Resource Documents: Noise (607 items)
Also see NWW press release on noise
Documents presented here are not the product of nor are they necessarily endorsed by National Wind Watch. These resource documents are provided to assist anyone wishing to research the issue of industrial wind power and the impacts of its development. The information should be evaluated by each reader to come to their own conclusions about the many areas of debate.
Short-term nighttime wind turbine noise and cardiovascular events: A nationwide case-crossover study from Denmark
Author: Poulsen, Aslak Harbo; et al.
A B S T R A C T
Aims: The number of people exposed to wind turbine noise (WTN) is increasing. WTN is reported as more annoying than traffic noise at similar levels. Long-term exposure to traffic noise has consistently been associated with cardiovascular disease, whereas effects of short-term exposure are much less investigated due to little day-to-day variation of, e.g., road traffic noise. WTN varies considerably due to changing weather conditions allowing investigation of short-term effects of WTN on cardiovascular events.
Methods and results: We identified all hospitalisations and deaths from stroke (16,913 cases) and myocardial infarction (MI) (17,559 cases) among Danes exposed to WTN between 1982 and 2013. We applied a time-stratified, case-crossover design. Using detailed data on wind turbine type and hourly wind data at each wind turbine, we simulated mean nighttime outdoor (10–10,000 Hz) and nighttime low frequency (LF) indoor WTN (10–160 Hz) over the 4 days preceding diagnosis and reference days. For indoor LF WTN between 10 and 15 dB(A) and above 15 dB(A), odds ratios (ORs) for MI were 1.27 (95% confidence interval (CI): 0.97–1.67; cases=198) and 1.62 (95% CI: 0.76–3.45; cases=21), respectively, when compared to indoor LF WTN below 5 dB(A). For stroke, corresponding ORs were 1.17 (95% CI: 0.95–1.69; cases=166) and 2.30 (95% CI: 0.96–5.50; cases=15). The elevated ORs above 15 dB(A) persisted across sensitivity analyses. When looking at specific lag times, noise exposure one day before MI events and three days before stroke events were associated with the highest ORs. For outdoor WTN at night, we observed both increased and decreased risk estimates.
Conclusion: This study did not provide conclusive evidence of an association between WTN and MI or stroke. It does however suggest that indoor LF WTN at night may trigger cardiovascular events, whereas these events seemed largely unaffected by nighttime outdoor WTN. These findings need reproduction, as they were based on few cases and may be due to chance.
Aslak Harbo Poulsen, Ole Raaschou-Nielsen, Alfredo Peña, Andrea N. Hahmann, Rikke Baastrup Nordsborg, Matthias Ketzel, Jørgen Brandt, Mette Sørensen
Diet, Genes and Environment, Danish Cancer Society Research Center, Copenhagen; DTU Wind Energy, Technical University of Denmark, Roskilde; and Department of Environmental Science, Aarhus University, Roskilde, Denmark
Environment International 114 (2018) 160–166. doi: 10.1016/j.envint.2018.02.030
Download original document: “Short-term nighttime wind turbine noise and cardiovascular events: A nationwide case-crossover study from Denmark”
There’s a Persistent Hum in This Canadian City, and No One Knows Why
Author: Mele, Christopher
A persistent noise of unknown origin, sometimes compared to a truck idling or distant thunder, has bedeviled a Canadian city for years, damaging people’s health and quality of life, numerous residents say.
Those who hear it have compared it to a fleet of diesel engines idling next to your home or the pulsation of a subwoofer at a concert. Others report it rattling their windows and spooking their pets.
Known as the Windsor Hum, this sound in Windsor, Ontario, near Detroit, is unpredictable in its duration, timing and intensity, making it all the more maddening for those affected.
“You know how you hear of people who have gone out to secluded places to get away from certain sounds or noises and the like?” Sabrina Wiese posted in a private Facebook group dedicated to finding the source of the noise.
“I’ve wanted to do that many times in the past year or so because it has gotten so bad,” she wrote. “Imagine having to flee all you know and love just to have a chance to hear nothing humming in your head for hours on end.”
Since reports of it surfaced in 2011, the hum has been studied by the Canadian government, the University of Western Ontario and the University of Windsor.
Activists have done their own sleuthing.
