Wind Turbine Noise Propagation Research Articles

Validity of the effective sound speed approximation in parabolic equation models for wind turbine noise propagation.

Parabolic equation (PE) based methods are widely used in outdoor acoustics because they can solve acoustic propagation problems above a mixed ground in a refractive and scattering atmosphere. However, recent research has shown phase error due to the effective sound speed approximation (ESSA). To overcome these limitations, a new PE formulation derived without the ESSA has been proposed recently. We investigate the impact of such phase error on wind turbine noise modeling, as the classical wide-angle parabolic equation (WAPE) with ESSA is widely used in the research community. We propose a comparison between the classical WAPE with ESSA and the new WAPE derived without the ESSA in the context of wind turbine noise. We highlight large phase error (several dB) on monochromatic calculations with a point source. Using an extended sound source representative of a wind turbine, we show small phase error (<1 dB) in a wind turbine noise context where sound level variability far from the source is of several dB. The validity of previous works using WAPE with ESSA is, thus, not questioned, although we do recommend the use of the new WAPE derived without the ESSA to accurately model the effect of wind speed on sound propagation.

A large-scale, long-term experimental campaign for the investigation of wind turbine noise fluctuations and amplitude modulation phenomena.

The understanding and prediction of wind turbine noise (WTN) remain a subject on which progress is needed to better address the concerns of residents of some wind farms and to help wind farm operators to better optimize their wind farms. A large-scale and long-term measurement campaign was conducted by partners of the PIBE project (https://www.anr-pibe.com/en) near a French wind farm during 430 days, in order to study the emission and propagation of WTN. The campaign provided 100ms sound levels and acoustic spectra, together with periodically recorded 2 min audio samples, at 5 locations ranging from 350m to 1.3km from the wind farm, in different propagation directions. Meteorological data were simultaneously collected by a 80m meteorological mast, one or two Lidars and sonic anemometers, in order to characterize vertical profiles of wind speed, wind direction, temperature, and wind turbulence. 2 distinct weeks of intensive measurements (one in summer and one in winter) completed the data by including 15 additional acoustic points at other locations. The database will mainly be used within the project for the investigation of an uncertainty model of WTN, and of WTN amplitude modulations. This communication presents the database and first results about temporal variabilities of WTN.

Criteria for the assessment of the influence of atmospheric turbulence on wind turbine noise propagation

This paper investigates the influence of atmospheric turbulence on the propagation of wind turbine noise using an aeroacoustic source model coupled with a parabolic equation propagation model. Sets of simulations with and without atmospheric turbulence are performed, allowing the determination of a simple formulation that quantifies the uncertainties of the A-weighted sound pressure level (SPL) when the modelling does not account for atmospheric turbulence. For the case study, the results show that atmospheric turbulence has a negligible effect on SPL up to 800 m from the wind turbine, even under upwind conditions. While the conclusions are specific to this case study, the method appears promising for simplifying the calculation of atmospheric turbulence effect in wind turbine noise studies. A freely accessible online application has been developed to present additional results.

Propagation of wind turbine noise: measurements and model evaluation

Sound propagation from wind turbines through the atmosphere has previously been analytically examined through numerous studies, but the amount of comparisons to measurements is limited. This paper applies three different sound propagation models; The ISO 9613-2 model, the Nord2000 ray tracing model and the WindSTAR-Pro model, to evaluate the noise at receivers in the near- and far-field of a wind turbine. The evaluation is performed by accounting for different meteorological and terrain parameters. For validation purposes, the study further uses two different data sets from measurement campaigns; Loudspeaker noise and wind turbine noise measurements. The validation evidently shows that especially the WindSTAR-Pro model and the Nord2000 model provide good agreement to the measurements for some of the validation cases, while other results are heavily influenced by the turbine wake, signal to noise ratio in the measurements or directivity of the noise source.

