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Wind Turbine Noise: International Congress on Acoustics

International Congress on Acoustics, Montréal, 2-7 June 2013
Journal of the Acoustical Society of America, Vol. 133, No. 5, Pt. 2, May 2013

Draft Acoustical Society of America policy on wind turbine noise, as voted by those present at the Wind Turbine Noise Subcommittee of the Panel on Public Policy, 5 June 2013, in Montréal:

Acoustic emissions and effects of wind turbines have been reported by individuals living near many of these facilities, and reported by some medical authorities, as a source of adverse health effects. There is also mounting evidence that continuous acoustic emissions can have negative effects on wildlife species and ecosystems. The Acoustical Society of America urges that methods for measuring and quantifying wind turbine acoustic emissions, particularly at very low frequencies, and guidelines for relating wind turbine sound descriptors to probabilities of adverse effects be developed to aid in wise wind energy planning. The adverse effects of wind turbine acoustic emissions should be investigated and fully addressed in an interdisciplinary manner. “Acoustic emissions” includes airborne and underwater, infrasound, and structure-borne sounds.

Session 3aNSa, 5 June 2013
Noise: ASA Committee on Standards, Engineering Acoustics, and Structural Acoustics and Vibration:
Wind Turbine Noise I

http://asadl.org/jasa/resource/1/jasman/v133/i5?&section=ica-2013-montreal&page=34 [1]

Nancy Timmerman, Paul Schomer, and Sheryl Grace, Cochairs

Invited Papers

Activities of the Acoustical Society of America’s subcommittee on wind turbine noise and some studies being done. [2] Nancy Timmerman (Nancy S. Timmerman, P.E., 25 Upton St., Boston, MA 02118, nstpe@hotmail.com)

This paper will document the activities of the Acoustical Society of America’s (ASA’s) subcommittee (of the Panel on Public Policy) on Wind Turbine Noise, including what technical committees are represented, what special sessions will be held in the future, and the goal to generate a policy statement on the topic. The author, who is Chair of this subcommittee, will also describe what other current studies are or have been done in Massachusetts (in the United States) and, if applicable, elsewhere.

Development of a real time compliance system for wind farms regulated by ambient-relative noise standards. [3] Michael Hankard (Hankard Environ., 211 East Verona Ave., Verona, WI 53593, mhankard@hankardinc.com)

Some noise level regulations in the United States require wind turbine farms to not exceed the ambient sound levels at nearby residences by more than a fixed amount. For the project discussed herein, compliance with such a regulation requires curtailment of turbine operations to some degree at times when turbine operations are at or near maximum, atmospheric conditions are conducive to sound propagation, and sound from other sources including vegetation rustle are at a minimum. Based on the analysis of months of timesynchronized sound, meteorological, and operations data, a system was developed to assess compliance on a real-time, ongoing basis. The primary element in the determination of compliance is the shape of the one-third octave band spectrum at the residence, augmented by ground and hub-height meteorological conditions, and wind farm operations information. Without the spectral filter, curtailment would need to take place under a broader array of meteorological conditions to ensure compliance, which would result in loss of power generation revenue. This paper will describe the data collection and analysis methods, the development of the spectral filter, and the results of field testing including both the partial and entire shut down of the wind farm.

Criteria for wind-turbine noise immissions. [4] George Hessler (Hessler Assoc., Inc., 3862 Clifton Manor Place, Ste. B, Haymarket, VA 20169, George@HesslerAssociates.com) and Paul Schomer (Schomer and Assoc., Inc., Champaign, IL)

Each of the two authors has developed recommended single, 24-h, constant wind turbine noise criterion; the criteria are constants because wind turbine noise is basically not adjustable. Hessler develops his criterion from his knowledge of how wind turbine noise is being regulated at the local, state, and national levels, from regulations in other countries, and from his extensive experience with numerous wind turbine projects. Schomer develops his recommended criterion on the basis of existing national and international standards; notably ISO 1996-Part 1 and ANSI/ASA S12.9 parts 4 and 5. Ultimately, Hessler comes up with a single, 24-h A-weighted average criterion of 40 dB, and Schomer comes up with a 24-h A-weighted average criterion of 39 dB. These two researchers have decidedly different backgrounds, different experience, and a slight difference in orientation towards the industry. Thus, it is remarkable that these two criteria, derived in such different ways result in nearly identical 24-h A-weighted criteria levels. Although there is essential agreement in immissions criterion, there are variables debated herein for both modeling wind turbine emissions and certifying such emissions at faroff receptors that could result in a 10 dBA difference in the actual immissions level.

