Testing Wind Turbines for Noise Emissions with NI LabVIEW
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Author(s):
Carsten Thomsen - DELTA
Bo Søndergaard - DELTA
Industry:
Energy/Power
Products:
NI-DAQmx, LabVIEW, PXI-4472
The Challenge:
Providing a standardized test system to measure the noise impact of wind turbines to comply with the International Electrotechnical Commission (IEC) and other standards.
The Solution:
Developing a custom measurement system that uses the NI PXI-4472 dynamic signal acquisition module to measure acoustic data from microphones and offers advanced measurement and analysis using Wind Turbine and noiseLAB software, two DELTA applications based in LabVIEW, to perform the required signal processing.
"We chose the LabVIEW development environment for our noiseLAB software because of the ability to use NI-DAQmx software as the core driver to program the NI PXI-4472 module, which gave us a high channel count at a low cost."
When planning a new wind farm, it is critical to consider the acoustic emissions. Engineers must optimize the wind farm layout factoring in meteorological conditions and terrain to minimize the noise impact on the surrounding community. To help engineers design wind farms by supplying data for predictions, DELTA, located in Hørsholm, Denmark, developed a custom measurement system called Wind Turbine for noise testing to ensure compliance with IEC 61400-11:2002 and other standards.
The IEC 61400-11:2002 standard provides a uniform methodology for measuring the noise emissions of a wind turbine under varying wind speeds to facilitate comparison between wind turbines. The standard is used by wind turbine manufacturers to specify noise emissions and by end customers to test whether specifications are met. The tests call for measurements of sound power level, one-third-octave band levels, and tonality at wind speeds from 6 to 10 m/s.
Developing a Measurement System Using the National Instruments Platform
At DELTA, we developed a measurement system using the NI PXI- 4472 dynamic signal acquisition module to acquire acoustic data from a microphone at the required frequencies. The microphone is placed on a board on the ground and supplied with a specialized secondary wind shield that complies with the IEC standard. The wind shield reduces the wind speed at the microphone and the wind-induced noise in the microphone, thus increasing the signal-to-noise ratio, especially at low frequencies.
We also developed our noiseLAB software using the LabVIEW graphical programming environment to record the acoustic data and perform the required SPL, octave, and tonality measurements. In most countries the tonality is determined according to ISO 1996-2 which is included in the noiseLAB software. We chose the LabVIEW development environment for our noiseLAB software because of the ability to use NI-DAQmx software as the core driver to program the NI PXI-4472 module, which gave us a high channel count at a low cost.
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