Noise Propagation Calculations of a Wind Turbine in Complex Terrain

This paper describes numerical noise propagation calculations of a single wind turbine in complex terrain near a town in Central Denmark. The purpose of the work is to estimate the noise level at increasing distances from a single wind turbine and investigate the effect of complex terrain. Results indicate that time varying numerical noise propagation predictions of wind turbines in complex terrain can be achieved by using computational fluid dynamics via large-eddy simulation (LES) and the Technical University of Denmark’s noise propagation tool based on the parabolic equation. The wind turbine is modeled using the actuator line approach. The results from this project will have significant social, environmental, and economic impact, since accurate predictions of wind turbine noise propagation can be used to develop noise mitigation strategies to increase the public acceptance of wind energy.

Extended source models for wind turbine noise propagation.

Accurate prediction of wind turbine noise propagation over long distances requires modeling the dominant broadband aerodynamic noise sources, as well as the main outdoor sound propagation effects. In this study, two methods are compared to include extended aeroacoustic source models in a parabolic equation (PE) code for wind turbine noise propagation in an inhomogeneous atmosphere. In the first method, an initial starter is obtained for each segment of the blade using the backpropagation approach. In the second method, the blade segments are viewed as moving monopole sources, and only a limited number of PE simulations are needed for different source heights across the rotor plane. The two methods are compared to the point source approximation first in a homogeneous medium for validation purposes, and then in a stratified inhomogeneous atmosphere. The results show that an extended source model is necessary to calculate the sound pressure level upwind, where a shadow zone is present, and obtain the correct amplitude modulation levels. Furthermore, the second method is seen to yield as accurate results as the first method when a sufficient number of source heights is considered with a computation time that is much reduced.

Development of an Efficient Numerical Method for Wind Turbine Flow, Sound Generation, and Propagation under Multi-Wake Conditions

The propagation of aerodynamic noise from multi-wind turbines is studied. An efficient hybrid method is developed to jointly predict the aerodynamic and aeroacoustics performances of wind turbines, such as blade loading, rotor power, rotor aerodynamic noise sources, and propagation of noise. This numerical method combined the simulations of wind turbine flow, noise source and its propagation which is solved for long propagation path and under complex flow environment. The results from computational fluid dynamics (CFD) calculations not only provide wind turbine power and thrust information, but also provide detailed wake flow. The wake flow is computed with a 2D actuator disc (AD) method that is based on the axisymmetric flow assumption. The relative inflow velocity and angle of attack (AOA) of each blade element form input data to the noise source model. The noise source is also the initial condition for the wave equation that solves long distance noise propagation in frequency domain. Simulations were conducted under different atmospheric conditions which showed that wake flow is an important part that has to be included in wind turbine noise propagation.

Prediction of wind turbine noise propagation

In order to meet the US Department of Energy’s projected target of 35% of the US energy coming from wind by 2035, there is a strong need to look into the management and development of wind turbine technology and its impacts on human health, wild life, and the environment. The prediction of wind turbine noise and its propagation is very critical to study the impacts of wind turbine noise for long-term adoption and acceptance by neighboring communities. This article presents a study on the prediction of wind turbine noise propagation using an open access software and the publicly available topological map of projected sites. The noise propagation prediction utilized Openwind, a software package used for wind project design and optimization, to generate a noise map based on inputs acquired from a potential wind energy demonstration site. The predicted noise maps were incorporated with the measured ambient noise data to predict the resultant noise level in the surrounding neighborhood under different scenarios.

Coupling of an aeroacoustic model and a parabolic equation code for long range wind turbine noise propagation

This study proposes to couple a source model based on Amiet's theory and a parabolic equation code in order to model wind turbine noise emission and propagation in an inhomogeneous atmosphere. Two broadband noise generation mechanisms are considered, namely trailing edge noise and turbulent inflow noise. The effects of wind shear and atmospheric turbulence are taken into account using the Monin-Obukhov similarity theory. The coupling approach, based on the backpropagation method to preserve the directivity of the aeroacoustic sources, is validated by comparison with an analytical solution for the propagation over a finite impedance ground in a homogeneous atmosphere. The influence of refraction effects is then analyzed for different directions of propagation. The spectrum modification related to the ground effect and the presence of a shadow zone for upwind receivers are emphasized. The validity of the point source approximation that is often used in wind turbine noise propagation models is finally assessed. This approximation exaggerates the interference dips in the spectra, and is not able to correctly predict the amplitude modulation.

