A new noise-cancelling system being developed in Germany could help to minimize what has become a major source of concern for residents near wind farms. While some noise-dampening systems are already used in turbines, they are “passive”, meaning that they reduce certain frequencies or sources of vibration noise, but do not respond “actively” to the changing frequency ranges of an operating turbine.

The new system “listens” for vibrations and then produces vibrations that exactly match, in reverse, the problematic motion within a turbine tower or base. From PhysOrg:

“These systems react autonomously to any change in frequency and damp the noise – regardless of how fast the wind generator is turning,” says André Illgen of the Fraunhofer Institute for Machine Tools and Forming Technology IWU in Dresden. The key components of this system are piezo actuators. These devices convert electric current into mechanical motion and generate “negative vibrations”, or a kind of anti-noise that precisely counteracts the vibrations of the wind turbine and cancels them out. The piezo actuators are mounted on the gearbox bearings that connect the gearbox to the pylon. But how do these piezo actuators adjust themselves to the respective noise frequencies? “We have integrated sensors into the system. They constantly measure the vibrations arising in the gearbox, and pass on the results to the actuator control system,” says Illgen. The researchers have already developed a working model of the active vibration dampers, and their next step will be to perform field trials.