Researchers at École Polytechnique Fédérale de Lausanne (EPFL) have developed a noise reduction technique using an “active plasmacoustic metalayer,” which can be tuned to reduce noise. The technique involves ionising the air between electrodes to create a plasma transducer, which can produce sound without the need for a physical membrane. The membrane in traditional loudspeakers limits the frequency range of operation due to its weight and inertia. The EPFL researchers believe that their new technique could be used to create more efficient and effective active noise reduction systems. The study was published in the journal Nature Communications.
Following a recent study published in the journal ‘Nature Communications’, researchers from the École Polytechnique Fédérale de Lausanne (EPFL) have found a new way to reduce noise by using active ionisation of air.
The researchers built a plasma transducer demonstration to research noise reduction. Plasma transducers work by ionising the air with wires to create an electric field strong enough to ionise the air molecules in a network of parallel wires or a plasma transducer which results in the production of sound. The charged ions are then driven along the magnetic field lines, pushing the remaining non-ionized air in a manner that generates sound.
Although the idea of a plasma loudspeaker is not new, the scientists were intrigued by the idea of using plasma to reduce noise since it gets rid of one of the most important aspects of conventional loudspeakers: the membrane. Loudspeakers equipped with membranes, like the ones in your car or at home, are some of the most studied solutions for active noise reduction. It’s active because the membrane can be controlled to cancel out different sounds, as opposed to a wall that does the job passively.
The problem with using the conventional loudspeaker as a sound absorber is that its membrane limits the frequency range of operation. For sound absorption, the membrane behaves mechanically, vibrating to cancel out the sound waves in the air. The fact that the membrane is relatively heavy, i.e. the inertia of the membrane, limits its ability to interact efficiently with fast-changing sounds or at high frequencies.
“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 plasm-acoustic meta layer. The same air particles, now electrically charged, can instantaneously respond to external stimuli such as music or speech and produce sound waves.”
The EPFL researchers developed a novel idea, which they refer to as the active “plasmacoustic metalayer,” which can be tuned to reduce noise. The study found that by using active ionisation of air, it is possible to reduce noise by up to 50 decibels. The researchers believe that this technology could be used in various applications, including noise reduction in aircraft cabins, reducing traffic noise in cities, and improving the acoustics of concert halls.
The study also found that a loudspeaker can both produce and absorb sound. This means that a plasma transducer could be used not only to produce sound but also to absorb it, making it a useful tool for noise reduction.
The EPFL researchers are now working on developing the technology further, with the aim of creating a plasma transducer that can be used in real-world applications. The researchers believe that this technology has the potential to revolutionise the way we think about noise reduction and could have a significant impact on our daily lives.
To put the last piece of the puzzle in place, the use of active ionisation of air is a novel and exciting way to reduce noise. The EPFL researchers have shown that by using a plasma transducer, it is possible to produce sound without the need for a membrane, which makes it more efficient at high frequencies. This technology has the potential to revolutionise the way we think about noise reduction and could have a significant impact on our daily lives.