Prevalence of complaints related to wind turbine noise in northern New England. [5] Kenneth Kaliski (RSG Inc., 55 Railroad Row, White River Junction, VT 05001, ken.kaliski@rsginc.com)

As of September 2012, there were a dozen large operating wind projects with a total capacity of approximately 565 MW in northern New England, with more coming online by the end of the year. This paper evaluates the prevalence of noise complaints to regulatory authorities from those wind projects. Where possible, the exposure of residences to wind turbine sound is calculated. Exposure is estimated through standard ISO 9613-2 modeling procedures. A comparison of the exposure of complainants and non-complainants is made with the goal of assessing the prevalence of complaints at various modeled sound levels.

Can wind-turbine sound that is below the threshold of hearing be heard? [6] Paul Schomer (Schomer and Assoc. Inc., 2117 Robert Dr., Champaign, IL 61821, schomer@SchomerAndAssociates.com)

This paper is geared toward wind-turbine sound, but it is really a simple variation on the basic concepts that this author used in the development of loudness-level-weighted sound exposure (Schomer et al., J. Acoust. Soc. Am. 110(5, Pt. 1), 2390–2397 (2001)] and of Rating Noise Curves (RNC) [Schomer, Noise Control Eng. J. 48(3), 85–96 (2000)], which are used in our Standard, ANSI/ASA S12.2 Criteria for evaluating room noise. The fundamental issue is: Can we hear slowly surging or pulsating sounds for which the LEQ spectrum is below the threshold of hearing, where “slowly” means that the pulses come at a rate that is no faster than about 4 pulses per second? The short answer is yes, and the longer answer is that this effect is a function of the spectral content and becomes more-and-more prominent as the spectral content goes lower-and-lower in the audible frequency range. So surging or pulsing sound that is primarily in the 16 or 31 Hz octave bands will show the greatest effect. This paper shows the applicability of these results to wind-turbine sound. Variation in the threshold of hearing at low frequencies is an additional factor that also is discussed in this paper.

Amplitude modulation of audible sounds by non-audible sounds: Understanding the effects of wind turbine noise. [7] Jeffery Lichtenhan and Alec Salt (Otolaryngology, Washington Univ. in St. Louis, 660 South Euclid, St. Louis, MO 63110, LichtenhanJ@ent. wustl.edu)

Our research has suggested a number of mechanisms by which low-frequency noise could bother individuals living near wind turbines: causing endolymphatic hydrops, exciting subconscious pathways, and amplitude modulation of audible sounds. Here we focus on the latter mechanism, amplitude modulation. We measured single-auditory-nerve fiber responses to probe tones at their characteristic frequency in cats. A 50 Hz tone, which did not cause an increase in spontaneous firing rate (i.e., was not audible to the fiber when presented alone) was used to amplitude modulate responses to the probe tone. We found that as probe frequency decreased, a lower level of the low-frequency non-audible tone was needed to achieve criterion amplitude modulation. In other words, low-frequencies that are coded in the cochlear apex require less low-frequency sound pressure level to be amplitude modulated as compared to higher-frequencies that are coded in the cochlear base. This finding was validated, and extended to lower frequencies, by amplitude modulating gross measures of onset-synchronous (compound action potentials) and phase-synchronous (auditory nerve overlapped waveforms) in guinea pigs. Our results suggest that that infrasound generated by wind turbines may cause amplitude modulation of audible sounds, which is often the basis for complaints from those living near wind turbines.

