[MUSIC] If I had a machine that allowed me to suddenly…
transport 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, we’re
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 this… BANG!
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]
