Turbine Sound Effect

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Commissioned by the Swiss Federal Office for the Environment, an update of an earlier narrative review was prepared for the literature published between 2017 and mid-2020 about the effects of wind turbine sound on the health of local residents. Specific attention was hereby given to the health effects of low-frequency sound and infrasound. The Netherlands Institute for Public Health and the Environment and Mundonovo sound research collected the scientific literature on the effect of wind turbines on annoyance, sleep disturbance, cardiovascular disease, and metabolic effects, as well as mental and cognitive impacts. It also investigated what is known about annoyance from visual aspects of wind turbines and other non-acoustic factors, such as the local decision-making process. From the literature study, annoyance again came forward as the most important consequence of sound: the louder the sound (in dB) of wind turbines, the stronger the annoyance response was. The literature did not show that "low-frequency sound" (sound with a low pitch) results in extra annoyance on top of normal sound. Results of scientific research for other health effects are either not available or inconsistent, and we can conclude that a clear association with wind turbine related sound levels cannot be confirmed. There is evidence that long-term effects are related to the annoyance people experience. These results confirm earlier conclusions. There is increasing evidence that annoyance is lower when people can participate in the siting process. Worries of residents should be addressed in an early stage, by involving them in the process of planning and decision making.

In Germany several wind turbine parks have been and are being established in sparsely populated areas near the Dutch border. One of these is the Rhede Wind Park in northwestern Germany with seventeen 1.8 MW turbines of 98 m hub height and with 3-blade propellers of 35 m wing length. The turbines have a variable speed increasing with wind speed, starting with 10 r.p.m. (revolutions per minute) at a wind speed of 2.5 m/s at hub height up to 22 r.p.m. at wind speeds of 12 m/s and over.

At the Dutch side of the border is a residential area along the Oude Laan and Veendijk (see Fig. 1) in De Lethe: countryside dwellings surrounded by trees and agricultural fields. The dwelling nearest to the wind park is some 500 m west of the nearest wind turbine (W 16). According to a German noise assessment study a maximum immission level of 43 dB(A) was expected, 2 dB below the applied German noise limit. According to a Dutch consultancy immission levels would comply with Dutch (wind speed dependent) noise limits.

After the park was put into operation residents made complaints about the noise, especially at (late) evening and night-time. The residents, united in a neighbourhood group, could not persuade the German operator to put in place mitigation measures or to carry out an investigation of the noise problem and brought the case to court. The Science Shop for Physics had just released a report explaining a possible discrepancy between the calculated and the actual sound immission levels of the wind turbines because of changes in wind profile, and was asked to investigate the consequences of this discrepancy by sound measurements. Although at first the operator agreed to supply measurement data from the wind turbines (such as power output, rotation speed, axle direction), this was withdrawn after the measurements had started. All relevant data therefore had to be supplied or deduced from the author's own measurements.

There is a distinct audible difference between the night and daytime wind turbine sound at some distance from the turbines. On a summer's day in a moderate or even strong wind the turbines may only be heard within a few hundred metres and one might wonder why residents should complain of the sound produced by the wind park. However, on quiet nights the wind park can be heard at distances of up to several kilometres when the turbines rotate at high speed. On these nights, certainly at distances

Usually a fixed relation is assumed between the wind speed vh at height h and the wind speed vref at a reference height href (usually 10 m), which is the widely used logarithmic wind profile with surface roughness z as the only parameter. See for example the international recommendations for wind turbine noise emission measurements [4], [5]. For height h the wind speed vh is calculated as follows:vh=vreflog(h/z)/log(href/z).This equation is an approximation of the wind profile in the turbulent

Sound immission measurements were made over 1435 hours, of which 417 hours were at night, within four months at two consecutive locations with an unmanned Sound and Weather Measurement System (SWMS) consisting of a type 1 sound level meter with a microphone at 4.5 m height with a 9 cm diameter foam wind shield, and a wind meter at 10 m as well as at 2 m height. Every second, wind speed and wind direction (at 10 and 2 m height) and the A-weighted sound level were measured; the measured data are

From earlier measurements [3] a wind speed dependence of LW was established as given in Table 2. As explained above, the wind speed at 10 m height is not considered a reliable single measure for the turbine sound power. Rotational speed is a better measure.

From the 30 measurements of the equivalent sound level Leq,T (with T typically 5 min) measured at distance R from the turbine hub (R typically 1002m), a relation between sound power level LW and rotational speed N of a turbine could be determined: see Eq. (6).

This relation can be compared with the measured immission sound level Li,T (T=5 min) at location A, 400 m from the wind park (closest turbine), in 22 cases where the rotational speed was known. These measurements were taken at different times

Sound immission measurements have been made at 400 m (location A) and 1500 m (location B) from the wind park Rhede with 17 tall (98 m hub height), variable speed wind turbines. It is usual in wind turbine noise assessment to calculate immission sound levels assuming wind speeds based on wind speeds v10 at reference height (10 m) and a logarithmic wind profile. This study shows that the sound immission level may, at the same wind speed v10 at 10 m height, be significantly higher (up to 18 dB) during

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Wind power is one of the fastest growing energy sectors and is the focus of development in many countries around the world, especially in Europe. In 2007, European leaders agreed to source 20% of their energy needs from renewable sources. Wind turbines convert wind energy into electricity. Winds tend to be stronger and more uniform over the ocean than on land, and there are large, potentially productive areas available offshore.

During the operational stage of a wind farm, low frequency sound is produced when the blades are spinning. As a turbine operates, vibrations inside the nacelle (the housing that contains the generator, gearbox, and other parts) are transmitted down the main shaft of the wind turbine and into its foundation. These vibrations then propagate into the water column and seafloor. The sound is primarily below 1 kHz (generally below 700 Hz), with a source level of 80-150 dBre 1 Pa @ 1 m. Aerodynamic noise produced by the rotor blades may also enter the water through an airborne path. Sound levels increase slightly as wind speed increases. The type of wind turbine foundation will also affect the transmission of underwater sound.

Many offshore wind farms are constructed in coastal waters. Significant growth in offshore wind development has led to concern about the potential for negative impacts on fishes, marine mammals, invertebrates, birds, and bats. Potential negative effects include collision, habitat displacement, and exposure to electromagnetic fields and underwater noise.

There are limited data on long term effects associated with the continual operational noise of offshore wind turbines. The size of the turbines, overall size of the wind farm array, and where it is positioned, all have implications for environmental impact. In addition, cumulative effects associated with multiple wind farms in close proximity to each other, and increased human activities, such as shipping, in the area of the wind farms, are also poorly understood. Additional data are also necessary to understand effects due to long term shifts in prey availability around offshore wind installations.

Effects of noise from offshore wind farms depend on species sensitivity and site conditions. Caution should be exercised in extrapolating local measurements and results from one offshore wind facility to another. Turbine size and technology, foundation type, and the number and spacing of the turbines within the facility, as well as propagation conditions and ambient noise levels of each site, can be different and affect the sounds produced and how far they travel. Substrate type, local marine communities, and human activities before and after wind farm construction are also highly variable. The scale and size of each wind farm is also important to consider; small installations may have very localized effects.

In response to concerns, the American and Canadian Wind Energy Associations (AWEA and CanWEA) established a scientific advisory panel in early 2009 to conduct a review of current literature available on the issue of perceived health effects of wind turbines. This multidisciplinary panel is comprised of medical doctors, audiologists, and acoustical professionals from the United States, Canada, Denmark, and the United Kingdom. The objective of the panel was to provide an authoritative reference document for legislators, regulators, and anyone who wants to make sense of the conflicting information about wind turbine sound.

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