Generation of wind turbine noise signature for use in lab environment. [8] Aleks Zosuls (Biomedical Eng., Boston Univ., Boston, MA), R. Morgan Kelley (Mech. Eng., Boston Univ., 110 Cummington Mall, Boston, MA 02215, sgrace@bu.edu), David Mountain (Biomedical Eng., Boston Univ., Boston, MA), and Sheryl Grace (Mech. Eng., Boston Univ., Boston, MA)

The fact that wind turbines produce infrasound continues to draw attention and discussion. Some argue that while the infrasound level produced by wind turbines is quite low, it still may be affecting the vestibular system or the hearing system, particularly via activation of the outer hair cells. Others hypothesize that the infrasound may be inducing whole body, chest cavity, or other human organ resonance. In order to study these hypotheses, it is first necessary to be able to recreate the turbine noise signature in a lab environment. Thus, the goal of this work is to create an acoustic system that can produce low-level infrasound. The system requirements include low cost, high fidelity, and imperceptible structural coupling to the lab. In addition, the system must be able to produce a broadband spectrum as well as a single tone. Progress toward the design of this audio system is discussed in this paper.

Contributed Papers

Wind turbine sound prediction – The consequence of getting it wrong. [9] William K. Palmer (TRI-LEA-EM, 76 Sideroad 33-34 Saugeen, RR 5, Paisley, ON N0G2N0, Canada, trileaem@bmts.com)

The application to permit a wind turbine power development usually involves submission of a prediction for the sound level that will occur at residences, schools, places of worship, and elsewhere people gather for restorative rest. This paper uses the example of a wind power development, and follows iterations taken to finalize the sound level prediction. The paper provides quantitative information collected since the start up of the wind power development on measured sound levels and octave band distribution; and qualitative observations on the special characteristics of the sound. Actual observations are compared to the predictions. More importantly, the paper reviews the consequences self-reported in qualitative interviews by citizens living with the changed environment after four years of operation of the wind power development. Reported impacts included difficulty sleeping, loss of jobs, and changes to social relationships, caregiving, pursuit of hobbies, leisure, learning, and overall health. Changes in measured health outcomes are identified. Both the quantitative and qualitative findings justify revision of the permitting process.

Predicting underwater radiated noise levels due to the first offshore wind turbine installation in the United States. [10] Huikwan Kim, James H. Miller, and Gopu R. Potty (Ocean Eng., Univ. of Rhode Island, 215 South Ferry Road, Narragansett, RI 02882, hkkim524@my.uri.edu)

Noise generated by offshore impact pile driving radiates into the air, water, and sediment. Predicting noise levels around the support structures at sea is required to estimate the effects of the noise on marine life. Based on high demands developing renewable energy source, the United States will begin the first pile driving within one to two years. It is necessary to investigate acoustic impact using our previously verified coupled Finite Element (Commercial FE code Abaqus) and Monterey Miami Parabolic Equation (2D MMPE) models [J. Acoust. Soc. Am. 131(4), 3392 (2012)]. In the present study, we developed a new coupled FE-MMPE model for the identification of zone of injury due to offshore impact pile driving. FE analysis produced acoustic pressure outputs on the surface of the pile, which are used as a starting field for a long range 2D MMPE propagation model. It calculates transmission loss for N different azimuthal directions as function of distance from the location of piling with the inputs of corresponding bathymetry and sediment properties. We will present predicted zone of injury by connecting N different distances of equivalent level fishes may get permanent injury due to the first offshore wind farm installation in the United States.

Session 3pNSa, 5 June 2013
Noise: ASA Committee on Standards, Engineering Acoustics, and Structural Acoustics and Vibration:
Wind Turbine Noise II

http://asadl.org/jasa/resource/1/jasman/v133/i5?&section=ica-2013-montreal&page=39 [11]

Nancy Timmerman, Paul Schomer, and Sheryl Grace, Cochairs

Contributed Papers

Wind farm – Long term noise and vibration measurements. [12] Martin Meunier (Environment, SNC-Lavalin, 2271, boul. Fernand-Lafontaine, Longueuil, QC J4G2R7, Canada, martin.meunier@snclavalin.com)

