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Wind turbines emit infrasound and low-frequency noise (ILFN), which can be annoying for people living near wind farms. To assess the acoustic impact of wind turbines on the environment, it is essential to model ILFN propagation during the forecasting stage. This study assesses the effectiveness of three commonly used sound propagation models (ISO 9613-2, CNOSSOS-EU for favourable propagation conditions, Nord2000) in predicting ILFN generated by wind turbines. The performance of these models in modelling ILFN is generally not validated or guaranteed. The analysis covers octave frequency bands ranging from 4 Hz to 250 Hz, and comparisons are made against measurements conducted at a wind farm in Poland. Non-parametric statistical tests were used with a significance level of α = 0.05 to determine significant differences between measured and predicted results. The results show that the Nord2000 method provides accurate calculations, while the ISO 9613-2 method can be used for simplified assessments of ILFN generated by wind turbines during the investment preparation phase. [ABSTRACT FROM AUTHOR]

This study used accelerometers and hydrophones to measure the vibration and underwater noise from two different types of offshore wind turbine installed near the East China Sea Bridge (Shanghai). Wind speed and rotor speed were also monitored synchronously. The spectrograms of the vibration and underwater noise signals display well-defined spectral lines that are easily distinguishable. Line-component spectra of both vibration and underwater noise signals were synchronously extracted through filtering and correlation analysis. On this basis, relationships between the intensity and frequency of wind turbine vibration and underwater noise line-component spectra, rotor speed, and wind speed were analyzed. Results indicate that rotor speed is positively correlated with wind speed, and that the peak vibration frequencies and intensities of both types of turbine are positively correlated with rotor speed. Consequently, it can be concluded that the frequency and intensity of turbine-generated underwater noise are closely related to wind speed. Additionally, the vibration mechanism and the characterization of underwater noise of the wind turbines have been revealed. [ABSTRACT FROM AUTHOR]

Amplitude modulated noise from a single wind turbine is considered. The time-varying modulation depth D_m and the short time-average sound level L_Aeq,τ (with τ = 20 s) are measured at the reference distance d_*. Due to amplitude modulation, a penalty has to be added to L_Aeq,τ. The paper shows how to calculate the corrected long-term time-average sound level L ̂_AeqT (with T >> 20 s), which accounts for amplitude modulation, at any distance d ≠ d_* from the wind turbine. The proposed methodology needs to be tested by research

Wind turbines emit infrasound and low-frequency noise (ILFN), which can be annoying for people living near wind farms. To assess the acoustic impact of wind turbines on the environment, it is essential to model ILFN propagation during the forecasting stage. This study assesses the effectiveness of three commonly used sound propagation models (ISO 9613-2, CNOSSOS-EU for favourable propagation conditions, Nord2000) in predicting ILFN generated by wind turbines. The performance of these models in modelling ILFN is generally not validated or guaranteed. The analysis covers octave frequency bands ranging from 4 Hz to 250 Hz, and comparisons are made against measurements conducted at a wind farm in Poland. Non-parametric statistical tests were used with a significance level of α=0.05 to determine significant differences between measured and predicted results. The results show that the Nord2000 method provides accurate calculations, while the ISO 9613-2 method can be used for simplified assessments of ILFN generated by wind turbines during the investment preparation phase.

Abstract The rotor of a large diameter wind turbine experiences more substantial and more dynamic loads due to the fluctuating and heterogeneous wind field. The project SmartBlades 2.0 investigated rotor blade design concepts that alleviate aerodynamic loading using active and passive mechanisms. The present work evaluates the acoustics of the two load alleviating concepts separately, an inboard slat and an outboard flap, using the Fast Random Particle Mesh/Fast Multipole Code for Acoustic Shielding (FRPM/FMCAS) numerical prediction toolchain developed at DLR with input from the averaged flow field from RANS. The numerical tools produce a comparable flap side‐edge noise spectrum with that of the measurement conducted in the Acoustic Wind Tunnel Braunschweig (AWB). The validated FRPM/FMCAS was then used to analyze the self‐noise from a slat at the inboard section of a rotor blade with a 44.45 m radius and compared with that from the outboard trailing edge. Furthermore, the rotational effect of the rotor was included in the post‐processing to emulate the noise observed at ground level. The findings show an increase in the slat's overall sound pressure level and a maximum radiation upwind of the wind turbine for the case with the largest wind speed that represents the off‐design condition. In operational conditions, the slat adds at most 2 dB to the overall sound pressure level. The toolchain evaluates wind turbine noise with conventional or unconventional blade design, and the problem can be scaled up for a full‐scale analysis. As such, the tools presented can be used to design low‐noise wind turbines efficiently.

The noise emission of wind turbines and farms can be an important and limiting factor for future cost reductions and growth of wind energy. Closing scientific and technological gaps on wind turbine noise is thus directly supporting the further development of renewable energy while reducing adverse reactions toward wind farms. The present article is providing guidance on the most relevant research directions from an engineering perspective, namely: simulation methods, wind tunnel testing, and wind turbine design. Each topic is addressed separately and specific scientific challenges are identified. Future research directions that may improve our physical understanding of wind turbine noise, as well as facilitate the deployment of wind energy, are outlined. It is concluded that future scientific research on the topic of wind turbine noise should be conducted in a multidisciplinary context to maximize its impact. The suggested topics shall be seen as a collection of what is seen as the most relevant topics across research and product development but shall not be seen as exclusive or interlinked with specific development plans. This article is categorized under:Sustainable Energy > Wind EnergyHuman and Social Dimensions > Social Acceptance [ABSTRACT FROM AUTHOR]

Amplitude-modulated noise from a single wind turbine is considered. The time-varying modulation depth Dm and the short time-average sound level LAeq, τ; (with τ = 20 s) are measured at the reference distance d* Due to amplitude modulation, a penalty has to be added to LAeq, τ. The paper shows how to calculate the corrected long-term time-average sound level LAeq;,Τ (with Τ >> 20 s), which accounts for amplitude modulation at any distance d ≠ d* from the wind turbine. The proposed methodology needs to be tested by research. [ABSTRACT FROM AUTHOR]

This work presents the application and validation of a novel auralization approach for the evaluation of wind turbine noise annoyance under diverse conditions. The approach is based on the decomposition of each turbine blade into elementary short-segment sources, whose acoustic radiation in the far field is obtained by coupling Amiet’s emission model with the Harmonoise engineering model for outdoor sound propagation. The transfer functions between the elementary source positions and receivers are obtained. Then, the average and instantaneous sound pressure levels are calculated over one blade rotation. The realism of the audio signals is evaluated through listening tests with audio signals of the real and simulated environments. The predicted noise spectra from five wind turbines capture well the measured trends and the absolute levels. Finally, we present a study of the weather effects on noise emissions and propagation by using the numerical model developed.