Consistent modelling of wind turbine noise propagation from source to receiver

The unsteady nature of wind turbine noise is a major reason for annoyance. The variation of far-field sound pressure levels is not only caused by the continuous change in wind turbine noise source levels but also by the unsteady flow field and the ground characteristics between the turbine and receiver. To take these phenomena into account, a consistent numerical technique that models the sound propagation from the source to receiver is developed. Large eddy simulation with an actuator line technique is employed for the flow modelling and the corresponding flow fields are used to simulate sound generation and propagation. The local blade relative velocity, angle of attack, and turbulence characteristics are input to the sound generation model. Time-dependent blade locations and the velocity between the noise source and receiver are considered within a quasi-3D propagation model. Long-range noise propagation of a 5 MW wind turbine is investigated. Sound pressure level time series evaluated at the source time are studied for varying wind speeds, surface roughness, and ground impedances within a 2000 m radius from the turbine.

Extended source models for long range wind turbine noise propagation

Wind turbine noise can be perceived at distances greater than one kilometer and is characterized by amplitude modulations at the receiver. In order to predict this noise, it is necessary to model the dominant aeroacoustic noise sources as well as the main outdoor propagation effects. In most studies from the literature, the wind turbines are modeled as point sources to simplify the coupling between source and propagation models, but this assumption is not always justified. In this study, two original methods are proposed to couple an aeroacoustic source model based on Amiet’s theory and a Split-Step Padé parabolic equation code for acoustic propagation in an inhomogeneous atmosphere. In the first method, an initial starter is obtained for each segment of the blade using the backpropagation approach. This method enables us to accurately model the directivity of the noise sources but is very computationally intensive. In the second method, the blade segments are viewed as moving monopole sources, and only a limited number of parabolic equation simulations are needed which strongly reduces the computation time. These two methods are validated using an analytical reference solution in a homogeneous medium and compared in various inhomogeneous atmospheres.

Prediction of far-field wind turbine noise propagation with parabolic equation.

Sound propagation of wind farms is typically simulated by the use of engineering tools that are neglecting some atmospheric conditions and terrain effects. Wind and temperature profiles, however, can affect the propagation of sound and thus the perceived sound in the far field. A better understanding and application of those effects would allow a more optimized farm operation towards meeting noise regulations and optimizing energy yield. This paper presents the parabolic equation (PE) model development for accurate wind turbine noise propagation. The model is validated against analytic solutions for a uniform sound speed profile, benchmark problems for nonuniform sound speed profiles, and field sound test data for real environmental acoustics. It is shown that PE provides good agreement with the measured data, except upwind propagation cases in which turbulence scattering is important. Finally, the PE model uses computational fluid dynamics results as input to accurately predict sound propagation for complex flows such as wake flows. It is demonstrated that wake flows significantly modify the sound propagation characteristics.

Propagation of wind turbine noise through the turbulent atmosphere

It is well known that turbulence can cause fluctuations in the resulting sound fields. In the issue of wind turbine noise, such effect is non-negligible since either the inflow turbulence from nearby turbine wakes or the atmospheric turbulence generated by rotating turbine blades can increase the sound output of individual turbines. In this study, a combined approach of the Finite Element Method (FEM) and Parabolic Equation (PE) method is employed to predict the sound levels from a wind turbine. In the prediction procedure, the near field acoustic data is obtained by means of a computational fluid dynamic program which serves as a good starting field of sound propagation. It is then possible to advance wind turbine noise in range by using the FEM/PE marching algorithm. By incorporating the simulated turbulence profiles near wind turbine, more accurate predictions of sound field in realistic atmospheric conditions are obtained.

