Investigations on Low Frequency Noises of On-Shore Wind Turbines

Abstract

The expansion of renewable energy usage is one of the major social tasks in Europe and therefore requires acceptance and support from the population. In the case of onshore wind turbines, the complaints of local residents are often interpreted as infrasound disturbances conceivably caused by wind turbine operation. To improve the acceptance for wind energy projects, national standards and regulations need to incorporate such low frequency effects. This contribution presents long-term acoustic measurement data of low frequency noise recorded directly near wind turbines (emission) and inside of residential buildings (immission) with the objectives to identify the signal characteristics and main influential parameters. Different locations (wind farm and individual turbine), wind conditions, and time ranges are evaluated. It is shown that various frequency content below 150 Hz (harmonics of blade passing frequency, etc.) is connected to the rotation of the rotor blade and the operation of the generator. Furthermore, stable atmospheric conditions are determined to be of high importance for the transmission of the characteristic signals. For future research, this work also serves as an example for low frequency sound pressure data during operation and shutdown of wind turbines.

Assessment of low‐frequency aeroacoustic emissions of a wind turbine under rapidly changing wind conditions based on an aero‐servo‐elastic CFD simulation

“…It has been shown that the emitted low-frequency sound power of the tower depends on the rotational speed and on the wind speed, while the emissions of the blades are additionally influenced by the turbulence intensity. These numerical results match the findings from free-field measurements by Blumendeller et al, 15 who observed the same correlation between rotational speed and low-frequency sound emission, and by D'Amico et al, 17 who identified wind speed as well as turbulence intensity as dominant influencing factors. A yawed inflow is negligible for the sound emissions as long as it is not so large that the operating mode changes.…”

“…Low-frequency noise has a smaller dissipation factor in air and can travel farther than high-frequency noise. This was found in measurements 14,15 on the infrasound propagation for distance up to 10 km, especially for stable atmospheric conditions. Hence, the extent to which such low-frequency emissions can be perceived by humans living in the vicinity of the WT is the subject of intensive research and is sometimes controversially discussed.…”

Impact of wind turbine operation conditions on infrasonic and low frequency sound induced by on-shore wind turbines

“…In previous investigations, the BPF and its harmonics in the infrasonic frequency range could be clearly assigned to the WT operation [16]. Following the publication by Zajamšek et al [20], the 4th harmonic of the BPF is detected to identify infrasound occurrences.…”

“…Additionally meteorological measurements of wind speed and direction (with a 23 Hz sampling frequency), humidity, temperature and pressure (with a 10 Hz sampling frequency) were conducted at the WF site with a 10 m high met mast. More detailed information concerning the instrumentation, measurements, locations with surrounding conditions and schematics of the indoor measurement set-up can be found in [16,17].…”

Performance comparison of measurement microphones and microbarometers for sound pressure measurements near wind power plants

“…To date, various attempts have been made to determine noise levels at audible and infrasound frequencies. Blumendeller et al 4 used measurement microphones with two windscreen configurations, one conforming to IEC 61400-11 5 and a second using a windscreen box buried flush to the ground surface. Additionally, meteorological data were recorded near the measurement site.…”