Sound emission measurements and measurements for acceptance tests acording to IEC 61400-11 and FGW guideline, systems for the reduction of gearbox tonalities and for sound source localization with the acoustic camera

Wind turbines generate sound and thus emit acoustic noise. In the course of the turnaround in energy policy, new locations for wind turbines have to be found and there is a huge potential for conflict due to noise pollution.

We offer services and product solutions covering the entire wind turbine approval procedure, from noise impact prediction in the planning phase to acceptance measurement following the commissioning of a wind turbine.

Sound emission measurements and measurements for acceptance tests according to IEC 61400-11

  • As part of the approval of your wind park under immission control law, you want to verify the compliance with sound power levels and document their correct determination?
  • The newly developed prototype of your wind turbine requires the measurement of acoustic emissions as a basis for the type certification?

As a member of the Fördergesellschaft Windenergie (FGW e.V.) (Society for the Promotion of Wind Energy) we perform measurements of emitted acoustic noise and measurements for acceptance tests according to IEC 61400-11 and FGW guidelines. Sound immission control particularly deals with questions of noise propagation outdoors. The objective is to ensure compliance with limit values (Technical Instructions on Noise Abatement) in order to protect the people in the vicinity.

The central success factor for sound emission measurements is a fast reaction time under favorable wind and weather conditions. With branches in Höchberg near Würzburg, Hamburg and Berlin, we can carry out measurements flexibly and efficiently in both southern and northern Germany.

The efficiency of our measurements has also significantly increased with our wireless measuring system RoBin (link to Tab): The time from our arrival at the wind turbine to the start of the measurement is only about 30 minutes due to the simple setup. For example, several wind turbines and several operating modes can be measured in accordance with standards on one measuring day.

Sound Source Localization with the Acoustic Camera Noise Inspector

  • You want to know exactly which parts of the wind turbine increase the noise level or cause tonalities? You also want to know how these tonalities can be eliminated?

In order to be able to plan and initiate noise abatement measures, it is necessary to know the exact source of the noise. We have various measuring systems to cover almost all cases. The acoustic camera Noise Inspector locates sound sources and displays the results as an acoustic photo or video.

We support you when you are confronted with acoustic issues – whether you just have to locate a sound source or want to develop noise abatement measures.

Our references in the area of sound source location (extract):

  • Rhein Energie AG
  • GE Wind Energy GmbH
  • Enercon
  • Vensys Energy AG
  • MAC Energysystems GmbH & Co. KG

RoBin – System for the measurement of sound emissions of wind turbines

RoBin is our wireless measuring system for the standard-compliant sound emission measurement of wind turbines according to IEC 61400-11 Edition 3 / FGW guideline TR1. Due to the simple setup the time from our arrival at the wind turbine to the start of the measurement is only about 30 minutes. Therefore, several wind turbines and several operating modes can be measured in accordance with the given standards in just one measuring day.

  • Convenient: wireless data transfer
  • Compact: components and accessories in handy transport cases
  • Flexible: various interfaces for data acquisition
  • Calibratable
  • Exact: remote control to tag disturbing noise
  • Cost-effective: only one person required on site

The main component of RoBin, the wireless one-man measurement system, is a sound level meter, which detects noise by means of a double-shielded external microphone. A flexibly applicable data logger with six freely configurable analog inputs, one USB and one fieldbus connection registers the operating parameters of the wind turbine. Meteorological data is recorded by meteorological sensors with the required class of accuracy.

Data transfer and electrical power supply are realized using WiFi or lithium battery technology. A radio remote control tags the measurement status (operating and background noise) and marks disturbing noise. Wind bin administration is done automatically in real time. You can comfortably monitor the measurement via tablet PC.

Our sound analysis software, RoBin.Post that has specifically been developed to assume wind power tasks is used to evaluate the data required for sound power calculation. In RoBin.Post, the user can edit data directly recorded with RoBin or any other measured data. Data is evaluated according to latest standards, such as IEC 61400-11and FGW TR1(editions 2.1 and 3), simply by pushing a button. Immediately after the measurement, reports are output automatically which makes the process all the more efficient.

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 sound power level of the wind turbine. 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 with precisely applied counter-vibrations.

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.Soundyou minimize tonality and can return to the normal operation mode. This calculation includes all costs including installation.


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.

  • ADD.Sound compensates several orders of tonal gearbox vibrations at variable speed (over the entire speed range of the wind turbine)
  • One ADD.Sound active absorber 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)
  • 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