Finite Difference Simulation for High-Accuracy Prediction of Wind Turbine Noise Propagation

Finite Difference Simulation for High-Accuracy Prediction of Wind Turbine Noise Propagation

Wind turbine noise propagation: Comparison of measurements and predictions by a method based on geometrical ray theory

The objective of the present work has been to investigate the accuracy of the Nord2000 propagation model when used to predict noise from high sources like wind turbines. The model is representative to a new generation of �engineering� models developed on basis of analytical and heuristic solutions. The accuracy is investigated by comparison with measurements. Three experiments have been carried out for this purpose: 1) downwind and upwind propagation over flat grass-covered ground from an elevated loudspeaker, 2) downwind and upwind propagation over non-flat ground from a loudspeaker placed on top of a wind turbine nacelle, and 3) downwind propagation over non-flat ground from a single wind turbine. Experiment 1) showed for downwind propagation a very fine agreement between measured and predicted A-weighted noise levels in the considered range of propagation distances (1500 m). The bias error was 0.1 dB with a standard uncertainty of 0.7 dB. The agreement for upwind propagation was not as good. In experiment 2) the accuracy was slightly reduced compared to the downwind results of experiment 1) with a bias error of 0.5 dB and a standard uncertainty of 1.9 dB. In experiment 3) where a wind turbine was used as source the agreement was less than seen in the loudspeaker experiments.

Finite Difference Simulation for High-Accuracy Prediction of Wind Turbine Noise Propagation

Finite Difference Simulation for High-Accuracy Prediction of Wind Turbine Noise Propagation

Wind Turbine Noise Propagation over Flat Ground: Measurements and Predictions

Noise from wind turbines is of concern in the planning process of new wind farms, and accurate estimations of immission noise levels at residents nearby are required. Sound propagation from wind turbine to receiver could be modelled by a simplified standard model assuming constant meteorological conditions, by an engineering method taking atmospheric and ground propagation conditions into account, or by a more exact model. Epidemiological studies have found a higher frequency of annoyance due to wind turbine noise than to other community noise sources at equal noise levels, indicating that the often used simplified model is not sufficient. This paper evaluates the variation of immission sound levels under the influence of meteorological variation and explores if the prediction of levels could be improved by taking the effect of wind speed on sound propagation into account. Long-term sound recordings and measurements at a distance of 530 m from a wind turbine show that the simplified standard model predicts the average sound pressure levels satisfactorily under downwind conditions, and that a more complex propagation model might not be needed for wind turbine noise at a relatively short distance. Large variations of sound immission levels at the same wind speed were however present. Statistical analysis revealed that these variations were influenced by meteorological parameters, such as temperature, static pressure and deviation from ideal downwind direction. The overall results indicate that meteorological factors influence the noise generated by the wind turbine rather than the sound propagation.

Methodologies to address limitations of the ISO9613‐2 standard for wind turbine noise propagation modeling.

The accuracy of the noise propagation modeling results is dependent on: (1) the sound source data entered into the model as reported by wind turbine equipment manufacturers as specified under per IEC 64100‐11 standard; (2) site specific topographical, meteorological, and terrain conditions; and (3) the propagation algorithms of the acoustic modeling standard that are applied. For wind energy facilities sited in the US, the ISO 9613‐2 standard is most commonly used due to its proven effectiveness to accurately predict the sound levels at a distance for industrial and commercial projects in an outdoor environment. The propagation algorithms employed by the ISO 9613‐2 standard account for geometrical divergence, atmospheric absorption, ground attenuation, screening effects, and favorable sound propagation conditions that would occur during omnidirectional downwind meteorological conditions. The purpose of this paper is to identify limitations inherent in the ISO 9613‐2 standard to the specialized application of wind turbine acoustics and nonstandard atmospheric conditions. Methodologies are presented to more accurately describe atmospheric and lateral attenuation effects, which can result in significant uncertainties in the noise levels calculated both in proximity and at distant receptor locations.