Over six years, Mike Provost of Windsor, who helps run the Facebook page, has amassed more than 4,000 pages of daily observations about the duration, intensity and characteristics of the sound and the weather conditions at the time.
He has had to fend off skeptics and theorists who believe that the hum is related to secret tunneling, U.F.O.s or covert government operations, he said.
Mr. Provost, a retired insurance salesman, said his work was a blend of obsession and hobby. “I’ve got to keep going,” he said in a phone interview. “I’m not going to quit this.”
The hum is not limited to Windsor, a city of about 220,000 people on the Detroit River. Mr. Provost said he had received reports from McGregor, Ontario, 20 miles to the south, and from east of Cleveland, about 90 miles away.
Tracey Ramsey, a member of the Canadian House of Commons, said in a phone interview that she regularly gets calls from constituents about the health effects of the hum. Residents have complained of headaches, sleeplessness, irritability and depression, among other symptoms.
“It’s something they are desperate for an answer to,” she said.
Tracing the noise’s origins is complicated by who hears it, and when and where.
Tim Carpenter, a retired consulting engineer who specialized in geotechnical engineering and machine vibrations and is an administrator of the Facebook page, says not everyone can hear it.
“It’s as if you had a fire hose moving back and forth and the people who have the water falling on them hear the noise, and if you’re outside that stream, you don’t hear the noise,” he said.
Researchers have found no trends related to gender or age for the “hearers.”
Dr. Darius Kohan, the director of otology and neurotology at Lenox Hill Hospital and Manhattan Eye, Ear and Throat Hospital, said that the low-frequency hum was unlikely to cause long-term hearing damage but that it could be as debilitating as tinnitus, a persistent ringing in the ears.
Scott Barton, an assistant professor of music at Worcester Polytechnic Institute in Massachusetts, said in a phone interview that infrasound, which is below 20 hertz, can create a sense of unease because it is unintelligible to human hearing but still detectable. While it is possible to be accustomed to certain noises (the hum of an air-conditioner, for example), this low-frequency noise is challenging because it has been so inconsistent, he said.
Seeking intervention by government regulators for the hum is difficult because regulations typically address decibel levels that can lead to hearing loss or damage, not those that can affect quality of life, Rebecca Smith, a sound engineer and doctoral student at the University of Michigan in Ann Arbor, who researches urban noise, wrote in an email.
“Think about the sound of a dog barking,” she said. “It doesn’t need to be loud enough to physically damage you to be really annoying and distracting.”
The University of Windsor report said the hum’s likely source was blast furnace operations on Zug Island on the Detroit River, which is densely packed with manufacturing. Activists complained that United States Steel, which operates the furnaces, has been uncooperative and secretive. A company spokeswoman did not respond to requests for comment.
A principal investigator on the study, Professor Colin Novak, told CBC News in 2014 that researchers needed more time and cooperation from the American authorities to pinpoint the source. “It’s like chasing a ghost,” he said.
Hums similar to Windsor’s have been reported in at least a dozen communities worldwide, including in Australia, England and Scotland, the study said. In the United States, high-profile hums have been reported in Taos, N.M., and Kokomo, Ind.
Researchers studied the Taos hum in 1993 but did not pinpoint a source. Karina Armijo, the town’s director of marketing and tourism, said in a telephone interview that complaints had subsided.
“I have never heard the Taos hum, but I’ve heard stories of the Taos hum,” she said. “There’s not been a lot of buzz about it in the last few years.”
A 2003 study in Kokomo by the acoustics and vibration consulting company Acentech prompted two industrial plants to install silencing equipment, providing relief to some residents but not all, a 2008 paper about the study said.
“In fact, one affected resident had become so disturbed that she moved more than 700 miles away to relieve her symptoms,” it said.
Mr. Carpenter said it was possible a major source of the Windsor hum could be eliminated and other mechanical sources would replace it, entering the “heard spectrum.”
“It’s possible that no matter what is done to relieve or attenuate the noise, it might never be enough,” he said.
—Christopher Meele, New York Times, Feb. 19, 2018
[NWW note: This story is reproduced here because the complaints are the same that many neighbors of large wind turbines make, and here they – as well as the physiologic effects of infrasound and low-frequency noise and the intrusive nature of pulsing noise (amplitude modulation), even at relatively low levels – are taken seriously. It might also be noted that across Lake St. Clair from Windsor there are hundreds of large wind turbines.]
