Results of simultaneous acoustic measurements around a large horizontal axis wind turbine

Hubbard, Harvey H.; Shepherd, Kevin P.; Willshire, William L.

doi:10.1121/1.2023732

Cited by 3 publications

(1 citation statement)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…11 An extensive experimental study of propagation of wind turbine noise at the 10-Hz one-third octave band out to 20 km has also been carried out together with a theoretical analysis. 12,13 However, as far as we know, there have not yet been published any results of comparison of experiments and FFP predictions of propagation of impulse, infrasound frequencies at the ranges studied here ͑out to 1400 m͒. To give reliable predictions of propagation of sound in the frequency range studied here is of practical interest, since atmospheric absorption is weak, about 0.1 to 0.5 dB/km.…”

Section: Introductionmentioning

confidence: 90%

Effects of strong sound velocity gradients on propagation of low-frequency impulse sound: Comparison of fast field program predictions and experimental data

Hole

Lunde

Gjessing³

1997

The Journal of the Acoustical Society of America

View full text Add to dashboard Cite

As part of a large outdoor sound propagation experiment series, propagation of low-frequency impluse sound at ranges from 100 to 1400 m was studied at Haslemoen, Norway in February 1995. Sound sources were charges of 1 and 8 kg C4 explosives. Experiments were carried out in both a uniform forest and above a flat and uniform open field. Extensive meteorological measurements were carried out. Both automatic weather stations mounted in permanent towers and a tethered balloon were employed. The measurements resulted in a manifold set of sound velocity profiles. Occasionally, profiles were pure downwind or upwind, but mostly they were complex, often with large vertical gradients. One conclusion is that one should not uncritically use simple profile parameterizations, e.g., logarithmic, in sound propagation models. A fast field program (FFP), CAPROS, handles the complex sound-speed profiles well, predicting propagation of sound at 8, 16, 32.5, and 63 Hz. In this model, ground is considered a viscoelastic medium. At 63 Hz, the forest seems to cause an excess attenuation. At the lower frequencies, distinct effects of forest are not observed. There is no evidence that FFP predictions are less accurate in periods with high turbulence levels, which is here characterized with dynamical instability. However, variability of meteorological profiles causes predictions to be less accurate. This investigation suggests that it is sufficient to sample atmospheric variables up to 300 m above ground to predict sound propagation at the ranges studied here.

show abstract

Section: Introductionmentioning

confidence: 90%

Effects of strong sound velocity gradients on propagation of low-frequency impulse sound: Comparison of fast field program predictions and experimental data

Hole

Lunde

Gjessing³

1997

The Journal of the Acoustical Society of America

View full text Add to dashboard Cite

show abstract

Application of a ray theory model to the prediction of noise emissions from isolated wind turbines and wind parks

Prospathopoulos

Voutsinas

2006

Wind Energy

View full text Add to dashboard Cite

Various propagation models have been developed to estimate the level of noise near residential areas. Predictions and measurements have proven that proper modelling of the propagation medium is of particular importance. In the present work, calculations are performed using a ray theory methodology. The ray trajectory and transport equations are derived from the linear acoustics equations for a moving medium in three dimensions. Ground and atmospheric absorption, wave refraction and diffraction and atmospheric turbulence are taken into account by introducing appropriate coefficients in the equations. In the case of a wind turbine (W/T) it is assumed that noise is produced by a point source located at the rotor centre. Given the sound power spectrum, the noise spectrum at the receiver is obtained by solving the axisymmetric propagation problem. The procedure consists of (a) finding the eigenrays, (b) calculating the energy losses along the eigenrays and (c) synthesizing the sound pressure level (SPL) by superposing the contributions of the eigenrays. In the case of a wind park the total SPL is calculated by superposing the contributions of all W/Ts. Application is made to five cases of isolated W/Ts in terrains of varying complexity. In flat or even smooth terrain the predictions agree well with the measurements. In complex terrain the predictions can be considered satisfactory, taking into account the assumption of constant wind velocity profile. Application to a wind park shows clearly the influence of the terrain on the wind velocity and consequently on the SPL. Copyright © 2006 John Wiley &Sons, Ltd.

show abstract

Application of ray theory to propagation of low-frequency noise from wind turbines

Hawkins

1987

The Journal of the Acoustical Society of America

View full text Add to dashboard Cite

Ray theory has been used to attempt to explain the propagation of very low-frequency (1–20 Hz) noise generated by downwind wind turbines. Two NASA field experiments with a large downwind machine at Medicine Bow, Wyoming, show that the downwind sound decays by spherical spreading near the source, but by cylindrical spreading downrange. Ray theory calculations explain this behavior. The favorable wind gradient downwind causes rays to refract downward and bounce along the ground. A sound channel is built up by repeated jumps in the number of ray arrivals at the receiver as downwind range is increased. Near the source, where no multiply reflected rays arrive, the sound field spreads spherically. The first jump (onset of multiple arrivals) is predicted to occur at about 2 km for the conditions of the NASA experiments. The second NASA experiment confirms this prediction. For the upwind sound, a shadow zone is predicted because of the unfavorable wind gradient. The NASA measurements show only that the upwind SPL in the predicted shadow zone is of order 7–15 dB less than the downwind SPL at comparable ranges. [Work supported by NASA.]

show abstract

Results of simultaneous acoustic measurements around a large horizontal axis wind turbine

Cited by 3 publications

References 0 publications

Effects of strong sound velocity gradients on propagation of low-frequency impulse sound: Comparison of fast field program predictions and experimental data

Effects of strong sound velocity gradients on propagation of low-frequency impulse sound: Comparison of fast field program predictions and experimental data

Application of a ray theory model to the prediction of noise emissions from isolated wind turbines and wind parks

Application of ray theory to propagation of low-frequency noise from wind turbines

Contact Info

Product

Resources

About