Sound immission measurement for wind farms and wind turbines
Sound immission measurement for wind farms: we determine the locally prevailing noise level at the relevant immission points, standard-compliant and accredited.
Wind is audible. So are wind turbines. Determining the locally prevailing sound immissions at the relevant immission points is the basis for an optimised wind farm layout, already in the preliminary design and permitting design. The measurement campaign is carried out by our accredited testing body, the EWS Testing Center, with calibrated, high-precision sensors. The measurements are independent, transparent and standard-compliant and last from 24 hours to several weeks depending on the task. Relevant immission points are those uses in the neighbourhood that are expected to be most affected by the wind farm.
What is measured is what is already there before construction. This is important because the background noise rises with wind speed and the turbine loses significance against the ambient noise in strong wind. If the background noise is well above the immission value of the turbine, its contribution to the total noise is smaller; however, a specific perceptibility cannot be derived from this alone. Sound and wind are therefore recorded at the same time and evaluated together. Wind speed is measured time-synchronously and, where necessary, related to the relevant height, taking into account measurement height, terrain and wind profile. In Austria, the base level LA,95 is the yardstick, i.e. the level exceeded for 95 per cent of the measurement time. The measurement follows ÖNORM S 5004; the planning guideline values result from the land zoning according to ÖNORM S 5021. The planning guideline value to be applied for the base level is to be determined on the basis of the zoning category, the version of the standard to be applied and the requirements of the authorities. Evaluation is carried out separately for day (6 am to 7 pm), evening (7 pm to 10 pm) and night (10 pm to 6 am). At very high wind speeds, the forecast becomes more uncertain because wind-induced ambient noise predominates.
Different requirements apply depending on the country. At sites in Austria, we determine wind-speed-dependent base levels in accordance with the Austrian requirements. At sites in Germany, we record the constantly present extraneous noise using a measurement method suited to the question at hand. There, the forecast is calculated according to DIN ISO 9613-2 and assessed at the immission points against the guideline values of TA Lärm. After construction, a verification measurement under suitable operating and ambient conditions can be used to check the permitted operating immissions. This makes sense because manufacturing tolerances or damage can lead to higher emissions. The sound emission of the turbine itself is determined separately according to ÖVE/ÖNORM EN 61400-11, and separate assessment criteria apply to low-frequency noise in the neighbourhood.
We leave no suitable measurement window unused so that your project can be implemented swiftly. The data form the basis for transparent communication with residents and authorities. They feed into the operational and construction noise assessment and the SEA specialist contributions for wind power. During ongoing operation, the sound emission measurement and frequency analysis follows where applicable. For photovoltaics there is the sound immission measurement for PV plants.
