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The Sound So Loud That It Circled the Earth Four Times

nautil.us

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Re: The Sound So Loud That It Circled the Earth Four Times

#21

Post by ars »

josu wrote: post #19
jbert wrote: post #5

Nice. I hadn't thought of there being a limit (due to vacuum) to sound intensity. Reminds me of this recent comment on reddit: http://np.reddit.com/r/space/comments/2h9y9g/the_first_launc... "the Saturn V rocket produced a SWL (Sound Power Level) of about 220 decibels, which is sufficient to melt concrete nearby and set grass aflame a mile away,"

But the article says: "This limit happens to be about 194 decibels for a sound in Earth’s atmosphere." Therefore, wouldn't 220db be like -280°C? EDIT: Somewhat of an answer: 194.09(P) = 1 (ONE) AIR ATMOSPHERE = 14.6962 POUNDS PER SQUARE INCH = 14.6962 P.S.I.= 1 ATM SOUND WAVES DISTORT AND ARE NOW DEFINED AS SHOCK WAVES AND THEY BEGIN TO FOLLOW SHOCK WAVE BEHAVIOR. PARTICLE VELOCITY (BLAST WIND) = 590 FEET / SECOND =…

At that point it's not a sound anymore but rather a shockwave.

Once it dissipates a bit it becomes a sound again.

Re: The Sound So Loud That It Circled the Earth Four Times

#22

Post by marcosdumay »

BrandonMarc wrote: post #15
jbert wrote: post #5

Nice. I hadn't thought of there being a limit (due to vacuum) to sound intensity. Reminds me of this recent comment on reddit: http://np.reddit.com/r/space/comments/2h9y9g/the_first_launc... "the Saturn V rocket produced a SWL (Sound Power Level) of about 220 decibels, which is sufficient to melt concrete nearby and set grass aflame a mile away,"

Wait, the sound caused the grass to catch fire?!

A 220 dB sound is quite strong.

As an example, its intensity (in W/solid angle) is 14 orders of magnitude (AKA 100 billion times) highter than the 80 dB people usualy use as a safety limit.

Re: The Sound So Loud That It Circled the Earth Four Times

#23

Post by beloch »

To put this in context, the Krakatoa eruption released energy roughly equivalent to a 200 megaton bomb, which is roughly four times larger than the "Tsar Bomba", an H-Bomb which is the largest nuclear weapon detonated to date. The globe's average temperature fell 1.2 C after the eruption due to SO2 increasing the Earth's albedo. The Volcanic Explosivity Index (VEI) of the Krakatoa eruption was 6, and it's estimated to be a roughly once in a century eruption.

When you think about it, we're living on a extremely thin crust that's formed on the surface of a molten, roiling ball of rock and metal. People are strangely obsessed with the threat of asteroid impacts when what's beneath our feet presents a perhaps even greater danger, one which we know next to nothing about!

Re: The Sound So Loud That It Circled the Earth Four Times

#24

Post by stromgo »

aatish wrote: post #12
danielweber wrote: post #11

So the sound got harder to hear as you were farther away, but what if you were at the exact antipode on Earth? Would it have been audible at all?

The sound was only audible up to 3000 miles in radius, or about 1/13th the globe. It wasn't audible in the other side of the Earth (although it was detectable.)

He mentioned the "exact antipode on Earth", so he's probably thinking of an effect similar to antipodal chaotic terrain [1]. The fact that sound was only audible up to 3000 miles in radius is not enough to rule it out, you need other arguments.

[1] http://en.wikipedia.org/wiki/Caloris_Basin#Antipodal_chaotic... ("It is thought by some to have been created as seismic waves from the impact converged on the opposite side of the planet.")

Re: The Sound So Loud That It Circled the Earth Four Times

#25

Post by b_emery »

vanderZwan wrote: post #13
aatish wrote: post #3

Hey, I'm the author of the post (on twitter @aatishb). Thanks for voting it up. Would love to hear your thoughts and constructive feedback. Cheers. (PS the references linked to at the bottom of the post are packed with fascinating information about Krakatoa, for anyone who wants to dig deeper.)

It's a great article - makes me wonder how long the shockwave of the impact that killed the dinosaurs must have been echoing across the globe, or the one that created the moon (well, that one was before earth had an atmosphere, but it probably was strong enough to make the entire planet vibrate for quite a while).

