Most of us probably don’t yell every day,
but we are no strangers to hearing yelling. Small children frequently shout at shopping
centers, and we hear loud shouting at rock concerts and sporting events. Over the years, there have even been contests
such as the world screaming competition held in Thailand in 2009. What has not been attempted before is yelling
on a worldwide scale. We will examine some of the possible effects
of this unusual sound experiment in this episode of The Infographics Show, “What would happen
if the whole world yelled at the same time?” Before we begin, we should discuss what sound
is. Sound is a vibration that has pressure and
moves in the form of waves. A 17th century scientist named Robert Boyle
discovered sound cannot pass through a vacuum. It can only travel through a medium such as
air or water. Sound is measured in decibels (dB). The decibel scale is a logarithmic scale,
not a linear one. It is based on the powers of 10. According to one source, “If one sound is
10x times more intense than another sound, then it has a sound level that is 10*x more
decibels than the less intense sound.” The starting point of the decibel scale is
called the threshold of hearing (TOH), which “is the faintest sound that a human ear
can detect.” It is “assigned a sound level of 0 decibels
(abbreviated 0 dB) and “corresponds to an intensity of 1*10-12 W/m2.” Here is a chart of the decibel scale: As you can see from the chart, the sound of
rustling leaves has an intensity level of only 10 dB (not 100dB) even though it is 10
times greater than TOH. The sound of a whisper has an intensity level
of only 20 dB even though it is 100 times greater than TOH. To get an idea about how many decibels of
sound can be created by a large group of people, we looked at the current world record for
the loudest crowd in the world. According to Sports Illustrated, fans of the
Kansas City Chiefs set a new Guinness World Record for the loudest outdoor stadium in
2014 when their noise level peaked at 142.2 decibels. More than 76,000 people were in attendance. Using this data, we were able to come up with
a rough estimate of how many decibels of sound would be created by the population of the
entire world, which is currently about 7.6 billion people. If 1 stadium filled with 76,000 people created
a sound that was 142.2 dB, then 10 stadiums would create a sound that is 152.2 dB. Working our way up to 100,000 stadiums, which
is the equivalent to 7.6 billion people, we find that all the people in the world could
reach a sound level of 192.2 dB. Here are some of the effects that this level
of sound could cause: 1. Ruptured Eardrums Depending on the duration of the sound and
one’s distance from the source of the sound, the whole world yelling at the same time could
cause some potentially serious hearing problems. Various sources indicate that sounds reaching
150 dB or higher can create enough pressure to cause human eardrums to rupture. WebMD notes that this is due to the pressure
tearing a hole in the tympanic membrane, which is located between the outer ear and inner
ear and helps to convert vibrations to sound. Some people do not notice that their eardrum
is ruptured, while others experience various symptoms that include “ear noise or buzzing,”
“facial weakness or dizziness,” or “hearing loss that may be partial or complete in the
affected ear.” In most cases, ruptured eardrums heal on their
own, although it may take several months. Some seriously ruptured eardrums may require
treatment such as surgery. 2. Other Hearing Problems Even with a short amount of exposure, hearing
the whole world yelling at 192.2 dB could lead to other serious hearing problems. One noise reduction website notes that “noise
levels above 140dB are not considered safe for any period of time” and that “at 140
decibels, immediate nerve damage can occur.” According to the American Speech-Language-Hearing
Association, “short, loud noises” can damage delicate hair cells located in the
cochlea, which is the main structure of the ear that is responsible for hearing. These sensitive hair cells help transmit vibrations
into “electrical signals” that your brain translates into sounds, and the hair cells
cannot be fixed once they are damaged. This damage can cause a variety of hearing
problems such as noise-induced hearing loss, ringing in the ears called tinnitus, and an
extreme sensitivity to sound called hyperacusis. Using ear protection would not be enough to
reduce the sound to a safe level. According to one source, “properly fitted
earplugs or muffs reduce noise 15 to 30 dB.” With a noise reduction of 30dB, the sound
would still be high at 162.2 dB. Protection from a combination of earplugs
and earmuffs, which would reduce the sound by an additional 10 to 15 dB, might possibly
prevent eardrum rupture but not the other hearing problems. The sound level would range between 147.2
dB and 167.2 dB. 3. Shattered Glass Theoretically, it is possible for 7.6 billion
people yelling at 192.2 dB to shatter glass but only under certain conditions as outlined
in a Live Science article. First of all, everyone in the world would
have to yell at a frequency or pitch that is the same as the resonant frequency of the
glass, which is the frequency that would cause the glass to vibrate enough to shatter. Second, the glass would have to be made of
a material that is prone to break easily. Thin glasses and glasses with “tiny fractures”
are a good choice. Third, the yell would have to last long enough
to cause enough vibration for the glass to shatter, which one source estimates is “at
least two or three seconds.” There would also have to be some way to concentrate
the voices of 7.6 billion people into a single sound source directly in front of the glass. It is easy for one person to put a glass right
next to his or her mouth before sounding off, but how could 7.6 billion people get that
close to the glass at the same time? 4. Lots of Watts Sound exerts a force that creates energy. According to Physics Central, the “average
human yells at about 80 decibels, which carries along with it about .001 watts of energy . . .” That
seems like a miniscule amount, but when 7.6 billion people yell at the same time, they
produce an impressive 7,600,000 watts of energy. Using data from the Northwest Power and Conservation
Council, we find that’s enough power to keep a traffic signal operating for almost
2 years! The concept of converting sound energy from
yelling into electrical energy is not as far-fetched as you might think. The Daily Mail reports that Thorpe Park Resort
outside of London recently installed “kinetic energy harvesting devices” on all the cars
of its attraction called The Walking Dead: The Ride. These devices will “not only suck up the
energy of screams, but that from g-force and vibrations too.” The energy collected by these devices will
be used to charge cell phones after it is transferred to an “on-site mobile charging
point.” The whole world yelling at the same time will
probably never happen. Gathering 7.6 billion people together in one
area and coordinating them to yell at the same time seem like impossible tasks. And giving the whole world voice lessons so
everyone could reach the right pitch to break glass also does not seem very realistic. However, if it did happen, it would be amazing. What is the loudest event that you ever attended? Let us know in the comments! Also, be sure to check out our other video
called Could the black death happen again?! Thanks for watching, and, as always, don’t
forget to like, share, and subscribe. See you next time!