Understanding stress effects of wind turbine noise – the integrated approach
Author: Pohl, Johannes; Gabriel, Joachim; and Hübner, Gundula
To better understand causes and effects of wind turbine (WT) noise, this study combined the methodology of stress psychology with noise measurement to an integrated approach. In this longitudinal study, residents of a wind farm in Lower Saxony were interviewed on two occasions (2012, 2014) and given the opportunity to use audio equipment to record annoying noise. On average, both the wind farm and road traffic were somewhat annoying. More residents complained about physical and psychological symptoms due to traffic noise (16%) than to WT noise (10%, two years later 7%). Noise annoyance was minimally correlated with distance to the closest WT and sound pressure level, but moderately correlated with fair planning. The acoustic analysis identified amplitude-modulated noise as a major cause of the complaints. The planning and construction process has proven to be central − it is recommended to make this process as positive as possible. It is promising to develop the research approach in order to study the psychological and acoustic causes of WT noise annoyance even more closely. To further analysis of amplitude modulation we recommend longitudinal measurements in several wind farms to increase the data base ─ in the sense of “Homo sapiens monitoring”.
Johannes Pohl, Joachim Gabriel, and Gundula Hübner
Institute of Psychology (J.P.), Martin-Luther-University Halle-Wittenberg, Halle (Saale); MSH Medical School Hamburg (J.P., G.H.), Hamburg; and UL DEWI (UL International GmbH) (J.G.), Wilhelmshaven, Germany
Energy Policy 112 (2018) 119–128
doi: 10.1016/j.enpol.2017.10.007
Download original document: “Understanding stress effects of wind turbine noise – the integrated approach”
[NWW note: The researchers note that their findings suggest that German emission protection laws are generally effective in establishing adequate setbacks. For “general” residential areas, the noise limit is 40dBA outside at night. For “purely” residential areas, spas, nursing homes, and hospitals it is 35dBA.]
Infrasound and low-frequency noise – does it affect human health?
Author: Alves-Pereira, Marian; Bakker, Huub; Rapley, Bruce; and Summers, Rachel
On the Engineers Ireland website, a search for ‘infrasound’ or ‘low-frequency noise’ yields zero results. A search on ‘noise’, however, yields 44 results. Why is it that infrasound and low frequency noise (ILFN) is still such a taboo subject? While it is improbable that this particular question will be answered here, an exposé of ILFN will be provided with a brief historical account of how and why ILFN was ultimately deemed irrelevant for human health concerns.
Infrasound and low-frequency noise (ILFN) are airborne pressure waves that occur at frequencies ≤ 200 Hz. These may, or may not, be felt or heard by human beings. In order to clarify concepts, in this report the following definitions are used:
- Acoustic phenomena: airborne pressure waves that may or may not be perceived by humans;
- Sound: acoustic phenomena that can be captured and perceived by the human ear;
- Noise: sound that is deemed undesirable;
- Vibration: implies a solid-to-solid transmission of energy.
In the early part of the 20th century, Harvey Fletcher of the Western Electrics Laboratories of AT&T, was tasked with improving the quality of reception in the telephone. To generate the sounds in a telephone earpiece, he used an AC voltage and had some of his colleagues rate the loudness of the sound received compared to the quietest tone heard.
The company was already using a logarithmic scale to describe the power in an electrical cable and it made sense to rate the loudness of the sounds also on a logarithmic scale related to the quietest voltage that could just be heard.
Initially he called this metric a ‘sensation unit’ but later, to commemorate their founder Alexander Graham Bell, they renamed it the ‘Bel’. A tenth of a Bel became known as the deciBel, corrupted to decibel, which has stuck with the scientific community to this day.
Fletcher-Munson curves and the dBA metric
To address the problem of industrial noise in the early 20th century, measurement was essential, as was a metric. At that time, researchers were critically aware that the readings on a sound level meter did not represent how loud or intense the sound was with respect to the subject’s perception of hearing.
From a biomedical perspective, this concept of perception is subjective, and changes between individuals and over timescales from minutes to decades. These serious constraints notwithstanding, it was acknowledged that some average measure of loudness would have some value for medicine and public health.
