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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

#101

Post by abdulhaq »

astrodust wrote: post #96
marcosdumay wrote: post #22

Earlier quoted context omitted.

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.

Saying "quite strong" here is like saying a thermonuclear explosion is "warm". Sound that loud wouldn't just kill you, it'd rip you apart.

I think this is a US/UK English thing, in the US 'quite' only means 'very' whereas in the UK it often means 'a bit'. (I'm guessing your from the UK).

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

#102

Post by saidajigumi »

disillusioned wrote: post #58
dandelany wrote: post #28

Earlier quoted context omitted.

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" aga…

I had the privilege of watching STS-134 launch from the press site and everyone tells you: "it's loud. louder than loud. you will be surprised by how loud it was." and that still wasn't enough to prepare me. It is loud. It is literally like the sound is clipping, the brapping noise moves through your teeth, it vibrates your clothes, you feel it inside of you. It is incredible, and I was so lucky to have watched it fr…

Yesss! I got to see STS-3 (!!!) from the press site. I was just a kid at the time on a school field trip. Our bus was misdirected to the VIP/press site, and they let us stay.. ;-) IIRC, several of the huge rental-only Canon telephoto lenses were in attendance on the photog's hill. The photographers were incredibly cool, talking with us, letting us look through their spotting telescopes and such.

The launch was far and away the loudest phenomenon I've ever heard, or ever hope to hear. Impossible to adequately describe. You don't hear the sound, you are the sound. The universe transforms, and is made of nothing but sound and vibration.

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

#103

Post by EGreg »

jonsen wrote: post #100
EGreg wrote: post #99

Earlier quoted context omitted.

This supports even more that the remaining energy is on the order of X/r^2 and attenuated with the SQUARE of the distance traveled around the globe.

The /r^2 factor is due to the fact that the surface of a sphere grows proportional to r^2. That will hold for the wavefront half way around the earth, but from there it will be reverse. The energy will converge to full strength at the point opposite from the origin. That is if there were no loss. A significant portion of the energy is converted to heat and otherwise dispersed from being a compact wavefront.

The energy is dispersed in all directions through air molecules. At the top it dissipates and at the bottom it is absorbed by the earth. The only extra boost you'd get along vectors parallel to the surface would be reflections of the energy, which other commenters have said is small ... so this term doesn't change enough to get the function out of O(r^-2) does it?

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

#104

Post by dustyleary »

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,"

I almost commented on the reddit post at the time, but decided not to. Now that I see it repeated, I want to.

This is a reading comprehension error, I think. I guess I'm not 100% sure. That "melting concrete and setting grass aflame" comes from the link, here: http://www.makeitlouder.com/Decibel%20Level%20Chart.txt

That link has many decibel levels, and examples, and factoids about the things producing the sound, unrelated to the sound itself.

I think the chart intends to say that the rocket melts concrete, sets grass on fire 1 mile away, and produces sound that is 220 decibels. Not that the sound itself is melting concrete or setting grass on fire.

The reddit post mentions "At 2 kilometers (140+ db), ..."

2km is a little more than 1 mile. So if the sound alone could set grass aflame a mile away, then that would mean that 140db at distance zero is enough set grass on fire.

If it can set grass on fire, then it can set a lot of other things on fire. Paper, clothing, hair, etc...

Some extremely loud rock concerts hit 150db.

So, while I guess I'm not 100% sure that this is an error, I just doubt that rock concert speakers can/would output enough volume to set things right next to them on fire. There would be huge safety issues, and risk of the speakers destroying themselves and other equipment.

I know nobody is right next to speakers this loud, but still... I doubt the accuracy of this 'melting concrete and setting grass aflame via sound' factoid.

I would love to be shown wrong, because it is really interesting if it's true.

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

#105

Post by jonsen »

EGreg wrote: post #103
jonsen wrote: post #100

Earlier quoted context omitted.

The /r^2 factor is due to the fact that the surface of a sphere grows proportional to r^2. That will hold for the wavefront half way around the earth, but from there it will be reverse. The energy will converge to full strength at the point opposite from the origin. That is if there were no loss. A significant portion of the energy is converted to heat and otherwise dispersed from being a compact wavefront.

The energy is dispersed in all directions through air molecules. At the top it dissipates and at the bottom it is absorbed by the earth. The only extra boost you'd get along vectors parallel to the surface would be reflections of the energy, which other commenters have said is small ... so this term doesn't change enough to get the function out of O(r^-2) does it?

You do get a boost from the wave contracting and converging towards the opposite point from halfway around the earth. I think it is not at all obvious what the order of damping will be.

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

#106

Post by EGreg »

jonsen wrote: post #105
EGreg wrote: post #103

Earlier quoted context omitted.

The energy is dispersed in all directions through air molecules. At the top it dissipates and at the bottom it is absorbed by the earth. The only extra boost you'd get along vectors parallel to the surface would be reflections of the energy, which other commenters have said is small ... so this term doesn't change enough to get the function out of O(r^-2) does it?

You do get a boost from the wave contracting and converging towards the opposite point from halfway around the earth. I think it is not at all obvious what the order of damping will be.

Can you back it up with some overview of the math?

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

#107

Post by astrodust »

abdulhaq wrote: post #101
astrodust wrote: post #96

Earlier quoted context omitted.

Saying "quite strong" here is like saying a thermonuclear explosion is "warm". Sound that loud wouldn't just kill you, it'd rip you apart.

I think this is a US/UK English thing, in the US 'quite' only means 'very' whereas in the UK it often means 'a bit'. (I'm guessing your from the UK).

Canadian, which does have a lot of British influence.

Saying a burrito is "quite spicy" usually means "surprisingly" but not "excessively" or "extraordinarily".

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

#108

Post by marcosdumay »

astrodust wrote: post #107
abdulhaq wrote: post #101

Earlier quoted context omitted.

I think this is a US/UK English thing, in the US 'quite' only means 'very' whereas in the UK it often means 'a bit'. (I'm guessing your from the UK).

Canadian, which does have a lot of British influence. Saying a burrito is "quite spicy" usually means "surprisingly" but not "excessively" or "extraordinarily".

I'm Brazilian.

Those things are already too subtle and hard enough to learn in a second language. People defining the same expression with widely conflicting meanings in different places do literally turn it into a maze :)

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

#109

Post by merrua »

marcosdumay wrote: post #108
astrodust wrote: post #107

Earlier quoted context omitted.

Canadian, which does have a lot of British influence. Saying a burrito is "quite spicy" usually means "surprisingly" but not "excessively" or "extraordinarily".

I'm Brazilian. Those things are already too subtle and hard enough to learn in a second language. People defining the same expression with widely conflicting meanings in different places do literally turn it into a maze :)

It should mean, you can't get it wrong, but instead it tends you mean, you are always wrong. Ah well.

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

#110

Post by techdragon »

Toenex wrote: post #86
post_break wrote: post #44

Earlier quoted context omitted.

Standing next to the thing makes you feel like an ant. I visit it once and a while and I just think to myself "we did this, this thing blasted off of the face of the earth with humans at the top"

This quote from John Glenn always reminds me just how brave those sons of bitches were; "As I hurtled through space, one thought kept crossing my mind - every part of this rocket was supplied by the lowest bidder."

I cannot believe I have never heard this quote before. I literally LOLed.
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