Wind Turbine Acoustics Michigan Conservative Energy Forum October 25, 2021
Here are some of my publications on wind turbine acoustics. Continuous research including work for the U.S. Department of Energy, Lawrence Berkley National Laboratory, and the Massachusetts Clean Energy Center. SAMPLE OF PUBLICATIONS – Regulating and predicting wind turbine sound in the U.S., Proceedings of Inter-Noise 2018, Chicago, Il, August 2018
– Methods for Assessing Background Sound Levels during Post-Construction Compliance Monitoring within a Community, Proceedings of the 6th International Meeting on Wind Turbine Noise 2015. – Wind Turbines and Health; A Critical Review of the Scientific Literature, Journal of Occupational and Environmental Medicine 56(11) 2014. – The Massachusetts research study on wind turbine acoustics - Methods and goals, Proceedings of NoiseCon14, Fort Lauderdale, Florida, 2014. – Prevalence of complaints related to wind turbine noise in northern New England, Proceedings of Meetings on Acoustics, Vol 19, 2013. – Winning Community Acceptance: Dispelling Myths and Promoting the Realities about Wind Power – Noise Impacts, AWEA New England Regional Wind Energy Summit, 2012, and AWEA Community Wind Working Group webinar, 2012.
– Improving predictions of wind turbine noise using PE modeling, Proceedings of the 2011 Institute of Noise Control Engineers NOISECON 2011. – Calculating Annualized Sound Levels for a Wind Farm, Proceeding of Meetings on Acoustics, Acoustical Society of America, Volume 9, 2010. – Propagation Modeling Parameters for Wind Power Projects, Sound & Vibration Magazine, Vol. 24 no. 12, December 2008. 5
I’d like to share some information with you on acoustics and issues specific to wind turbines. SUMMARY
• Introduction to acoustical concepts • Wind turbine sound characteristics • Regulation of wind turbine noise
• Mitigating wind turbine sound • Takeaways
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Introduction to Acoustical Concepts
Sound Levels Around You
Most wind turbine sound
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The average nighttime sound level (Leq8-hr) in agricultural communities is 41 dBA. Average Nighttime Sound Level by Land Category 70
Nighttime Leq (dBA)
60
50
40
30
20
Night Leq
Category Mean Leq
10
9
CHANGE IN SOUND PRESSURE LEVEL
Sound Pressure Level & Human Perception 10 dB
5 dB
Change of 10 dB in a broadband sound source is perceived as twice as loud or half as loud
Change of 5 dB in a broadband sound Every 5 dB decrease in source is considered clearly perceptible
sound level results in an Change 3 dB in a broadband sound ~80%ofincrease in setback 3 dB
0 dB
source is considered barely perceptible Change of less than 3 dB in a broadband sound source is generally considered not perceptible
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Frequency • Frequency is the rate at which sound fluctuates in time expressed in Hertz (Hz) or cycles per second • It is what humans perceive as pitch or tone • Range of sensitivity for the human ear is 20 Hz to 20,000 Hz • General Frequency Range Descriptions – – – – –
Below 20 Hz is considered infrasound and is generally inaudible Low Frequency Sound: 20 Hz to ~200 Hz Mid Frequency Sound: ~200 Hz to ~4,000 Hz High Frequency Sound: ~4,000 Hz to ~20,000 Hz Above 20,000 Hz is ultrasound which most people cannot hear
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Humans are most sensitive to frequencies between 500 Hz and 4,000 Hz.
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Human Hearing Response Curve
Sound Pressure Level (dB)
0
-20
-40
-60
Infrasound
Human Hearing Frequency Range
-80 1
10
20
100
500
1,000
4,000
Ultrasound
10,000 20,000
100,000
Frequency (Hz)
Note: Hearing response curve represents average young person without hearing impairment.
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Wind Turbine Sound Characteristics
Most wind turbine sound is in the lower frequencies where the wind turbine is less audible.