The rotor of a large diameter wind turbine experiences more substantial and more dynamic loads due to the fluctuating and heterogeneous wind field. The project SmartBlades 2.0 investigated rotor blade design concepts that alleviate aerodynamic loading using active and passive mechanisms. The present work evaluates the acoustics of the two load alleviating concepts separately, an inboard slat and an outboard flap, using the Fast Random Particle Mesh/Fast Multipole Code for Acoustic Shielding (FRPM/FMCAS) numerical prediction toolchain developed at DLR with input from the averaged flow field from RANS. The numerical tools produce a comparable flap side‐edge noise spectrum with that of the measurement conducted in the Acoustic Wind Tunnel Braunschweig (AWB). The validated FRPM/FMCAS was then used to analyze the self‐noise from a slat at the inboard section of a rotor blade with a 44.45 m radius and compared with that from the outboard trailing edge. Furthermore, the rotational effect of the rotor was included in the post‐processing to emulate the noise observed at ground level. The findings show an increase in the slat's overall sound pressure level and a maximum radiation upwind of the wind turbine for the case with the largest wind speed that represents the off‐design condition. In operational conditions, the slat adds at most 2 dB to the overall sound pressure level. The toolchain evaluates wind turbine noise with conventional or unconventional blade design, and the problem can be scaled up for a full‐scale analysis. As such, the tools presented can be used to design low‐noise wind turbines efficiently. [ABSTRACT FROM AUTHOR]

Amplitude modulation increases the annoyance caused by wind turbine noise. One gets the improved annoyance when a penalty is added to the measured or calculated time-average sound level. The amplitude modulated wind turbine noise consists of pulses. Each of them could be characterized by the short timeaverage sound level and the modulation depth. The latter determines the pulse penalty. This paper shows how to calculate the improved annoyance of amplitude modulated wind turbine noise, when the short time-average sound level and the penalty for each pulse are known. A special case of identical pulses is discussed. The proposed methodology needs to be tested by research.

Abstract An experimental investigation on scaled wind turbine models in a wind tunnel with a microphone array is presented. Our study focuses on the localization and quantification of aerodynamic noise sources on rotating wind turbine blades with the aim of identifying the contributing factors that have an impact on the source spectra. Therefore, wind tunnel measurements were conducted for three different blade geometries (NACA 4412 shape, Clark‐Y shape, and sickle shape), five pitch angles between −2° and +8° and five wind velocities between 5 and 13 mŝ−1. For the localization of rotating sound sources with a microphone array, a rotating beamforming method based on the acoustic ray method is used. The Clean‐SC deconvolution method was used to improve the resolution of the acoustic sources, and integrated spectra were calculated for the individual blades. The sound sources were localized at the wind turbine blades and assigned to the leading edge and trailing edge subregions. The results show a high dependency on the sound source distribution and the source strength with regard to the observed one‐third octave bands, wind velocity, and blade geometry. Hence, the localization of rotating sound sources with a microphone array is a suitable method for the development of wind turbine blades that emit less noise.

Measuring noise from wind turbines is a problematic metrological task due to the significant interference caused by the wind, especially in the low-frequency range. In the audible band, especially A-weighted, the impact of interference from wind is considerably less than in the low-frequency and infrasound bands. In the audible band, especially the A-weighted curve, the impact of interference from wind is significantly less than in the low-frequency and infrasound bands. For this reason, methods are still being sought to reduce interference from wind in the lowest frequency bands effectively. Experimental tests within the scope of the work were carried out using several windshields, with a single standard windscreen at 1.5 m and 4 m height, with an additional microphone shield (tent), and on the board with a double windscreen at a ground level according to IEC 61400-11. Experimental verification of a windshield's effectiveness and impact under real conditions was carried out using a low-frequency noise source, which was the main fan station at the salt mine shaft. This source generates noise with similar spectral characteristics to wind turbines and can operate in windless conditions. This allowed noise measurements to be made without interference from the wind. Signals were recorded in windless and windy conditions at different wind speeds using tested windshields. An effectiveness analysis of the proposed measurement methods was also carried out on the wind farm. Performed research indicates that the best of the tested variants, when measuring wind turbine noise in the low-frequency range, is to place the microphone on the board with a double windscreen according to IEC 61400-11. At wind speeds of less than 5 m/s at 1.5 m above the ground, the shield effectively eliminates disturbances in the band above 4 Hz. Still, as the wind speed increases above 6 m/s, the level of disturbance increases, and its bandwidth in the lowest frequencies expands. [ABSTRACT FROM AUTHOR]

With the confidentiality of turbine blade geometry, wind farm developers and/or end-users have difficulties to optimize their wind turbine operations and wind farm layouts with respect to noise as existing sound source models rely on detailed blade geometry of wind turbines. This paper presents a new methodology of modeling wind turbine noise that does not need to access the details of blade geometry. The new methodology consists of two steps: First, the candidate wind turbine is approached by up/down scaling from a known wind turbine (for example the National Renewable Energy Laboratory 5 MW wind turbine) according to its operational conditions and limited data provided from the manufacturer; then a sound source model (for example Amiet's model) is applied to calculate the sound pressure level at needed positions. The developed methodology is validated against wind turbine noise measurements for a 4 MW wind turbine with unknown blade geometry; good agreement was found, with an averaged difference of 1.2 dB for various wind conditions under neutral, stable and unstable atmospheric thermostability. By combining with a sound propagation model, the new methodology can be used for designing and controlling wind farms. • A new methodology of modeling wind turbine noise is proposed for wind farm application. • The new method does not need to access the confidential blade geometry. • Up/down scaling technique is used to approach the candidate wind turbine. • Validations against field acoustic measurements are made for a 4 MW wind turbine. • The developed model has potential to be used for wind farm design application. [ABSTRACT FROM AUTHOR]

