy of our planet's weather system.

So you need to change the weather system, or at least the micro-climate of the area inhabited by these organisms. If you only prepare a particular environment, though, rather than terraforming the whole planet, then you decrease their chances of survival outside that environment, and thus their likelihood of them surviving for centuries.

All this points to possibilities, but it would seem to me that all the possible paths that would justify this would be considered exceptional and highly unlikely.

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Given all the other answers before, I would like to point out that the sound would be simply to hurt their eardrums. Any sound that could FUS-RO-DAH somebody would require an amount of energy that could cause a black hole.

Source: https://www.youtube.com/watch?v=8VGDhGsYoSA

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