A-weighted Sound Power Level (dBA)
Most of the audible sound is in the mid frequencies 120 110 100 90 80 70
Weighted sound pow er
60
Unw eighted sound pow er
50 40 20
.5 31
50
80
5 12
0 20
5 31
0 50
0 80
50 12
00 20
50 31
00 50
00 80
1/3 Octave Band Center Frequency
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Wind turbines generate infrasound, but at levels below human perception • Some wind turbines had distinctive low-frequency prominences, presumably from gearboxes • Infrasound is below audibility thresholds 150
>9 m/s (T - On)
140
>9 m/s (T - Off)
Sound Pressure Level (dBZ)
130 120 110 100 90 80 70 60 50
Turbine on Turbine off
40 30
20 10 0
0.5
0.63
0.8
1
1.25
1.6
2
2.5
3.15
4
5
6.3
8
10
12.5
16
20
1/3 octave band center frequency (Hz)
RSG et al, 2016, Exterior, Mountainous Location 8B, 650 m downwind
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Level of audibility Is highly dependent on being in the home and if the windows are closed
Hear Turbines On Property? 100%
100%
60% 40%
24%
28%
80% 99%
76%
yes no
20%
15% <0.5
0.5-1
39%
37%
22%
60%
85% 72%
0%
80%
Hear Turbines In Home With Windows Closed?
1-3
Distance From Turbine
40% 20%
61%
63%
<0.5
0.5-1
97%
78%
yes no
0% 3-5
1-3
3-5
Distance From Turbine
Source: LBNL Public Acceptance of Wind Energy 1616
People’s response to wind turbine sound: Audibility Is Highly Objective, While Annoyance Is Subjective Like the project look Noise sensitivity Prior Attitude View of turbine from property Rotor tip speed Turbine hub height Rotor diameter Low frequency DNL correction Atmospheric stability Summer daytime background L50 Wind turbine SPL (L1h, max) Project Participation Number of project turbines Discrete project Dominant project White College Age Female
Annoyance
Audibility
Washed out colors indicate the variable is not statistically significant
-5
15
35
55
Variable Importance (AIC)
Source: Haac, et al 2019
75
95
115
1717
A study in New England found 78% of capacity have no noise complaints. 600
500
Capacity (MW)
400
75 percent of the complaints were from just three wind projects
300
78% 200
4%
100
10% 0 No Complaints
Some Complaints
8% Complaints, greater than state standards
In a separate study, overall, about 4% of those living within 2,000 feet respond with a serious noise complaint (Hessler & Hessler, 2011) *Kaliski, K., “Winning Community Acceptance: Dispelling Myths and Promoting the Realities about Wind Power – Noise Impacts,” AWEA Community Wind Working Group, 2012.
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Wind Turbines & Human Health Michigan Conservative Energy Forum October 25, 2021 Jeffrey M. Ellenbogen, MMSc, MD
Background
Education:
Wind Turbine Experience:
• • • •
• Mass DPH/DEP • Testimony • Medical evaluations (IMEs)
MD and MMSc Neurology residency Neurology fellowship Postdoctoral fellowship
Board certification: • Neurology • Sleep Medicine Scientific Experience: • Including sound and human health
The Potential Problem
Signals as potential sources influencing health: • Noise and vibration • Shadow (flicker)
Health topics addressed: • sleep disruption • Neurological • Cardiovascular • Respiratory • Pain • Headache • Seizures • etc.
Studies addressing potential health problems
• No support for Wind Turbine Syndrome • No support for flicker-related seizures • Handful of studies, most low or very-low quality, except Health Canada studies • “Health Canada” • largest, most rigorous, most comprehensive set of studies evaluating potential impact on human health from wind-turbine noise.