This paper presents an overview of the indices used in evaluating ILFN noise, based on C and G weighting curves and LC-LA difference parameter, as well as curves compared to the loudness threshold curve. The research section includes measurement results of wind turbine (WT) noise along with proposed indicators for evaluating this noise in the infrasound and low-frequency bands at distances of 250 m, 500 m and 1000 m from the turbine. The results obtained indicate low noise levels in the infrasound band, lower than the threshold curves from a dozen or so dB in the upper part of this band to nearly 60 dB in the lower part. The LC-LA indicator has been shown to be of poor utility for evaluating low-frequency noise, with the LG indicator reasonably useful for evaluating infrasound noise. [ABSTRACT FROM AUTHOR]

The operation of a wind turbine (WT) is characterized by fluctuations in sound pressure amplitude associated with the passage of the propeller blade through the tower. Amplitude Modulation (AM) is one of the factors that contributes to the increased annoyance of wind turbine noise. The phenomenon of AM is currently the subject of research in many research centers around the world in the context of a parametric assessment of its impact on annoyance. Despite the development of many methods to measure the AM of a WT noise, there is no commonly accepted method. This paper discusses the most crucial factors that stimulate the phenomenon of AM and the implementation in the MATLAB environment of the algorithm to find the frequency and depth of AM proposed by the Amplitude Modulation Working Group (AMWG). The results of verification of the developed algorithm as well as the measurement results of the frequency and depth of modulation for two measurement samples of a 2 MW wind turbine are presented. [ABSTRACT FROM AUTHOR]

Wind turbines (WT) can produce large amounts of energy and thus help economies make an important step towards a sustainable energy future. However, residents living near wind farms ascribe to wind turbine noise (WTN) a multitude of adverse health impacts and use them as an argument against wind farms. This paper reviews the relevant literature on the effects of wind turbine noise in order to help address the controversy that surrounds the safety of wind turbines and, in this way, to enhance community acceptance of wind farms. The objectives are to compare the findings of quantitative, experimental and longitudinal research on these effects and to detect whether findings are consistent. The analysis showed that while quantitative research recorded adverse health effects, experimental and longitudinal research provided no supporting evidence. However, findings from these different research types were consistent in indicating a risk for sleep posed by WTN. In addition, quantitative and experimental research converges that annoyance to WTN is affected by the visual impact of wind turbines on the landscape as well as attitudes to wind energy in general. Moreover, experimental work has shown that exposure to information on the Internet that accentuates negative health effects due to WTN can account for residents' complaints about adverse health effects. Finally, it is necessary to perform more longitudinal research on the health of residents in relation to WTN as well as more quantitative research on quality of life of individuals residing near wind farms. • Convergent quantitative, longitudinal and experimental findings show risk for sleep. • Wind energy attitudes and the visual impact of wind turbines affect noise annoyance. • Objective information can prevent the ascription of health effects to noise. • More longitudinal research on the health effects of wind turbine noise is needed. • Quality of life of residents exposed to wind turbine noise is understudied. [ABSTRACT FROM AUTHOR]

The operation of a wind turbine results in a series of pulses where there is a significant instantaneous increase in the amplitude of the pressure signal, dependent upon the wind speed at the turbine blades. The variations in the amplitude of the sound being emitted can be significant at receiver locations both as an audible and inaudible sound. The modulation of the A-weighted amplitude of the acoustic signature for wind turbines is often referred to as “amplitude modulation”. Criteria have been proposed in the UK to define “excessive amplitude modulation”. In a technical sense, the general descriptor for wind turbine amplitude modulation is incorrect. The correct term for the variation of the A-weighted level is modulation of the amplitude. The rate of the modulation of the dB(A) level occurs at the blade pass frequency, which is in the infrasound region. Turbines can exhibit amplitude modulation in the low frequency region. The differences between amplitude modulation and modulation of the amplitude occurring at an infrasound rate are discussed in the context for an environmental assessment of a wind farm with respect to permit conditions and a simplified method of assessment with respect to the Modulation Index.

Simple Summary: We analyzed the behavioral–physiological–immunological interconnected process of Japanese tree frogs (Dryophytes japonicus) during their breeding season when exposed to wind turbine noise. Frogs collected from paddy fields with wind power generators exhibited a faster call rate, higher salivary concentrations of corticosterone, and lower innate immunity. However, frogs exposed to the turbine noise for a short period of time only showed faster call rates. An increase in corticosterone was correlated with an increase in call rate and a decrease in immunity. It seems that the need for energy mobilization due to an increase in the call rate leads to a decrease in innate immunity through an increase in corticosterone. The decrease in immunity due to energy tradeoff or physiological response can change disease epidemiology in the population and create new adaptive patterns within these habitats. As the advantages of wind energy as an eco-friendly strategy for power generation continue to be revealed, the number of offshore wind farms also increases worldwide. However, wind turbines can induce behavioral and physiological responses in animals by emitting various types of noises. In this study, we investigated the behavioral, physiological, and immunological responses of male Japanese tree frogs (Dryophytes japonicus) when exposed to wind turbine noise. To determine the effects during the breeding season, frogs were collected from areas with and without wind turbines. Additionally, we exposed the frogs to recorded wind turbine noise at a site without a wind generator for 1 h to 24 h to analyze the short-term effects. Three types of calling patterns (dominant frequency, note duration, and call rate) were analyzed to investigate behavioral responses. Physiological responses were assessed using two steroid hormones assays, namely testosterone and corticosterone detection in the saliva. The immunity of each individual was assessed using a bacterial killing assay. The wind turbine group in the field had a higher call rate and corticosterone levels and lower immunity than the group in the field without turbines present, and all three of these variables were correlated with each other. Conversely, in the noise exposure experiment, a higher call rate was only observed post-exposure compared to pre-exposure. Thus, turbine noise seems to induce decreased immunity in Japanese tree frogs as an increase in energy investment that triggers a behavioral response rather than acting as a sole physiological response that leads to a direct increase in corticosterone. This decreased immunity due to energy tradeoff or physiological response can change the disease epidemiology of the population and create new adaptive patterns in these habitats. [ABSTRACT FROM AUTHOR]

