Scientists make loudspeakers that can absorb sound for pure silence
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École Polytechnique Fédérale de Lausanne (EPFL) scientists have built a plasma transducer that can reduce noise better than conventional tools through a new concept they call the active “plasmacoustic metalayer.”
This is according to a press release by the institution published last week.
“We wanted to reduce the effect of the membrane as much as possible, since it’s heavy. But what can be as light as air? The air itself,” explained Stanislav Sergeev, a postdoc at EPFL’s Acoustic Group and first author.
“We first ionize the thin layer of air between the electrodes that we call a plasmacoustic metalayer. The same air particles, now electrically charged, can instantaneously respond to external electrical field commands and effectively interact with sound vibrations in the air around the device to cancel them out.”
“As expected, the communication between the electrical control system of the plasma and the acoustic environment is much faster than with a membrane.”
Compact plasma absorber
The plasma has the added benefit that it can be tuned to work at low frequencies as well as high ones and is more compact than most conventional solutions.
“100 percent of the incoming sound intensity is absorbed by the metalayer and nothing is reflected back,” said EPFL’s Acoustic Group’s senior scientist Hervé Lissek.
This results in a compact plasma absorber that can tune out an audible sound frequency of 20 Hz with a plasma layer of only 17 mm thick. Most conventional noise reduction solutions, like absorbing walls, need to be at least 4 m thick, severely limiting feasibility.
“The most fantastic aspect in this concept is that, unlike conventional sound absorbers relying on porous bulk materials or resonant structures, our concept is somehow ethereal. 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” says Hervé Lissek.
Partnerships
Now, EPFL has entered into a partnership with Sonexos SA, a Swiss-based audio technology company, to develop active sound absorbers that use the plasmacoustic metalayer concept. Their products aim to reduce noise in a wide range of applications, including the automotive, consumer, commercial, and industrial sectors.
“This strategic collaboration leverages EPFL's expertise in material science and acoustics, as well as Sonexos' proven track record in delivering high-performance audio solutions,” explained in the statement Mark Donaldson, CEO and Founder of Sonexos.
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