Now how

How do monsters get energy from the sound of children’s screams?

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It’s common for children to believe that the creaks in their houses and the howling of wind at night are actually monsters hiding under their beds or in their closets, waiting to jump out and scare them. In Pixar’s Monsters, Inc. and Monsters University, though, this idea is taken literally and the story of monsters is retold, but from the monsters’ point of view. Here, the reason why monsters jump out and scare children is because the monsters need to collect the children’s screams for energy to power the monster city of Monstropolis.

I never encountered Sully or Mike Wazowski in my childhood (probably all for the best), but this means that I was never able to ask what exactly the mechanism for scream energy is.

The idea of having energy produced by sound, though, is one that may have some sound scientific basis.

Why?

With energy such a critical resource, we’re constantly investigating and inventing new means of harnessing energy from the world around us, whether by the sun, wind, or water. As scientists have probably discovered, though, scream energy is one that we can rule out as a viable option for our near future.

How?

Sound doesn’t just appear; it takes the form of a pressure wave. When an object vibrates, it makes a disturbance in the medium it’s in, for example the air. This disturbance is then carried through the air in the form of oscillating pressure waves until these waves reach our ears (Villanueva).

monster4The two determinants of the quality of a sound are frequency and amplitude. If an object is vibrating quickly, it has a higher frequency and shorter wavelength. As a result, the sound is more high-pitched. On the other hand (or claw), if it is vibrating more slowly, the wave has a lower frequency and longer wavelength, emitting a more low-pitched sound. This quality is measured in units of Hertz, with more Hertz indicating higher pitches.

If the sound wave is larger in height, it has greater amplitude and therefore a louder sound. If the sound wave is smaller in height, it has lower amplitude and a quieter sound. This quality is measured in Decibels, which provides quantitative values for how the human ear perceives sound.

Sound carries energy because it can do work (defined as causing change), exerting pressure on the medium it travels through and causing compressions and rarefactions in it. All the energy produced by sound is mechanical energy because there is no chemical change in the wave, and the wave is not contained in discrete particles of energy (“What Is Sound Energy?”).

Scientists have long since developed techniques to convert mechanical energy into electrical energy (electricity). From these mechanisms, we can generate energy from wind or water flow. The most common way of producing energy from water is by building a dam on a river to store water in a reservoir. When water is released from the reservoir, it spins a turbine, which then activates a generator to produce electricity. Other hydroelectric power plants may simply use a small canal to channel river water through a turbine (“Hydropower”). In this manner, the kinetic energy of the moving water is converted into electricity.

Unlike water though, sound produces movement on a much smaller scale than a massive, flowing river. The energy generated by sound is so small that scientists prefer to measure it in terms of pressure and intensity (Pascals and Decibels) rather than the traditional energy measurement of Joules.

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So?

Two Korean researchers have been looking into technology that can convert the sound of our speech into electricity to power our cell phones. It still has a long way to go, though. A normal conversation produces sound at about 60-70 Decibels. Although a cell phone operates using only a few volts, the researchers’ best results have only been able to produce 50 millivolts with sound waves reaching 100 decibels (about the loudness of a car horn) (Cattermole).

So unfortunately, whatever technology monsters have invented to convert the sound of screams into powerful amounts of energy seems to be beyond our reach for now.  If you catch a monster in your closet, though, maybe you can learn some further details!

Written by Constance Kaita 

Works Referenced 

Cattermole, Tannith. “Mobile phones charged by the power of speech.” Gizmag.com. 20 September 2010. Web. 19 July 2013.

“Hydropower.” RenewableEnergyWorld.com. n.d. Web. 19 July 2013.

“What Is Sound Energy?” wiseGEEK.org. n.d. Web. 19 July 2013.

Villanueva, John Carl. “What Is Sound?” UniverseToday.com. 30 March 2010. Web. 19 July 2013.

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