In order to advance the expansion of onshore wind energy, wind turbines (WTs) must be erected in often complex terrain. The orography and the associated meteorological conditions, as well as the complex propagation of sound and ground motion waves can lead to increased annoyance of residents. Here a joint investigation of residential noise reports, meteorological, acoustic and ground motion data together with operational parameters of a wind farm in southern Germany is presented, with the objective to assess the annoyance of residents affected by WT emissions. Once strongly annoyed residents had been identified, simultaneous measurements were conducted over a 2-month period while residents used a noise reporting app to document their annoyance. A combination of the data shows that WT-related signals can be detected by acoustic and ground motion measurements in the vicinity of the WTs and, to a lesser extent, at the residential sites. In addition, background noise can be identified well. The app data indicates higher complaint rates in the early morning, evening and night hours. Changes in rotation rate seem to be the cause of annoyance as well as high rotation rates. These findings can be used to adjust WT operation in order to decrease immissions. [ABSTRACT FROM AUTHOR]

Amplitude modulation increases the annoyance caused by wind turbine noise. One gets the improved annoyance when a penalty is added to the measured or calculated time-average sound level. The amplitude modulated wind turbine noise consists of pulses. Each of them could be characterized by the short timeaverage sound level and the modulation depth. The latter determines the pulse penalty. This paper shows how to calculate the improved annoyance of amplitude modulated wind turbine noise, when the short time-average sound level and the penalty for each pulse are known. A special case of identical pulses is discussed. The proposed methodology needs to be tested by research. [ABSTRACT FROM AUTHOR]

An experimental investigation on scaled wind turbine models in a wind tunnel with a microphone array is presented. Our study focuses on the localization and quantification of aerodynamic noise sources on rotating wind turbine blades with the aim of identifying the contributing factors that have an impact on the source spectra. Therefore, wind tunnel measurements were conducted for three different blade geometries (NACA 4412 shape, Clark‐Y shape, and sickle shape), five pitch angles between −2° and +8° and five wind velocities between 5 and 13 mŝ−1. For the localization of rotating sound sources with a microphone array, a rotating beamforming method based on the acoustic ray method is used. The Clean‐SC deconvolution method was used to improve the resolution of the acoustic sources, and integrated spectra were calculated for the individual blades. The sound sources were localized at the wind turbine blades and assigned to the leading edge and trailing edge subregions. The results show a high dependency on the sound source distribution and the source strength with regard to the observed one‐third octave bands, wind velocity, and blade geometry. Hence, the localization of rotating sound sources with a microphone array is a suitable method for the development of wind turbine blades that emit less noise. [ABSTRACT FROM AUTHOR]

This review is focussed on large-scale, horizontal-axis upwind turbines. Vertical-axis turbines are not considered here as they are not sufficiently efficient to be deployed in the commercial generation of electricity. Recent developments in horizontal-axis wind turbine noise research are summarised and topics that are pertinent to the problem, but are yet to be investigated, are explored and suggestions for future research are offered. The major portion of recent and current research on wind turbine noise generation, propagation and its effects on people and animals is being undertaken by groups in Europe, UK, USA, Japan, Australia and New Zealand. Considerable progress has been made in understanding wind turbine noise generation and propagation as well as the effect of wind farm noise on people, birds and animals. However, much remains to be done to answer many of the questions for which answers are still uncertain. In addition to community concerns about the effect of wind farm noise on people and how best to regulate wind farm noise and check installed wind farms for compliance, there is considerable interest from turbine manufacturers in developing quieter rotors, with the intention of allowing wind farm installations to be closer to populated areas. The purpose of this paper is to summarise recent and current wind farm noise research work and the research questions that remain to be addressed or are in the process of being addressed. Topics that are the subject of on-going research are discussed briefly and references to recent and current work are included.

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.

Amplitude modulation (AM) is a common phenomenon associated with wind turbine (WT) related noise annoyance. Within the interdisciplinary project Inter-Wind, acoustic, ground motion, and meteorological data are captured to be evaluated with noise reports of residents living near a wind farm in Southern Germany. The recorded data builds a solid data base for the evaluation of AM. The occurrence of AM is detected within acoustic and ground motion data and set in relation to all available data, including WT operational parameters, meteorology, and noise reports. In this study, the origins of detected AM are tones at 57.8 Hz and 133 Hz, related to the generator and drive train, which are amplitude modulated by the blade passing frequency. AM detection was successful both with acoustic as well as ground motion data. A comparison of a method for AM detection developed by the Institute of Acoustics (IOA reference method) with a method specifically developed to detect AM in ground motion data showed that the reference method detected AM three to six times more often than the newly developed method. AM occurred most likely during stable atmospheric conditions, with a positive lapse rate, and was (albeit to a small degree) more likely to be detected when residents reported higher levels of annoyance.