Harvey continued his research with Wilden Munsen, one of his team, by varying the frequency of the electricity to give pure tones, to which it is understood 23 of his colleagues listened to different levels of loudness, again through a simple telephone earpiece. (It is assumed they all had good hearing). They were then asked to score the sounds for equal loudness to that generated by an alternating current at 1000 cycles per second.
The level of the sound of course depended on the voltage applied, which could be measured. It is important to note two significant constraints here: The sounds were ‘pure’ sine waves, which are not common in nature, and the headphones enclosed the ear of the subject. This is a very unnatural way to listen to a very unnatural sound.
The numerical results of this study are known as the Fletcher-Munsen Curves (Fig 1). The (logarithmic) units of these curves are known as ‘phons’ and the inverse of the 40 phon curve forms the basis of the A-frequency weighting scale used everywhere today (Fig 2).
A-Frequency weighting scale
The minimum pressure required for humans to perceive sound at 1000 Hz is considered to be 20 micropascal, or an intensity of 10−12 watts per square meter. This corresponds to 0 phon on Figure 1, and 0 dBA in Figure 2. For all its shortcomings, the A-weighting has endured for decades and has become the de facto standard for environmental noise measurement. But is the A-weighting sufficient for all circumstances?
The answer is an emphatic ‘No’. It relates to the perception of loudness, which heavily discounts all frequencies below 1000 Hz and ends at 20 Hz. This 20-Hz limit was a consequence of equipment limitations of the 1920s and 30s, but has remained as the lower limit of human hearing to this day. The assumption that harm from excessive noise exposure is directly related to the perception of loudness has also remained to this day.
Observe in Fig 2 that, at 10 Hz, there is a 70-dB difference between what is measured and what is, de facto, present in the environment. In other words, three-and-a-half orders of magnitude of energy are discounted at this frequency.
The implications for public health are considerable, and within this line of reasoning, any event below 20 Hz becomes of no consequence whatsoever – and more so because it is not implicated in the classical effects of excessive noise exposure: hearing loss.
There are also issues of time and frequency resolution. Acoustic phenomena are time-varying events. A 10-minute average of acoustic events can hide more than it reveals. Similarly, segmenting frequencies into octave or 1/3-octave bands for analysis can also hide much that needs to be seen.
Today, affordable and highly portable equipment can record acoustical environments, and allow for post-analysis in sub-second time increments and 1/36-octave resolution. Waveform analysis from the sound file directly can achieve an even better resolution.
Field studies in Ireland
The following results, recently obtained in field-studies conducted in Ireland (July-November 2017), show why such resolution is needed to understand ILFN-rich environments. The classical metric (in dBA, 10-min averages and 1/3-octave bands) will be contrasted with what is needed for human health-related concerns (in dB with no frequency weighting, and resolutions of 0.2s and 1/36-octave bands), and not merely compliance with regulations.
Equipment and methods
Acoustical environments were recorded with a SAM Scribe FS recording system, a 2-channel recorder with sampling rates up to 44.1 kHz at 16-bit resolution and linear response down to almost 0.1 Hz [4-6]. Recordings were saved as uncompressed WAV files including the 1000 Hz/94 dB reference calibration tone prior to and after measurements. Windshields were placed on both microphones during the entire measurement sessions. Microphones were attached to tripods at approximately 1.5 m above the ground.
Location
Five homes located around the same industrial wind turbine (IWT) development have been the object of study. The data presented here refers to Home 1 (Fig 3). Table 1 shows the dates and times of all recordings that have been made to date in this home. The recordings selected for analysis and presentation herein were chosen on their educational value.
Table 1: Dates and times of recordings
| Home No. | Date | Time | Blue Channel | Red Channel |
| 1 | 04 Jul | 04:05–06:48 | In child’s bedroom, 1 | In child’s bedroom, 2 |
| 05 Jul | 15:33–17:50 | |||
| 10 Oct | 17:40–18:43 |
Fig 3: Reconstruction using a Google Earth image and showing the relative position of Home 1 and each of the six industrial wind turbines
The information classically obtained with the dBA metric, 1/3-octave bands and 10-min averaging (on 10 October, 2017, at 18:30) is given in Figs 4 and 5. Weather conditions obtained from Met Éireann for the closest weather tower at this time were as follows: air temperature: 14°C, precipitation: 0.1 mm, mean sea-level pressure: 1006.0 hPa, wind speed: 5.1 m/s (10 kt), wind direction: southwest (200° az).
