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  • [MUSIC]

  • If I had a machine that allowed me to suddenlytransport myself elsewhere, the air filling

  • the vacuum where I used to be would collapse with enough force it would burst the eardrums

  • and cause nausea in anyone standing nearby.

  • Teleportation may sound like a cool idea, but thanks to sound itself, it's a pretty dangerous proposition.

  • [MUSIC]

  • A sound wave is mechanical, it needs a medium to travel through.

  • Right now, the wave created by my voice is wiggling the air back and forth, creating

  • areas of higher and lower pressure.

  • When we talk about how loud a sound is, were really talking about the intensity of that

  • pressure wave. The louder the sound, the more intense the wave.

  • Unlike ripples on a pond, sound moves out from its source in the shape of a sphere.

  • Just like a bubble gets thinner as it gets bigger, the farther we are from the source

  • of a sound, the less pressure there is on a given area of the sound sphere.

  • This means that if we move twice as far from a sound, it will be at one-fourth the intensity.

  • The smallest sound pressure wave we can hear vibrates our eardrum less than the width of

  • a single oxygen molecule! Yet we can comfortably hear sounds a billion times more intense.

  • Hearing has the widest range of any of our senses, by far, so we need a wide scale to

  • measure it. To do that we use decibels.

  • dBs are logarithmic. Something 10 decibels louder is ten times as intense. 30 decibels?

  • A thousand times as intense. Our threshold for pain comes at sounds 10

  • trillion times more intense than the quietest sound we can hear.

  • Highway traffic is about 90 decibels.

  • [gunshots]

  • [jet noise]

  • In 1883, the island of Krakatoa in the South Pacific erupted, sending ash nearly 17 miles

  • into the atmosphere, with a force four times more powerful than the Tsar Bomba, the most

  • powerful nuclear weapon ever detonated. At nearly 180 dB, this explosion shattered

  • eardrums 40 miles away, and pushed a wave of air around the globe four times.

  • Imagine hearing thisBANG! only three thousand miles away. Get close

  • enough to that, and it'll be the last sound you never hear.

  • But there’s an upper limit to how loud a sound can be, and, hint: It’s not “11”.

  • Sound waves push air together at their peak, and leave low pressure in the valleys. Once

  • this part reaches a vacuum, the sound can’t get any louder. Push the wave any harder than

  • 194 dB, then it distorts, heats up, it’s moving faster than the speed of sound.

  • We can go higher, only then it's stopped being sound and has become a shock wave.

  • NASA’s Saturn V rocket was capable of shooting out 7.5 million pounds of space-fire thrust

  • at 200-220 dB. That’s enough pressure to ignite grass a kilometer and a half away and

  • kill everything within a few hundred meters.

  • For Space Shuttle launches, NASA dumped water at a rate of 900,000 gallons per minute into

  • a pool underneath the launch pad to keep the sound waves from literally ripping the shuttle

  • apart.

  • Of course, planets with more dense atmospheres, like Venus or Saturn, could sustain more intense

  • sound waves, and even higher decibel levels.

  • It makes me wonder, what would a lightning storm on Saturn sound like?

  • In fact, I’d like to find out.

  • Stay curious!

  • BANG! [ringing sound]



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B1 中級

一番音が大きいのは? (What's The Loudest Possible Sound?)

  • 376 20
    kinkwanhappy に公開 2021 年 01 月 14 日