Upon understanding the depletion of fossil fuels and their damage to the world, developed countries decided to produce energy from renewable energy sources. One of the most common methods of renewable energy sources is wind energy. One of the main problems in this matter is the noise generated by the turbine during operation. Prolonged exposure to noise causes both physical and mental distress. This study aims to examine different blade tip shapes in order to reduce wind turbine blade noise. In this study, a 12% scaled model of NREL Phase VI wind turbine has simulated, and analyzes have made using the CFD program. Large Eddy Simulation has been used as the turbulence method in the calculations, and FW-H equations have been preferred in the acoustic calculations. Basic blade, chamfer blade, and radius blade have been used in the calculations. The results obtained have been compared with the Korea Aerospace Research Institute (KARI) results at the low-speed wind tunnel. As a result, it has been observed that the wind turbine blade tip shape is an essential factor in noise. [ABSTRACT FROM AUTHOR]

Measuring noise from wind turbines is a problematic metrological task due to the significant interference caused by the wind, especially in the low-frequency range. In the audible band, especially A-weighted, the impact of interference from wind is considerably less than in the low-frequency and infrasound bands. In the audible band, especially the A-weighted curve, the impact of interference from wind is significantly less than in the low-frequency and infrasound bands. For this reason, methods are still being sought to reduce interference from wind in the lowest frequency bands effectively. Experimental tests within the scope of the work were carried out using several windshields, with a single standard windscreen at 1.5 m and 4 m height, with an additional microphone shield (tent), and on the board with a double windscreen at a ground level according to IEC 61400-11. Experimental verification of a windshield’s effectiveness and impact under real conditions was carried out using a low-frequency noise source, which was the main fan station at the salt mine shaft. This source generates noise with similar spectral characteristics to wind turbines and can operate in windless conditions. This allowed noise measurements to be made without interference from the wind. Signals were recorded in windless and windy conditions at different wind speeds using tested windshields. An effectiveness analysis of the proposed measurement methods was also carried out on the wind farm. Performed research indicates that the best of the tested variants, when measuring wind turbine noise in the low-frequency range, is to place the microphone on the board with a double windscreen according to IEC 61400-11. At wind speeds of less than 5 m/s at 1.5 m above the ground, the shield effectively eliminates disturbances in the band above 4 Hz. Still, as the wind speed increases above 6 m/s, the level of disturbance increases, and its bandwidth in the lowest frequencies expands.

Wind turbines play an important role in the worldwide mission of producing renewable energy. The development toward integrating large-scale wind turbines in the urban environment has raised concerns over the noise impacts on urban residents. While most of the existing studies on wind turbine noise (WTN) have focused on rural settings, this paper investigates the relationship between WTN, noise perception and self-reported health of people, and controlling for background characteristics of the residents in urbanized areas. Questionnaire surveys were carried out around three suburban wind farms in the UK with 359 respondents. A-weighted sound pressure levels of WTN were predicted using noise mapping, for the most exposed façade of each dwelling of the respondent. The dose-response relationship was found between WTN and annoyance, moderated by age and degree of education. WTN was associated with some aspects of self-reported health, including raised health concerns, having headaches, nausea, and ear discomfort, but was not related to sleep disturbance directly. Noise sensitivity, attitudes to wind energy, and visibility of the wind turbines were found to significantly influence self-reported health. By employing a second variant of the questionnaire with the research aim masked, this study also addressed the focusing effects induced by the questionnaire design. The significant differences in the reported adverse health between questionnaire variants implied focusing bias among the sample who knew the research purpose. This elicited a methodological finding that should be noted in future research.

Wind turbines play an important role in the worldwide mission of producing renewable energy. The development toward integrating large-scale wind turbines in the urban environment has raised concerns over the noise impacts on urban residents. While most of the existing studies on wind turbine noise (WTN) have focused on rural settings, this paper investigates the relationship between WTN, noise perception and self-reported health of people, and controlling for background characteristics of the residents in urbanized areas. Questionnaire surveys were carried out around three suburban wind farms in the UK with 359 respondents. A-weighted sound pressure levels of WTN were predicted using noise mapping, for the most exposed façade of each dwelling of the respondent. The dose-response relationship was found between WTN and annoyance, moderated by age and degree of education. WTN was associated with some aspects of self-reported health, including raised health concerns, having headaches, nausea, and ear discomfort, but was not related to sleep disturbance directly. Noise sensitivity, attitudes to wind energy, and visibility of the wind turbines were found to significantly influence self-reported health. By employing a second variant of the questionnaire with the research aim masked, this study also addressed the focusing effects induced by the questionnaire design. The significant differences in the reported adverse health between questionnaire variants implied focusing bias among the sample who knew the research purpose. This elicited a methodological finding that should be noted in future research. [ABSTRACT FROM AUTHOR]

Little is known about the potential impacts of wind turbine noise (WTN) on sleep. Previous research is limited to cross‐sectional studies reporting anecdotal impacts on sleep using inconsistent sleep metrics. This meta‐analysis sought to comprehensively review studies evaluating the impact of WTN using widely accepted and validated objective and subjective sleep assessments. Search terms included: "wind farm noise", "wind turbine noise", "wind turbine sound", "wind turbine noise exposure" AND "sleep". Only original articles published in English published after the year 2000 and reporting sleep outcomes in the presence of WTN using polysomnography, actigraphy or psychometrically validated sleep questionnaires were included. Uniform outcomes of the retrieved studies were meta‐analysed to examine WTN effects on objective and subjective sleep outcomes. Nine studies were eligible for review and five studies were meta‐analysed. Meta‐analyses (Hedges' g; 95% confidence interval [CI]) revealed no significant differences in objective sleep onset latency (0.03, 95% CI −0.34 to 0.41), total sleep time (−0.05, 95% CI −0.77 to 0.67), sleep efficiency (−0.25, 95% CI −0.71 to 0.22) or wake after sleep onset (1.25, 95% CI −2.00 to 4.50) in the presence versus absence of WTN (all p >.05). Subjective sleep estimates were not meta‐analysed because measurement outcomes were not sufficiently uniform for comparisons between studies. This systematic review and meta‐analysis suggests that WTN does not significantly impact key indicators of objective sleep. Cautious interpretation remains warranted given variable measurement methodologies, WTN interventions, limited sample sizes, and cross‐sectional study designs, where cause‐and‐effect relationships are uncertain. Well‐controlled experimental studies using ecologically valid WTN, objective and psychometrically validated sleep assessments are needed to provide conclusive evidence regarding WTN impacts on sleep. [ABSTRACT FROM AUTHOR]

