Plasma Arc Speakers

In science fiction, plasma-based technology is often included because it is perceived as futuristic and exotic. Referring to plasma as exotic is understandable, but the technology behind its creation is less so. Since the invention of electric circuits, it has been possible to easily create and control plasma using high voltages. It is pretty common knowledge that high voltages ionize the air producing plasma arcs. What is not-so-common knowledge is the fact that these arcs of plasma can be used to play music.

Plasma globes are a well known example of plasma.

Anyone who has been in a thunderstorm knows that plasma can be very loud. Lightning strikes can be easily loud enough hear from miles away, or shake your house if it strikes up close. The loud shockwave generated by lightning is caused from the rapid expansion of hot gas transforming into ionized plasma. On a smaller scale the same effect can be reproduced using a flyback transformer circuit. By controlling the frequency of the arc’s shockwave it is possible to accurately reproduce music. The video below is an example of such a circuit.

 

In the video, the fidelity of the arc speaker is quite surprising. In fact, arc speakers are superior for accurate sound reproduction when compared to regular speakers. Conventional speakers generate sound by vibrating a conical structure connected to a magnet. The inertia of the cone resists these vibrations to some degree. This means, by the nature of their design, regular speakers have trouble reproducing some sounds without distorting. Plasma arc speakers on the other hand do not suffer from such a draw back.

 

This leads to an interesting question — if plasma speakers are simple to build and sound better, why aren’t they more common? The truth is there are some major limitations holding the technology back. First off plasma speakers need high voltages to operate. This is potentially dangerous and eats up a lot of energy. Furthermore to increase the volume of a plasma speaker the arc needs to be longer, requiring even higher voltages. This is why large lightning bolts are so loud. On top of being a power hog and posing an electrical hazard, plasma arc speakers also generate ozone. Although ozone is beneficial for mending the ozone hole in our atmosphere, in high enough concentrations the gas is poisonous. Bearing these facts in mind, it makes sense why plasma speakers have not caught on.

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