Most of the energy produced in Quebec comes from renewable sources. The concept of wind energy emerged in the late 1990’s and has since become a complementary source of energy alongside hydroelectricity. Wind farms are generally seen as a good sustainable way to produce energy. However, they are not implemented without some impact on the environment. SNC-Lavalin Environment has performed many surveys in recent years for wind farm projects, including noise measurements both before and after their commissioning. This presentation will give an overview of one such project where long term noise and vibration measurements where conducted. Vibration measurements, as well as outdoor, indoor, and low frequencies noise measurements were completed both with and without the wind turbines in operation. Data will be presented showing different problems encountered in the analysis phase. For example, multiple intermittent and non-steady noise sources were present during measurement (wind turbines, car pass-bys, wind in the trees, human activities). Methods used to overcome these obstacles will be discussed (use of statistical parameters, linear regression), and the effect of the wind turbine operation on the noise level (including low frequencies) and vibration level will be presented.

RoBin: A one-man measurement system for standard acoustic emission measurement according to IEC 61400-11. [13] Daniel Vaucher de la Croix (ACOEM, 200 Chemin des Ormeaux, Limonest 69578, France, daniel. vaucherdelacroix@acoemgroup.com) and Timo Klaas (Wolfel Messsysteme, Höchberg, Germany)

Wind turbines are built at more and more locations—which makes their noise emission an important subject. The international standard IEC 61400-11 and the German Technische Richtlinie fur Windenergieanlagen, Teil of the FGW were set up in order to unify the evaluation of noise emission. Measurement of noise emission according to these standards is linked to formidable challenges, especially for the installation of testing equipment and evaluation of data. After a short reminder on the ISO 61400 standard, the proposed paper will discuss the details of operational constraints linked with on-site measurements and how modern communication technologies help in an easy system deployment and most efficient operation for the benefits of its users.

Building integrated wind turbines – A pilot study. [14] Ben Dymock (The Acoust. Group, Dept. of Urban Eng., London South Bank Univ., 12 Deans Close, Amersham HP6 6LW, United Kingdom, dymockb@lsbu.ac. uk) and Stephen Dance (The Acoust. Group, Dept. of Urban Eng., London South Bank Univ., London, United Kingdom)

The current planning guidance in London requires that all new or refurnished large buildings should include 20% renewables. As part of a study on urban wind a pilot investigation based on the building integrated wind turbines on the skyscraper Strata Tower in London will be monitored for acoustics, vibration, anemometry and electrical generation. Strata Tower is a 150 m building in an urban location with three 19 kWe turbines in a specially designed venturi housing. The effect of the wind turbines on residents, the local community, and the building structure will be assessed and reported.

Assessment of annoyance due to wind turbine noise. [15] Malgorzata Pawlaczyk-Luszczynska, Adam Dudarewicz, Kamil Zaborowski, Malgorzata Zamojska, and Malgorzata Waszkowska (Dept. of Physical Hazards, Nofer Inst. of Occupational Medicine, 8, Sw. Teresy str., Lodz 91-348, Poland, mpawlusz@imp.lodz.pl)

The overall aim of this study was to evaluate the perception and annoyance of noise from wind turbines in populated areas of Poland. The study group comprised 378 subjects. All subjects were interviewed using a questionnaire developed to enable evaluation of their living conditions, including prevalence of annoyance due to noise from wind turbines, and the selfassessment of physical health and well-being. In addition, current mental health status of respondents was assessed using Goldberg General Health Questionnaire GHQ-12. For areas where respondents lived, A-weighted sound pressure levels (SPLs) were calculated as the sum of the contributions from the wind power plants in the specific area. It has been shown that the wind turbine noise at the calculated A-weighted SPL of 30–50 dB was perceived as annoying outdoors by about one third of respondents, while indoors by one fifth of them. The proportions of the respondents annoyed by the wind turbine noise increased with increasing A-weighted sound pressure level. Subjects’ attitude to wind turbines in general and sensitivity to landscape littering was found to have significant impact on the perceived annoyance. Further studies are needed, including a larger number of respondents, before firm conclusions can be drawn.