Aerodynamic noise is a limitation for further exploitation of wind energy resources. As this type of noise is caused by the interaction of turbulent flow with the airframe, a detailed resolution of the flow is necessary to obtain an accurate prediction of the far-field noise. Computational fluid dynamic (CFD) solvers simulate the flow field but only at a high computational cost, which is much increased when the acoustic field is resolved. Therefore, wind turbine noise predictions using numerical approaches remain a challenge. This paper presents a methodology that couples (relatively fast) wind turbine CFD simulations using actuator lines with a fast turn-around noise prediction method. The flow field is simulated using actuator lines and large eddy simulations. The noise prediction method is based on the Amiet–Schlinker's theory for rotatory noise sources, considering leading- and trailing-edge noise as unique noise sources. A 2D panel code (XFOIL) calculates the sectional forces and boundary layer quantities. The resulting methodology for the noise prediction method is of high fidelity since the wind turbine geometry is accounted for in both flow and acoustics predictions. Results are compared with field measurements of a full-scale wind turbine for two operational conditions, validating the results of this research. [Display omitted] • This research couples actuator line with Amiet's method to predict wind turbine noise • The method calculates noise using instantaneous aerodynamic results at a low cost • Good agreement is obtained between predicted far-field noise and field measurements [ABSTRACT FROM AUTHOR]

Due to the increased expansion of wind turbines (WTs) in the last two decades, seismologists have recently observed an impact of disturbing signals at seismic stations. Ground vibrations generated by WTs perturb the seismic background noise level at seismological monitoring sites causing the performance and functional capability of a seismological network to be limited which leads a conflict between operators of WTs and seismological institutions. With regard to a conflict settlement, the research project MISS (Minderung der Störwirkung von Windenergieanlagen auf seismologische Stationen) was initiated to investigate in detail the seismic signals emitted by a WT in order to identify and discuss methods to reduce the disturbance impact on seismic stations. A part of this research project is presented in this study and deals with movement patterns of a WT tower, foundation and the immediate subsurface as well as the amplitude decay behavior of the seismic noise with increasing distances to the WT. For this purpose, short- and long-term measurements were conducted at a single WT of the "Bürgerwindpark A31 Hohe Mark" located in Heiden (NRW, Germany). First, the first four eigenfrequencies of the WT tower are identified at 0.3 Hz, 1.1 Hz, 3.25 Hz and 6.0 Hz using 1.5-h recordings of sensors that were installed in different heights on the inner wall of the tower. From the measurements, linear, elliptical and circular motion patterns could be observed at the tower. The results of the long-term measurements using 15 mobile seismic stations installed over 1 month in two circular arrays with distances of 100 and 200 m around the WT and two additional stations, one deployed on the foundation and one directly besides in the field, also show linear, elliptical and circular particle movements of the foundation and shallow underground. By correlating power spectral density (PSD) spectra and vertical displacements with the prevailing wind direction, it can be shown that at the eigenfrequencies 0.3, 3.25 and 6.0 Hz Rayleigh waves are radiated in crosswind direction from the WT. In downwind direction, the wave field is dominated by the Love wave type. In contrast, at 1.1 Hz, the dominating wave type emitted by the WT in crosswind direction is Love wave and in downwind direction mainly of the Rayleigh wave type. In order to estimate an amplitude decay relationship of the WT-induced seismic waves, a 1.5-h line-array measurement with 36 sensors installed 100–1000 m from the WT and a sensor spacing of 25 m was used to determine attenuation curves of ground motion velocities proportional to r−b, with r as the distance between sensor and WT and b as the decay parameter, for the four eigenfrequencies of the tower. The calculated b-values are increasing with frequency from 0.30 to 0.86. [ABSTRACT FROM AUTHOR]

Ground acoustic impedance is important in the prediction of sound propagation. In this paper, a new measurement technique is developed based on the Image Source method. Two set-ups are used. Set-up 1 consists of a speaker at a height of 0.5 m and two microphones at heights of 0.2 m (or 0.3 m) and 0.5 m with a separation distance of 1.75 m between the speaker and microphones. Set-up 2 has a double separation distance and almost double heights of 0.5 m and 1 m. The impedance measurements were performed at grass-ground and soft soil-ground after harvest in two different wind farms in Denmark. The findings are: (1) The Nordtest method works in Set-up 1, but gives inconsistent results in Set-up 2. (2) The new method gives consistent results in both set-ups. (3) The flow resistivity obtained with an impedance model can only be used with that specific impedance model, and it becomes inaccurate when used with other impedance models. (4) The determination procedure of flow resistivity is suggested to work with any impedance model. (5) A relation between the flow resistivity obtained with the one-parameter model of Delany and Bazley and that obtained with the four-parameter model of Attenborough is derived. ∙ The Nordtest method works in Set-up 1 and gives inconsistent results in Set-up 2. ∙ The Image Source method gives consistent results in all set-ups. ∙ A flow resistivity obtained with an impedance model is inaccurate for other models. ∙ A determination procedure is proposed to work with any impedance model. ∙ A relation of flow resistivity obtained with two impedance models is derived. [ABSTRACT FROM AUTHOR]

As the advantages of wind energy as an eco-friendly strategy for power generation continue to be revealed, the number of offshore wind farms also increases worldwide. However, wind turbines can induce behavioral and physiological responses in animals by emitting various types of noises. In this study, we investigated the behavioral, physiological, and immunological responses of male Japanese tree frogs (Dryophytes japonicus) when exposed to wind turbine noise. To determine the effects during the breeding season, frogs were collected from areas with and without wind turbines. Additionally, we exposed the frogs to recorded wind turbine noise at a site without a wind generator for 1 h to 24 h to analyze the short-term effects. Three types of calling patterns (dominant frequency, note duration, and call rate) were analyzed to investigate behavioral responses. Physiological responses were assessed using two steroid hormones assays, namely testosterone and corticosterone detection in the saliva. The immunity of each individual was assessed using a bacterial killing assay. The wind turbine group in the field had a higher call rate and corticosterone levels and lower immunity than the group in the field without turbines present, and all three of these variables were correlated with each other. Conversely, in the noise exposure experiment, a higher call rate was only observed post-exposure compared to pre-exposure. Thus, turbine noise seems to induce decreased immunity in Japanese tree frogs as an increase in energy investment that triggers a behavioral response rather than acting as a sole physiological response that leads to a direct increase in corticosterone. This decreased immunity due to energy tradeoff or physiological response can change the disease epidemiology of the population and create new adaptive patterns in these habitats.

