We’ve come a long way since the big, bulky speakers of decades past. Nonetheless, product developers and audiophiles are eager to create speakers (including those of the wearable variety) that are thinner, lighter, and more comfortable to use than anything we’ve seen before. To be worth making and buying, though, these inventions would need to be just as effective as their existing counterparts—including when it comes to active noise cancellation or ANC.
Researchers at École polytechnique fédérale de Lausanne (EPFL) in Switzerland have made a system that combines a lightweight form factor with surprisingly impressive ANC. Rather than comprising what we typically refer to as a speaker today, the prototype consists of an ionized air plasma propulsion system. The result is a device with a narrow footprint and noise-canceling abilities rivaling the heaviest conventional speakers’ ANC abilities—making it possible to silence the noise commonly found in busy rooms, planes, and cars unobtrusively.
Regular speakers use cones to push and pull the surrounding air, resulting in pressure waves that we perceive as sound. (That’s why you feel vibrations when you rest your hand on an active speaker, whether it’s the one on your phone or the one you bust out for big parties.) According to a paper published in Nature Communications, EPFL’s plasma-based speakers instead use electrodes to ionize a thin layer of the surrounding air. This creates a plasma with both positively and negatively charged particles. When these particles are magnetically accelerated, they interact with the air to create pressure waves.
EPFL first leveraged this technology in a prototype in 2020. The loudspeaker, which lacked noise-canceling capabilities, proved effective at producing sound in “stable environments” but performed poorly in spaces with fluctuating acoustics (shown in the video below). This led the team to pursue ANC. Because the ionized air plasma becomes electrically charged, it can react with pressure vibrations—like those produced by other sources, such as road noise or people talking—to neutralize them, creating a noise-canceling effect.
The team’s plasma-based ANC speaker is good at scrubbing out both high and low frequencies, making it effective with treble and bass interference. "One hundred percent of the incoming sound intensity is absorbed by the metalayer and nothing is reflected back," EPFL Acoustic Group senior scientist Hervé Lissek told New Atlas. "We have unveiled a completely new mechanism of sound absorption that can be made as thin and light as possible, opening new frontiers in terms of noise control where space and weight matter, especially at low frequencies."
EPFL quickly licensed the system to Sonexos, a Swiss audio engineering company. The two entities will now work together to develop the technology for commercial use.