Health Canada DESIGN OF THE STUDY • “Community Noise and Health Study” • Conducted: 2012-2014 • Cross-sectional, exposureresponse design • Published: 2016 • >1200 people (Ontario & PEI) • Age 18-79 • Goal: examine potential relationships between wind turbine noise and health outcomes among people living near turbines • < 25 dBA to 46 dBA (<25 = control)
VARIABLES EXAMINED BY STUDY: • Sleep • Stress • Heart Disease; high BP • Headaches; chronic Pain • Asthma • Dizziness • Tinnitus • Annoyance • Slight elevation at highest level, but more to do with non-acoustic factors (e.g., fear) • Quality of Life
Health Canada Findings & Notable Caveats
Findings & conclusion
Note:
• No association between noise levels and health outcomes
• A-weighted and Cweighted sound levels were highly correlated with one another
Regulation of Wind Turbine Noise
Essentials for What Makes a Good Standard
• • • •
Relevance Repeatability Predictability Ease of implementation
NOISE STANDARDS
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Common Mistakes Made in Noise Ordinances • Borrowed language from other ordinances with no understanding about what they mean (“snowball effect”)
• Infrasound limits • “Not-to-exceed” ordinances being interpreted (or using) Lmax. Lmax should never be used in a wind turbine ordinance • Unspecific language
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The Foundation of Noise Standards
the level of the sound from the Sound Levels source of interest and the weighting applied to those levels
the statistic that is used to describe Sound Metrics the sound how long the sound levels are Averaging Time measured Location where the sound is measured
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The Leq eq is the best metric for use in wind turbine noise regulation. • The IEC 61400-11 and -14 standards for specifying wind turbine sound output is Leq-based • The ISO 9613-2 standard for outdoor sound propagation predictions is Leq-based
• Studies on the long-term impacts of sound are Leqbased • The Leq weights periods with higher sound levels • The turbine-only Leq can be calculated by subtracting out background sound mathematically 29 20
Metrics are not interchangeable. • Going from one metric to another can have a substantial impact on project feasibility, even though the “level” is unchanged
• For example, a common community noise guideline to protect against sleep disturbance is 45 dBA Leq (8-hours) and 60 dBA LFmax, a 15 dB difference just due to metric and averaging time
30
The longer the averaging time, up to one hour, the more predictable and reliable the standard. • One hour averaging times are the most accurate to predict • One hour averaging times are more consistent from measurement to measurement • Shorter averaging times are less easy to predict and have higher variation • Instantaneous maxima (like Lmax) cannot be reliably predicted, have high variation between measurements, and are unrelated to impact. • Lmax should not be used in sound standards for wind turbines 31
The sound level relates to the location where the standard is applied
• The noise limit should be related to a particular impact, and the measurement location should reflect that impact • Noise impacts and related noise level standards related to sleep disturbance should specify measurement locations next to the home
32
Use of sound levels, metrics, averaging time, location in an ordinance No wind turbines shall emit sound levels in excess of the following during operation: – 45 dBA Leq (1-hour) within 50 feet of a Non-Participating Residence – 50 dBA Leq (1-hour) within 50 feet of a Participating Residence
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Mitigating Wind Turbine Sound
Wind turbine noise can be mitigated both before and after construction. DURING PERMITTING
AFTER CONSTRUCTION
Proper Siting
Sound Isolation
Turbine Selection
Turbine Maintenance
Noise Reduced Operations
Serrated Trailing Edges Neighbor Agreements
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Fair permitting processes can improve community acceptance. 1
Tell the truth – Wind turbines make noise – Wind turbines can be audible
– Some people find them annoying 2
Be fair – Acknowledge differing points of view (listen and learn)
– Work with neighbors and developers to address concerns – Be transparent 3
Be consistent and fact-based –
Consider reputable research, and use qualified consultants and engineers 36
Takeaways
Takeaways • Wind turbines generate sound • Community acceptance of wind power is benefited by – well-written regulations – fair and transparent permitting practices based on facts
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Contacts Contact www.rsginc.com
Ken Kaliski SENIOR DIRECTOR
Ken.Kaliski@rsginc.com
Public Safety Considerations • Site Inspection – Risk Assessment - Variety & Frequency of Potential Events • Emergency Response Pre-planning • Staff Training & Equipment (hours & dollars) • Risk to Site Personnel, 1st Responders, Public