Reduction of Gearbox Tonalities with the ADD.Sound® Active Vibration Damping Device

The good news first: Wind turbines are becoming more and more powerful. However, the higher performance often also entails a challenge: Increasing tonal sound. And thus, a higher risk for noise-reduced operation and yield losses.

The challenge: New wind turbines = More tonalities?!

Tonal sound is not a new problem, but it is an increasing challenge. This is because the new, more powerful WT types and models often cause more tonalities. Among other things, this can be attributed to the following further developments:


  • Optimized powertrain: Higher power density and more gear stages
  • Improved aerodynamics: Reduced masking due to optimized rotor blades
  • Larger operating range: Operation even at low and high wind speeds
  • Larger rotor diameters & higher towers: Large radiation surfaces

Background: Why do we actually mind tonalities?

Vibrations in the gearbox of a wind turbine can cause tonalities – i.e. noise with a fixed frequency, e.g. humming noise. These are particularly unpleasant for people and thus have to be specifically considered in the evaluation of noise emissions.

The legal standards therefore require a penalty for tonal sound. Where necessary, the wind turbine concerned may no longer be operated in the noticeable operating range. In noise-reduced mode, the corresponding speed ranges can be bypassed, but this entails considerable yield losses.

The solution: ADD.Sound for high performance tonality mitigation over the entire frequency range

Fortunately, we have another piece of good news: Our ADD.Sound active damping device reduces tonalities over the entire frequency range.

The system uses sensors to detect the operating vibration. Using a speed-adaptive control algorithm, it generates active forces that are equal in frequency and amplitude but opposite in phase, thus counteracting the tonal excitation forces in the gearbox. With the help of these precisely induced counter-vibrations, the tonalities are compensated over the entire speed range – directly where they arise.

By moving the black dots you can calculate your individual payback period with our interactive tool:

Amortisation after


not possible

Noise-reduced operation of your WTG can massively reduce the yield of your wind farm. With ADD.Sound you minimize tonality and can return to the normal operation mode. This calculation includes all costs including installation.

Active vibration reduction: Broad range of applications and high mitigation potential (especially compared to passive dampers)

With ADD.Sound, we have a real success story to tell, because...

... the system is not only highly efficient on paper, ...

Reduction of tonality
by up to 10-15 dB

5,000 N damping
force per actuator

... it has also proven itself in in the field.

6 customers,
including 4 OEMS

2,500+ delivered

15+ equipped WT types – with and without gearbox

Successful mitigation of tonalities radiated by tower and blades: What makes us the technology leader in active damping solutions

  • High force scalability due to multiple actuators
  • High damping force at small moving mass
  • Flexible positioning due to modular concept and low space requirement
  • Retrofit possible
  • Broadband compensation over the entire operating range (variability of frequency (RPM) without hardware tuning)
  • Simultaneous compensation of multiple vibration orders (Single or synchronous damping of 1st and 2nd gear mesh / excitation frequency)
  • Damping of all gearbox or hub modes (rolling, yaw, pitch, torsion, …)

From the occurrence of tonalities to the solution: We support you at every step

Please contact us personally


We will be happy to support you with any questions regarding the efficient reduction of tonalities as well as our active vibration damper ADD.Sound.

Timo Klaas

+49 40 524715-265
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Dipl.-Ing. Bernd Wölfel

Lorena Sproll-Astorquiza

+49 931 49708-761
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