• When does wind make all the right noises?

Reduction of gearbox tonalities with active or passive damping devices

Vibrations in the gearbox of a wind turbine can cause tonalities (noise with a fixed frequency, e.g. whistling noise). These tonalities are particularly unpleasant for people and thus they have to be specifically considered in the evaluation of noise emissions. In accordance with legal standards, surcharges are therefore assigned to the determined broadband sound power level for tonal components. With this surcharge, the authorized limits for noise emissions or the contractually agreed noise levels may be exceeded.

Therefore tonalities have to be reduced. In the wind energy sector, Wölfel has many years of experience in the application of active and passive absorbers which compensate the vibrations at their source before they can spread. This is achieved by precisely applied counter-vibrations.

Active cancellation of tonalities with ADD.Sound

Solution for mastering tonalities with variable frequency: Active damping device – ADD.Sound®


With more than 800 systems in the market, we are proud to be the technology leader in the field of active damping devices for the reduction of gearbox tonalities


  • Compensation of several orders of tonal gearbox vibrations at variable speed (over the entire speed range of the wind turbine)
  • One active absorber ADD.Sound® each is mounted on the torque supports (can also be retrofitted; small installation space required)
  • A compact control cabinet is installed in the nacelle
  • Due to the speed-adaptive control algorithm, ADD.Sound® generates active forces which eliminate the tonal excitation forces in the gearbox
  • Tonal sound is cancelled over the entire range of speed (broadband effect, simultaneous compensation of several tonalities).
Damping devices at the gearbox prevent sound propagation and emission

Solution for mastering tonalities with fixed frequency: Passive damper – TMD.Sound

  • Compensation of one order of tonal gearbox vibrations at one fixed speed (mostly the rated speed of the wind turbine)
  • One passive absorber TMD.Sound each is mounted on the torque supports (can also be retrofitted)
  • TMD.Sound is exactly adjusted to the tonality frequency at rated speed
  • TMD.Sound applies a force that is exactly opposite to the excitation
  • Tonal sound at rated speed is cancelled – no energy supply is required.