Results
The values obtained for the sound pressure level and 1/3-octave bands are seen in Figs 4 and 5. The overall dBA metric (red bars labelled ‘Tot’) reflects the sound that humans would hear if they were present in this environment.
The sound pressure level in dBLin metric (grey bars labelled ‘Tot’) reflect the amount of acoustic energy to which humans are concomitantly exposed. The growing discrepancy between the two can be seen as the frequency falls below 1000 Hz.
Fig 4: Data covers a 10-minute interval analysed between 0.5-4000 Hz, in 1/3-octave bands, as recorded in Home 1, on 10 October 2017, at 18:30 (red microphone, i.e. inside child’s bedroom-2). The red bars are A-weighted values, while the gray bars indicate the acoustic energy that is, de facto present, in dBLin. In this environment, the human being would perceive through the ear an overall A-weighted pressure-level of approximately 34 dBA (Tot – red bar), while being concomitantly exposed to an overall acoustic pressure-level of approximately 74 dBLin (Tot – grey bar).
Fig 5: Data covers a 10-minute interval analysed between 0.5-1000 Hz, in 1/3-octave bands, as recorded in Home 1, on 10 October 2017, at 18:30 (red microphone, i.e. inside child’s bedroom-2). The red bars are A-weighted values, while the gray bars indicate the acoustic energy that is, de facto present, in dBLin. In this environment, the human being would perceive through the ear an overall A-weighted pressure-level of approximately 26 dBA (Tot – red bar), while being simultaneously exposed to an overall acoustic pressure-level of approximately 74 dBLin (Tot – grey bar).
Figure 6 shows the sonogram corresponding to the same 10-min period. This visual representation of time- and frequency-varying acoustic events provides much more information than the classical approach (Figs 4 and 5).
Here, short-term events can be seen in the region of 20-50 Hz (Fig 6). Tonal components can be seen at 10 Hz and 20 Hz that are not steady in amplitude and may be amplitude modulated, i.e., where the amplitude of the pressure is not continuous and varies periodically with time. The 10-minute averages, used in almost all legislation, hide these variations and are representative only of tonal components that are essentially unvarying over the 10-minute period in question.
Fig 6: Sonogram that covers the same 10-minute interval (600 s) as in Figs 4 and 5 showing time-varying features. The colour-coded bar on the right indicates sound pressure level values in dB Linear (no weighting). The horizontal line seen at 20 Hz is not a continuous tone because over the 600 s, its pressure level (colour-coded data) varies. A strong (yellow) acoustic phenomenon can be seen to exist at 1.6 Hz and also at 0.8 Hz. Home 1: No weighting, 1/36 octave bands (0.5-1000 Hz), 0.2 s average – Red Channel
The periodogram (Fig 7) over the same 10 minutes shows that there are distinct tonal components that form a harmonic series. When IWTs are the source of ILFN, the rotating blades generate repeated pressure waves as each blade replaces the previous one at any position.
A harmonic series is formed with the ‘blade pass frequency’ as the fundamental frequency (0.8 Hz here). These harmonics constitute what is called the wind turbine signature [7], which is impossible to identify using the classical dBA, 1/3-octave, 10-minute averaging methodology.
Fig 7: Periodogram covering the same 10-minute interval (600 s) as in Figs 4-6, and analyzed between 0.5-1250 Hz. The blade pass frequency of the IWT is 0.8 Hz. Harmonics of this fundamental frequency are shown in the figure. Each frequency band composing the harmonic series has a well-defined peak, e.g., the horizontal line seen in Fig 7 at 20 Hz is represented here as a peak at 20 Hz.
Final thoughts
Health concerns associated with excessive exposure to ILFN in the workplace have been around since the industrial boom in the 1960s [8]. In recent years, however, residential neighbourhoods have also begun to be flooded with ILFN [9-14]. The family living in Home 1, for example, has abandoned their residence due to severe health deterioration in all family members.