The specific working conditions of the wind turbine in strong wind cause a number of problems in the measurement of noise indicators used in its short and long-term assessment. The wind is a natural working environment of the turbine, but it also affects the measurement system, moreover, it can be a secondary source of other sounds that interfere with the measurement. One of the effective methods of eliminating the direct impact of wind on the measurement system is placing the microphone on the measurement board at ground level. However, the obtained result can not be directly compared with the admissible values, as it has to be converted to a result at a height of 4 m. The results of previous studies show that this relation depends, inter alia, on the speed and direction of the wind. The paper contains the results of measurements on the measurement board, according to EN 61400-11:2013, and at a height of 4 m above ground made simultaneously in three points around the 2 MW turbine at various instantaneous speeds and changing wind directions. Analysis of the impact of measuring point location on the measurement result of noise indicators and the occurrence of additional features affecting the relationship between the values measured on the board and at the height of 4 m, and especially the tonality, amplitude modulation and content of low frequency content, was made. [ABSTRACT FROM AUTHOR]

Il rumore è fra le maggiori fonti di disturbo ai cittadini risedenti nelle vicinanze di turbine eoliche. Indicatori di impatto semplici e affidabili sono di notevole interesse in fase di pianificazione territoriale, di autorizzazione e per l'informazione al pubblico. Si riporta lo studio di un indicatore di degrado acustico che consideri la variazione dei livelli di rumore ed il disturbo arrecato ai residenti (DALY e annoyance). L'indicatore è stato sperimentato sui 10 siti utilizzando il modello ISO 9613-2 e NORD2000. L'indicatore permette di valutare il degrado acustico derivante da scelte pianificatorie e può fornire un'immediata informazione al pubblico. ------ Wind turbine noise causes annoyance for citizens. Summarizing the relevant information with simple and reliable impact indicators is of remarkable interest during planning, authorization process and for public information. The present work shows the results in the development of a sound degradation indicator taking into account the change in noise levels and the disturbance to residents (DALY and annoyance). The indicator was tested on 10 wind sites using the ISO 9613-2 and NORD2000 noise models. The indicator developed enables to assess the possible sound degradation resulting from various planning decisions and resulted to be a useful tool to provide immediate information to the public.

Aims: In addition to the noise, sleep disturbance (SD) as an outcome of the exposure to the wind turbine noises (WTNs) can adversely affect general health. This study aimed to investigate the effect of SD induced from WTNs on general health indicators. Materials and Methods: A total number of fifty tree workers from Manjil wind farm voluntarily participated in this study. Based on the job similarity and vicinity to the sound sources, workers were classified into three occupational groups including repairman, security, and official staff. Individual's health and sleep status were gathered using the 28-item General Health Questionnaire and Epworth Sleepiness Scales, respectively. Noise was measured based on ISO 9612. ANOVA, Chi-square, and linear and multiple regression tests were used for data analysis in the SPSS 20 software environment. Results: The mean values of 8-h equivalent continuous A-weighted sound pressure level (LAeq, 8 h) among whole workers was 71 ± 10 dB (A). The averages of somatic symptom, anxiety insomnia, social dysfunction, depression, and general health among the participants were 5 ± 2.44, 7 ± 2.35, 11 ± 2.65, 2 ± 1.54, 22 ± 6.53, and 7.3 ± 3.1, respectively. According to the results, SD and noise exposure had an adverse health effect on physical symptoms, depression, and overall general health of participants. Moreover, SD and work experience were effective factors on anxiety-insomnia. SD had greatest effect on general health when all variables are controlled, so that general health will increase by 2.42 units for each unit increase of SD. Conclusion: We found that in addition to the sound effect, noise-induced SD also affects worker's health and strengthen sound effects on human well-being.

Several noise propagation models used to calculate the noise produced by wind turbines have been reported. However, these models do not accurately predict sound pressure levels. Most of them have been developed to estimate the noise produced by industries, in which wind speeds are less than 5 m/s, and conditions favor its spread. To date, very few models can be applied to evaluate the propagation of sound from wind turbines and most of these yield inaccurate results. This study presents a comparison between noise levels that were estimated using the prediction method established in ISO 9613 Part 2 and measured levels of noise from wind turbines that are part of a wind farm currently in operation. Differences of up to 56.5 dBZ, with a median of 29.6 dBZ, were found between the estimated sound pressure levels and measured levels. The residual sound pressure levels given by standard ISO 9613 Part 2 for the wind turbines is larger for high frequencies than those for low frequencies. When the wide band equivalent continuous sound pressure level is expressed in dBA, the residual varies between −4.4 dBA and 37.7 dBA, with a median of 20.5 dBA.

In recent years, the impact of wind turbines (WTs) on seismological stations has been noticed, since WT-induced ground motions perturbed the seismic background noise level at seismological monitoring sites. The resulting deterioration of the recording quality at seismic stations leads to a conflict between seismological network and WT operators. As a first step towards the solution of the conflict - or at least a peaceful coexistence - it is of paramount importance to understand the characteristics of seismic signals generated by WTs. For this study, a 6.5-week measurement campaign was conducted at a wind park (WP) consisting of five 2 MW turbines in North Rhine-Westphalia (Germany) with eleven mobile seismic stations installed at distances of 1–10 km from the WP. At each measurement point, power spectral density (PSD) spectra are calculated and correlated with different operating states of the WTs. Changes in the operating states of the WT are reflected in the noise level at the seismic stations with different distances to the WP. An analysis of the radiated frequencies from the WT foundation into the subsurface is carried out by performing shutdown and switch-on tests at the WP. In this way, seismic signals generated by WTs are identified and used to illustrate how frequency-dependent peaks in WT-induced seismic noise are attenuated with distance. The attenuation of the peaks can be described by a power-law decay proportional to r−b, with r as the distance between station and WT and b as the decay parameter with values between 2.4 and 5.5. The relationship between the noise level at a seismic station and the number of WTs in operation, that behave as interacting sources for the background noise level, could be determined as ∼ N , with N being the number of switched-on WTs. [ABSTRACT FROM AUTHOR]