Three-Dimensional Effects on Sound Propagation and Matched-Field Processor Performance

Journal of Computational AcousticsVol. 09, No. 01, pp. 17-39 (2001) No AccessTHREE-DIMENSIONAL EFFECTS ON SOUND PROPAGATION AND MATCHED-FIELD PROCESSOR PERFORMANCEJUAN I. ARVELO and ALLAN P. ROSENBERGJUAN I. ARVELOJohns Hopkins University, Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099, USA Search for more papers by this author and ALLAN P. ROSENBERGJohns Hopkins University, Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723-6099, USA Search for more papers by this author https://doi.org/10.1142/S0218396X01000413Cited by:11 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail AbstractThe most recent 2-D split-step Padé parabolic-equation model was modified to include narrow-angle azimuthal coupling. This model was developed and applied to the Santa Barbara channel to assess the effect of 3-D propagation on the performance of a matched-field processor. These results, plus those from the Shallow Water Acoustic Modeling (SWAM) workshop's 3-D wedge and the Gaussian canyon cases, will demonstrate the importance of azimuthal coupling to sound propagation in littoral regions and its effect on the performance of a matched-field processor. Special emphasis is given to model limitations and suitable selection of model parameters that could be automated to achieve accurate predictions during production runs. FiguresReferencesRelatedDetailsCited By 11Measurements and modeling of acoustic propagation in a scale model canyonMegan S. Ballard and Jason D. Sagers1 Sep 2019 | The Journal of the Acoustical Society of America, Vol. 146, No. 3Developments of parabolic equation method in the period of 2000–2016Chuan-Xiu Xu, Jun Tang, Sheng-Chun Piao, Jia-Qi Liu and Shi-Zhao Zhang29 November 2016 | Chinese Physics B, Vol. 25, No. 12Leading-order cross term correction of three-dimensional parabolic equation modelsFrédéric Sturm1 Jan 2016 | The Journal of the Acoustical Society of America, Vol. 139, No. 1Normal Mode Analysis of Three-Dimensional Propagation Over a Small-Slope Cosine Shaped HillMegan S. Ballard, Benjamin M. Goldsberry, and Marcia J. Isakson25 June 2015 | Journal of Computational Acoustics, Vol. 23, No. 03A three dimensional parabolic equation method for sound propagation in moving inhomogeneous mediaRui Cheng, Philip J. Morris and Kenneth S. Brentner1 Jan 2009 | The Journal of the Acoustical Society of America, Vol. 126, No. 4INVESTIGATION OF 3D ACOUSTICAL EFFECTS USING A MULTIPROCESSING PARABOLIC EQUATION BASED ALGORITHMK. CASTOR and F. STURM21 November 2011 | Journal of Computational Acoustics, Vol. 16, No. 02ACCURATE TREATMENT OF A GENERAL SLOPING INTERFACE IN A FINITE-ELEMENT 3D NARROW-ANGLE PE MODELFRÉDÉRIC STURM and NIKOLAOS A. KAMPANIS21 November 2011 | Journal of Computational Acoustics, Vol. 15, No. 03A 3D Parabolic Equation Method for Sound Propagation in Moving Inhomogeneous MediaRui Cheng, Philip Morris and Kenneth Brentner4 November 2007A 3D Parabolic Equation Method for Wind Turbine Noise Propagation in Moving Inhomogeneous AtmosphereRui Cheng, Philip Morris and Kenneth Brentner11 November 2006Numerical study of broadband sound pulse propagation in three-dimensional oceanic waveguidesFrédéric Sturm1 Mar 2005 | The Journal of the Acoustical Society of America, Vol. 117, No. 3On the use of higher-order azimuthal schemes in 3-D PE modelingFrédéric Sturm and John A. Fawcett1 Jan 2003 | The Journal of the Acoustical Society of America, Vol. 113, No. 6 Recommended Vol. 09, No. 01 Metrics History Received 1 January 2000 Revised 1 June 2000 PDF download