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Low-frequency noise from large wind turbines
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10.1121/1.3543957
/content/asa/journal/jasa/129/6/10.1121/1.3543957
http://aip.metastore.ingenta.com/content/asa/journal/jasa/129/6/10.1121/1.3543957

Figures

Image of FIG. 1.
FIG. 1.

(Color online) Apparent sound power levels (L WA and L WALF) in the reference direction as a function of turbine size. Wind speed is 8 m/s. Regression lines: all turbines included (thin lines), four turbines below 450 kW excluded (bold lines). Black-filled marks are for turbines 1–4.

Image of FIG. 2.
FIG. 2.

A-weighted apparent sound power levels in one-third-octave bands. Forty-five turbines with nominal electric power 75 kW–3.6 MW.

Image of FIG. 3.
FIG. 3.

Normalized A-weighted apparent sound power levels in one-third-octave bands. Forty-five turbines with nominal electric power 75 kW–3.6 MW. (Normalized meaning that L WA for the individual turbine has been subtracted from all one-third-octave-band levels.)

Image of FIG. 4.
FIG. 4.

(Color online) Normalized A-weighted apparent sound power levels in one-third-octave bands, means of two groups of turbines: ≤ 2 MW and > 2 MW. Error bars indicate ±1 standard error of mean.

Image of FIG. 5.
FIG. 5.

Normalized A-weighted apparent sound power levels in one-third-octave bands, mean of 36 turbines ≤ 2 MW (bold line) and 9 individual turbines > 2 MW.

Image of FIG. 6.
FIG. 6.

(Color online) Tonal audibility, ΔL ta, as a function of wind speed for turbines 1–4, reference direction (turbine color code as in Fig. 5).

Image of FIG. 7.
FIG. 7.

(Color online) Directivity of turbines 1–3. Wind speed is 8 m/s except for turbine 2, front, which was measured at 10 m/s (and compared to reference direction at 10 m/s). Data missing for turbine 2 front at 5 kHz due to electric noise in the measurement (turbine color code as in Fig. 5).

Image of FIG. 8.
FIG. 8.

(Color online) A-weighted apparent sound power level, L WA, as a function of wind speed for turbines 1–4 (turbine color code as in Fig. 5).

Image of FIG. 9.
FIG. 9.

A-weighted one-third-octave-band sound pressure levels at the distance from a single turbine, where the total A-weighted sound pressure level is 35 dB (see Table I and turbine color code as in Fig. 5).

Image of FIG. 10.
FIG. 10.

Sound insulation measured for ten rooms.

Image of FIG. 11.
FIG. 11.

Indoor A-weighted one-third-octave-band sound pressure levels at the distance from a single turbine, where the total A-weighted outdoor sound pressure level is 35 dB (see Table I); 81 turbine/room combinations. Dashed line is hearing threshold according to ISO 389–7 (Ref. 28) (colors indicate the turbine, color code as in Fig. 5).

Image of FIG. 12.
FIG. 12.

Indoor A-weighted one-third-octave-band sound pressure levels at the distance from wind farms, where the total A-weighted outdoor sound pressure level is 44 dB (see Table II); 81 turbine/room combinations. Dashed line is hearing threshold according to ISO 389–7 (Ref. 28) (colors indicate the turbine, color code as in Fig. 5).

Image of FIG. 13.
FIG. 13.

(Color online) Apparent sound power level (L WA) as a function of turbine size, four turbines below 450 kW excluded, wind speed 8 m/s. Linear regression line, standard error of estimates (s.e.e.) 1.64 dB. Extrapolation dashed, 90 % confidence intervals (dotted) based on s.e.e.

Image of FIG. 14.
FIG. 14.

(Color online) Normalized A-weighted apparent sound power levels in octave bands, means for two groups of turbines: < 2 and ≥ 2 MW. Data from van den Berg et al.,69 Appendix D. Error bars indicate ±1 standard error of mean. (None of the large turbines was measured in the 31.5-Hz octave band).

Image of FIG. 15.
FIG. 15.

(Color online) Normalized A-weighted apparent sound power levels in octave bands, means for two groups of turbines: < 2 and ≥ 2 MW and from two investigations: van den Berg et al. (Ref. 69), Appendix D and present investigation (converted to octave bands).

Image of FIG. 16.
FIG. 16.

Normalized A-weighted apparent sound power levels in one-third-octave bands, individual turbines > 2 MW and mean of 36 turbines ≤ 2 MW. Peaks in one-third-octave bands below 200 Hz have been removed from the large turbines by replacing the levels at the peaks by levels obtained by linear interpolation between the levels at the two adjacent one-third-octave-band frequencies (turbine color code as in Fig. 5).

Image of FIG. 17.
FIG. 17.

(Color online) Normalized apparent sound power levels in one-third-octave bands. Mean of two groups of turbines: ≤ 2 and > 2 MW, group of turbines ≤ 2 MW shifted one third of an octave down in frequency. (Turbine 6 disregarded above 2 kHz, see Sec. ???.)

Image of FIG. 18.
FIG. 18.

(Color online) Sixth-order polynomial regression (bold line) for mean of normalized apparent sound power levels (dots and thin line) for the turbines > 2 MW (Turbine 6 disregarded above 2 kHz, see Sec. ???.)

Image of FIG. 19.
FIG. 19.

(Color online) Estimated A-weighted sound power levels in one-third-octave bands for turbines around 2.5, 5, and 10 MW. Values and assumptions are taken from Table III.

Image of FIG. 20.
FIG. 20.

A-weighted sound pressure levels in one-third-octave bands at the distances, where the total A-weighted sound pressure level is 35 dB (see TableIV). Cylindrical propagation assumed from 200 m (turbine color code as in Fig. 5).

Tables

Generic image for table
TABLE I.

Key figures at the distances from a single turbine, where the total A-weighted sound pressure level is 35 dB. Distances are given as slant distance to rotor center, which, for actual turbine heights, is close to horizontal distance.

Generic image for table
TABLE II.

Key figures at the distances where the total A-weighted sound pressure level is 44 dB. Wind farm with two rows of each six identical turbines, 300 m distance between turbines in both directions (200 m for small turbines). Observer point centered at long side. Distances are given as slant distance to closest turbine.

Generic image for table
TABLE III.

Estimated relative and absolute A-weighted sound power levels for turbines around 2.5, 5, and 10 MW based on sixth-order polynomial approximation of mean relative spectrum for turbines above 2 MW from Fig. 18 and L WA from linear regression of Fig. 13. Relative levels moved, respectively, 1/6 and 1/3 of an octave down for 5 and 10 MW turbines. Approximation adjusted by +0.38 dB to achieve a total relative spectrum of 0 dB, which the mean of relative data (and its approximation) does not necessarily sum up to. Note that the estimates are based on means of turbines and that they do not include a safety margin as mentioned in Sec. IV B.

Generic image for table
TABLE IV.

Key figures at the distances, where the total A-weighted sound pressure level is 35 dB, cylindrical propagation assumed beyond 200 m. Distances are given as slant distance to rotor center, which, for actual turbine heights, is close to horizontal distance.

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/content/asa/journal/jasa/129/6/10.1121/1.3543957
2011-06-14
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Low-frequency noise from large wind turbines
http://aip.metastore.ingenta.com/content/asa/journal/jasa/129/6/10.1121/1.3543957
10.1121/1.3543957
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