Actively reducing noise by ionizing air

Plasma can be used to reduce noise. Credit: EPFL /LTS2 Scientists show that a thin layer of plasma, created by ionizing air, could be promising as an active sound absorber, with applications in noise control and room acoustics. Did you know that wires can be used to ionize air to make a loudspeaker? Simply put, it's possible to generate sound by creating an electric field in a set of parallel wires, aka a plasma transducer, strong enough to ionize the air particles. The charged ions are then accelerated along the magnetic field lines, pushing the residual non-ionized air in a way to produce sound. If a loudspeaker can generate sound, it can also absorb it. While this plasma loudspeaker concept is not new, scientists went ahead and built a demonstration of the plasma transducer , with the aim to study noise reduction. They came up with a new concept, what they call the active "plasmacoustic metalayer" that can be controlled to cancel out noise.