S is for Sound: What is the difference between Sound and Noise and why does it matter?
A summary of the Town of Union's Findings Regarding Wind Turbine Noise Impacts
The findings regarding Wind Turbine noise begin on page five of the ordinance.
The definitions section of the ordinance (page 11) helps us to understand some of the terms used in relation to Wind Turbine Noise.
Sound: A fluctuation of air pressure which is propagated as a wave through air. (p.17)
Noise: any unwanted sound. Not all noise has to be excessively loud to represent an annoyance of interference. (p.15)
Let's take a closer look at these two words, Sound, and Noise.
The NIDCD—(one of the National Institutes of Health) defines sound this way:
"What is sound? Sound is a form of energy, just like electricity and light. Sound is made when air molecules vibrate and move in a pattern called waves, or sound waves. Think of when you clap your hands, or when you slam the car door shut. That action produces sound-waves, …" [source]
Sound energy also moves through any medium that can carry vibration, including water, solid objects, and even our bodies. Think of the feeling in your chest during a parade as the bass drummer gets closer. That's the feeling of sound waves passing through your body.
A decibel [dBA] is a measuring unit for sound and noise.
Let's take a closer look at decibels and the decibel scale.
According to the Columbia Electronic Encyclopedia, 2007, Columbia University Press:
"Noise intensity is measured in decibel units.
The decibel scale is logarithmic; each 10-decibel increase represents a tenfold increase in noise intensity.
Human perception of loudness also conforms to a logarithmic scale; a 10-decibel increase is perceived as roughly a doubling of loudness.
Thus, 30 decibels is 10 times more intense than 20 decibels and sounds twice as loud;
40 decibels is 100 times more intense than 20 and sounds 4 times as loud;
80 decibels is 1 million times more intense than 20 and sounds 64 times as loud.
Subjected to 45 decibels of noise, the average person cannot sleep. … "
Summary of the Town of Union Findings on Wind Turbine Noise
Large wind turbines are a significant sources of noise which, if improperly sited, can negatively impact the health of residents, particularly in areas of low background (ambient) noise. (p.5,1)
A maximum Sound Pressure Level (SPL) of of 35dBA or 5 dBA over the normal background noise is necessary to protect residents from the adverse health effects associated with large wind turbine noise. (p.5,b.)
According to wind turbine noise studies, few respondents were disturbed in their sleep by wind turbine noise at an SPL of less than 35 dBA, but at greater than 35 dBA, respondents were increasingly disturbed in their sleep from wind turbine noise. (p.6,5 [Pedersen 2008] and )
Wind turbine noise greater than 5 decibels over normal background noise increases the risk for adverse health effects because a change of 5 decibels is clearly noticeable. (p.6,6. [Kamperman and James 2008])
The 50 decibel limit (dBA) set forth by the state of Wisconsin is too high to provide adequate protection. (p.5, b)
Large wind turbines emit two types of noise. One is mechanical noise from interaction of the turbine parts themselves, and the other is aerodynamic noise from the blades passing through the air which can generate broadband noise, tonal noise, and low frequency noise. (p.5, 2.)
These three varieties of noise are present when a helicopter flies low over your house. You hear a dense roar (broadband), the distinct sound of the blades (tonal), and feel the thumping vibrations in your chest cavity, (low frequency). Wind turbines can also produce all of these noises at once.
Large wind turbines create a noise annoyance that can hinder physical and mental healing, and can cause negative heath effects which include sleep disturbance and disruption, stress, anxiety, fatigue, (p.6, 3 [Harry 2007]) the adverse health effects associated with sleep disturbance and depravation, psychological distress, depression, headaches, tinnitus [ringing in the ears], and hypertension.
Wind turbine noise can affect each person differently. Some people are unaffected by wind turbine noise, while others may develop health problems from the same noise.
At low frequencies, wind turbine noise may not be heard, but rather felt as a vibration. Medical research reported complaints from people who felt the noise from large wind turbines, similar to symptoms that can be associated with vibroacoustic disease. (p.6, 4. [Pedersen 2007]   [Kamperman and James 2008] [Pierpont 2007] [Harry 2007] [Leventhal 2007]
Studies show that prolonged exposure to wind turbine noise resulted in adverse health effects at SPLs below those from other sources of community noise, such as road traffic noise. Sound generated by wind turbines has particular characteristics and creates a different type of noise, having different health impacts than compared to urban, industrial, or commercial noise. (p.7,7.) [Pedersen 2003]  [Soysal 2007]
Living in a rural environment, in comparison with a suburban area, increases the risk of residents being impacted by noise from nearby large wind turbines because of the low background noise of rural environments. (p.7,8.) [Pedersen and Waye 2007]
Residents living near newly constructed large wind turbines in the town of Byron, Fond du Lac County, WI, testified at the public hearing held by the Town of Union Plan Commission that they currently experience adverse health effects from wind turbine noise such as sleep depravation and disturbances, headaches, nausea and dizziness. The SPL from the wind turbines in the Town of Byron is greater than 45 dBA at their residences and can be heard inside of their houses and outside in their yards. (p.7, 10)
Two Town of Union Plan Commissioners visited turbine sites in the Town of Byron and confirmed that the wind turbines were a significant source of noise.
Doug Zweizig, acting chair of the Plan Commission, noted that the turbines sounded like a jet airplane when describing the quality and intensity of the sound.
Commissioner Dave Pestor spoke with residents, farmers and a sheriff's deputy in the area who all stated the turbines were noisy. Commissioner Pestor also took noise readings at the home of Gerry Meyer, who has a turbine about 1500 feet from his house. The sound measured from 57 to 67 dBA on June 6-7, 2008. Commissioner Pestor also took sound measurements from several wind turbines in the area. The lowest sound measurement was 48dBA and the highest was 69dBA.
Study Committee members, Jim and Cathy Bembinster, visited the Montfort, WI wind turbines in August of 2007, and measured sound levels to be between 48 and 53 dBA and 62-73 dBC [a dBC reading measures low frequency noise as well]. They also found two pieces of broken blades, with the tip of the blade being as big as the hood of a truck. The Bembinsters visited Monfort again in November of 2007 and measured sound above 60dBA and 65dBC.
When Commissioner Kim Gruebling visited turbine sites in Byron, Lincoln and Monfort, he found that overall, people were satisfied with the turbines. Two issues Commissioner Gruebling noted were tensions between landowners profiting from the wind turbines and those landowners who did not, and the poor conditions of roads following the installation of the turbines.
Commissioner Doug Lee visted wind farms in Iowa and estimates that about 60% of the people he spoke to had positive opinions about the wind turbines, and about 40% had negative opinions.
Commissioner Eric Larson went to a wind farm south of Rockford, IL. No one was available to talk, so he walked around the area. It was a nice day, and windy. Commissioner Larson notices that the windows in the homes surrounding the site were all closed and no one was outside. He stated the noise was similar to a plane going overhead. He stood under a tower and did not feel any unease. (p.7-8, 11)
In order to reduce the risk of negative health impacts from large wind turbine noise, acoustical engineers, George Kamperman and Richard James, recommend:
a) audible sound limits based on pre-existing background sound levels plus a five decibel allowance for wind turbine noise.
b) or SPL not to exceed 35dBA within 100 feet of an occupied structure, whichever is lower,
c) and a dBC limit not to exceed 20dB over ambient background levels.
NOTE FROM THE BPWI RESEARCH NERD: To read the complete Town of Union Findings Regarding Impacts of Wind Turbine Noise, [click here]
Coming up: Town of Union findings regarding Setback Distances from Wind Turbines.