Accredited acousticians cannot ascertain compliance levels for ILFN because there are none – the vast majority of regulations worldwide do not cover this part of the acoustic spectrum. Nevertheless, public health officials and agencies should fulfil their job descriptions by becoming aware of the limitations of current noise guidelines and regulations.
Alternatives exist to gather the acoustic information relevant to the protection of human populations, in both occupational and residential settings. Noise regulations and guidelines need urgent updating in order to appropriately reflect ILFN levels that are dangerous to human health.
Mariana Alves-Pereira
School of Economic Sciences and Organizations (ECEO), Lusófona University, Lisbon, Portugal
Huub Bakker
School of Engineering and Advanced Technology, Massey University, Palmerston North, New Zealand
Bruce Rapley
Atkinson & Rapley Consulting, Palmerston North, New Zealand
Rachel Summers
School of People, Environment and Planning, Massey University, Palmerston North, New Zealand
Engineers Journal, 25 January 2018
References:
[2] Wikicommons (2017). Fletcher-Munson Curves. https://commons.wikimedia.org/wiki/File:Lindos4.svg
[3] Dirac (2017). Dirac Delta Science & Engineering Encyclopedia, A-Weighting. http://diracdelta.co.uk/wp/noise-and-vibration/a-weighting/
[4] Atkinson & Rapley Consulting Ltd (2017). Specification sheet for the SAM Scribe FS Mk 1. www.smart-technologies.co.nz
[5] Primo Co, Ltd. (Tokyo, Japan) (2017). Specification sheet for the electret condenser microphone, custom-made, model EM246ASS’Y. http://www.primo.com.sg/japan-low-freq-micro
[6] Bakker HHC, Rapley BI, Summers SR, Alves-Pereira M, Dickinson PJ (2017). An affordable recording instrument for the acoustical characterisation of human environments. ICBEN 2017, Zurich, Switzerland, No. 3654, 12 pages.
[7] Cooper S (2014). The Results of an Acoustic Testing Program Cape Bridgewater Wind Farm. Prepared for Energy Pacific (Vic) Pty Ltd, Melbourne, Australia.
http://www.pacifichydro.com.au/files/2015/01/Cape-Bridgewater-Acoustic-Report.pdf
[8] Alves-Pereira M (1999). Noise-induced extra aural pathology. A review and commentary. Aviation, Space and Environmental Medicine, 70 (3, Suppl.): A7-A21.
[9] Torres R, Tirado G, Roman A, Ramirez R, Colon H, Araujo A, Pais F, Lopo Tuna JMC, Castelo Branco MSNAA, Alves-Pereira M, Castelo Branco NAA (2001). Vibroacoustic disease induced by long-term exposure to sonic booms. Internoise2001, The Hague, Holland, 2001: 1095-98. (ISBN: 9080655422)
[10] Araujo A, Alves-Pereira M, Joanaz de Melo J, Castelo Branco NAA (2004). Vibroacoustic disease in a ten-year-old male. Internoise2004. Prague, Czech Republic, 2004; No. 634, 7 pages. (ISBN: 80-01-03055-5)
[11] Alves-Pereira M, Castelo Branco, NAA (2007). In-home wind turbine noise is conducive to vibroacoustic disease. Second International Meeting on Wind Turbine Noise, Lyon, France, Sep 20-21, Paper No. 3, 11 pages.
[12] Castelo Branco NAA, Costa e Curto T, Mendes Jorge L, Cavaco Faísca J, Amaral Dias L, Oliveira P, Martins dos Santos J, Alves-Pereira M (2010). Family with wind turbines in close proximity to home: follow-up of the case presented in 2007. 14th International Meeting on Low Frequency Noise, Vibration and Its Control. Aalborg, Denmark, 9-11 June, 2010, 31-40.
[13] Lian J, Wang X, Zhang W, Ma B, Liu D (2017). Multi-source generation mechanisms for low frequency noise induced by flood discharge and energy dissipation from a high dam with a ski-jump type spillway. International Journal of Environmental Research and Public Health, 14 (12): 1482.
[14] Rapley BI, Bakker HHC, Alves-Pereira M, Summers SR (2017). Case Report: Cross-sensitisation to infrasound and low frequency noise. ICBEN 2017, Zurich, Switzerland (Paper No. 3872).