Noise, emitted by wind turbines, is one of the main health risk factors which has been recently considered in many researches. Noise annoyance is among the most important human responses to noise. The aim of this work was to modeling of annoyance due to noise at workplace coming from wind turbines in workers. All workers of a wind power plant consisted the study sample. The equivalent noise level was measured using a task-based method. Moreover, data related to noise annoyance and noise sensitivity were acquired by standardized methods. Based on the results, noise exposure, noise sensitivity, visibility, age, and experience affected noise annoyance. According to path analysis, the most indirect and direct effect on noise annoyance were attributed to noise exposure. Age, sensitivity, and noise exposure were positively associated to annoyance. It can be concluded that there is a significant relationship between age, experience, sensitivity to noise, and exposure to the wind turbine noise with noise annoyance. [ABSTRACT FROM AUTHOR]

Highlights • Acoustical and visual characteristics are both associated with noise annoyance. • Wind turbine visibility increases noise annoyance. • Serial position effects modify audio-visual effects on annoyance. • Presentation order of audio-visual simulations should be considered carefully. Abstract Noise annoyance reactions in the population due to wind farms are related to visual as well as noise-related impacts of the farms. Improved understanding of these effects may support the planning of better accepted wind farms. Recently, tools for visualization and auralization of wind farms have been developed that allow mutually studying audio-visual effects on annoyance. The objective of this study was to investigate the audio-visual effects of different wind turbine noise situations on short-term noise annoyance in a psychophysical laboratory experiment, considering serial position effects (simple order and differential carryover effects). A set of 24 audio-visual situations covering a range of acoustical characteristics (sound pressure level, periodic amplitude modulation) and visual settings (landscape with visible wind turbine, landscape only, grey background) was created. The factorial design of the experiment allowed separating audio-visual effects from serial position effects on noise annoyance. Both visual and acoustical characteristics were found to affect noise annoyance, besides the participants' attitude towards wind farms. Sound pressure level and amplitude modulation increased annoyance, the presence of a visualized landscape decreased annoyance, and the visibility of a wind turbine increased annoyance. While simple order effects could be eliminated by counterbalancing, the initial visual setting strongly affected the annoyance ratings of the subsequent settings. Due to this differential carryover effect, visual effects could be assessed reliably only as long as the participants saw the initial visual setting. Therefore, the presentation order of audio-visual stimuli should be carefully considered in experimental studies and in participatory landscape planning. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract Annoyance caused by wind turbine noise is assessed in terms of the A-weighted time average sound level. The amplitude modulation of a wind turbine, defined as the fluctuations in the noise level, increases the annoyance caused. There are two types of modulation: normal (in close proximity to the turbine) and abnormal (at a distance from the turbine). The latter is perceived as very annoying thumps. To determine the noise level of thumps, the standard simulations divide the noise source (turbine blades) into hundreds of segments. Then, taking refraction and other wave phenomena into account, the segment contributions to the sound level at the receiver are estimated. These steps are repeated for all the blade segments at each angular position of the blade. In the present study, a simple phenomenological model of noise generation and propagation is proposed. It is based on the finding that the blade tips are the major contributors to the sound power of a wind turbine. Since the abnormal modulation of wind turbine noise is heard at a long distance, refraction is taken into account for a special case of a low level jet. To apply the proposed model, two in situ noise measurements are required: within the fully insonified zone and within the partly insonified zone. Highlights • Wind turbine noise, abnormal amplitude modulation, thumps, refraction due to low level jet. [ABSTRACT FROM AUTHOR]

Abstract This paper describes the generation of blade–tower interaction (BTI) noise from upwind turbines and pylon-mounted fans using a combination of experimental and numerical means. An experimental rotor-rig was used in an anechoic chamber to obtain BTI acoustic data under controlled conditions. A computational model, based on the solution of the unsteady Reynolds Averaged Navier Stokes (URANS) equations and Curle's acoustic analogy, was used to describe the generation of fan and simplistic model of wind turbine BTI noise by the rotor-rig. For both the fan and model wind turbine case, the tower was found to be a more significant source of BTI noise than rotor blades. The acoustic waveforms for both turbine and fan are similar; however, in the case of the turbine, the blade contribution reinforces that from the tower, while in the case of a fan, there is some cancellation between the tower source and the blade source. This behavior can be explained by the unsteady aerodynamics occurring during BTI. [ABSTRACT FROM AUTHOR]

Abstract Wind turbine noise (WTN) increases the risk of WTN annoyance and self-reported sleep disturbance, which in turn can influence people's well-being. However, the sound level explains only a small fraction of WTN annoyance. The purpose of our study was to determine how acoustic and various non-acoustic variables are associated with WTN annoyance indoors, WTN annoyance outdoors, and sleep disturbance due to WTN. 318 permanent residents living within 2 km of the nearest wind turbine in three different areas of Finland responded to the questionnaire. The turbines were relatively large, within 3 and 5 megawatts. The explanatory models were developed using binary logistic regression. The models predicting WTN annoyance had the predictive strengths of 67% for indoor and 71% for outdoor WTN annoyance. The concern for health effects was the most important factor related to both WTN annoyance and sleep disturbance due to WTN. Other factors explaining WTN annoyance were area, noise sensitivity, and general attitude towards wind power as a form of energy production. Sound level explained also outdoor annoyance and sleep disturbance related to WTN. Furthermore, women were more annoyed indoors and reported more sleep disturbance due to WTN than men. We believe that the health concerns and WTN annoyance could be reduced by providing the residents with more fact-based information about wind power and more interactive and transparent communication concerning the planning and building processes. Highlights • The survey involved three Finnish wind power areas with 3–5 MW wind turbines (WT). • The concern of health influences explained the best WT noise annoyance. • Area, noise sensitivity, and energy attitude explained WT noise annoyance as well. • Health concern, sound level, noise sensitivity and gender predicted sleep problems. • Communicating fact-based information and benefits could decrease adverse impacts. [ABSTRACT FROM AUTHOR]