> impact that killed the dinosaurs

I once saw a talk about this at a scientific meeting, so the papers are out there. All I can remember from it is that they estimated the ejecta at "about the mass of the Sierra Nevada". This was quite a while ago so I'm sure they've got a better estimate by now.

Re: The Sound So Loud That It Circled the Earth Four Times

#26

Post by SeanDav »

Another amazing/frightening statistic is that pyroclastic flows killed people living 30 miles away over open ocean. If I was living that far away across an ocean, I would have felt perfectly safe. It just boggles my mind that even at this distance Krakatoa was deadly.

Re: The Sound So Loud That It Circled the Earth Four Times

#27

Post by Balgair »

beloch wrote: post #23

To put this in context, the Krakatoa eruption released energy roughly equivalent to a 200 megaton bomb, which is roughly four times larger than the "Tsar Bomba", an H-Bomb which is the largest nuclear weapon detonated to date. The globe's average temperature fell 1.2 C after the eruption due to SO2 increasing the Earth's albedo. The Volcanic Explosivity Index (VEI) of the Krakatoa eruption was 6, and it's estimated t…

My wife is a geo-chemist. She says that plastic is a better term to get an idea on the mantel. Yeah, it is a liquid, but the pressures and temperatures are just so crazy to us that calling it 'roiling' is a little bit of a misnomer. Also, because of these pressures and temperatures, it's hard to ever know anything about the interior of the planet. Turns out, dense things that are very deep and hot are very hard to study.

Re: The Sound So Loud That It Circled the Earth Four Times

#28

Post by dandelany »

jbert wrote: post #5

Nice. I hadn't thought of there being a limit (due to vacuum) to sound intensity. Reminds me of this recent comment on reddit: http://np.reddit.com/r/space/comments/2h9y9g/the_first_launc... "the Saturn V rocket produced a SWL (Sound Power Level) of about 220 decibels, which is sufficient to melt concrete nearby and set grass aflame a mile away,"

Yes! My favorite example of this is the sound made by the space shuttle's solid rocket boosters at liftoff. Techies who have seen recordings of shuttle launches generally assume the guttural crackling, popping roar sound they hear is due to a badly adjusted microphone clipping the loud sounds. In fact, this was a physical phenomenon that could be heard in real life, due to the pressure waves physically "clipping" against a vacuum upon reaching the atmospheric pressure limit! Sorry I can't seem to find any better sources, but this is an anecdote I've heard from several witnesses: http://forums.prosoundweb.com/index.php?topic=98023.25;wap2

Here's a good example of the sound I'm talking about: https://www.youtube.com/watch?v=OnoNITE-CLc&t=1m44s

Re: The Sound So Loud That It Circled the Earth Four Times

#29

Post by SEJeff »

fl0wenol wrote: post #16
SEJeff wrote: post #14

Earlier quoted context omitted.

One thing I'm surprised you didn't mention is infrasound[1], which is sound so low that it can potentially damage the human body. Some of the newer non-lethal weapons the US military use for crowd control include a directional infrasound "gun" that basically vibrates your inner organs fast enough to make everyone super nauseous. [1] http://en.wikipedia.org/wiki/Infrasound

Infrasound is about a specific frequency range of sound which isn't audible but still carries energy (which is why it can be dangerous). This article was about a wideband sound that was so loud that it defies comparison. Loudness is related to the amplitude, or "height" of the wave, not frequency.

Oh agreed, the article just goes into so much detail about sound. Seemed relevant (in my head).

Re: The Sound So Loud That It Circled the Earth Four Times

#30

Post by qq66 »

kordless wrote: post #9
double0jimb0 wrote: post #6

Earlier quoted context omitted.

How does something like the Tzar bomb compare in terms of sound pressure? Would the immense volume of ejected material from the volcanic explosion move more air than a nuclear explosion? I'd guess lots of mass (air molecules) is just vaporized in a nuclear explosion, leaving much less mass to create pressure deltas.

Wikipedia says it was four times as powerful as Tzar Bomba, which would put it in the neighborhood of 200Mt. Technically Tzar Bomba was suppose to yield about 100Mt, but the scientists dialed it down a bit because they were worried about it.

Kind of crazy to think that humans made a bomb 1/4 as powerful as the Krakatoa eruption.
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