How Loud Are Wind Turbines?

One of the few cons of wind power is its purported capacity to generate a constant yet subtle noise. People seem quite split on the issue. Some say the noise is minor and dissipates after a few hundred meters, while others say it carries on for miles and disturbs their quality of life. Wind companies, scientists, governments, and angry residents have all found themselves clashing over the sound of wind power, and researchers are finding ways to make the turbines even quieter. Some who live near onshore wind farms even claim the noise is causing elevated stress levels and health effects, an illness called “wind turbine syndrome.” Wind advocates say that any noise pollution stemming from wind turbines is a minor issue compared to the long-term environmental damage caused by burning fossil fuels, especially considering that daily life is full of all sorts of loud noises.

The noise of a wind turbine is a function of its distance and the surrounding environment. At a distance of 300 meters, a wind turbine puts out about 45 decibels, which is equal to the average ambient noise level in a rural area.

The Sound of Wind Power

The sound of a wind turbine is mainly created by those generators housed within the nacelles can also create a constant droning or humming noise, though this is more common in older turbines.

As with any noisy object, the closer you are, the louder it gets. If you move away from the sound, it will become quieter until it eventually blends in with the surrounding environment. The Inverse Square Law says that sound is reduced by a factor of four when the distance is doubled. This is the same for wind turbines. If you were to climb up the tower and place yourself right in front of the rotor of the turbine, the sound level will be around 100 decibels, or equal to a lawnmower. Long-term exposure to this level of noise can cause hearing loss.

Wind turbines average 60 to 80 meters in height, so if you come back down to the ground the noise level will be reduced. Standing on the ground in front of a turbine, noise levels might be around 60 to 80 decibels. This is equal to the sound level of vehicular traffic in a major city. While definitely noticeable, two people would still have the ability to carry on a normal conversation with ease.

As you begin to walk away from the turbine, the sound level begins to decrease significantly. By the time you reach a distance of several hundred meters, the noise levels will be around 35 to 45 decibels. This is the same as the ambient noise level in a rural setting. It’s important to note that wind turbines are strategically placed in windy areas, and the sound of the wind can quickly drown out the noise from a turbine at a relatively short distance.

There are times when wind turbines do get quite loud. During storms or weather events with strong winds, the faster rotation of the turbine’s blades will definitely make some noise. But in these situations, the sound of the turbine will be drowned out by the sound of the storm. Mechanical malfunctions in the turbine can also cause them to make more noise than usual.

Turbines in Residential Areas

Wind turbines are normally placed in remote areas, far away from population centers. A few wind farms may be near residential zones, but these are few and far between. Generally speaking, living near a wind turbine means living in a sparsely populated area. They tend to be in rural settings, where agrarian farm life is the norm. These areas are pretty quiet compared to large cities and suburbs, hence why the sound of a wind turbine can be considered a nuisance.

To make sure that residents don’t have to contend with the noise generated by a nearby turbine, they are never placed less than 300 meters from a home. At this distance, the sound from a wind turbine will blend into the ambient noise level.

Complaints of Turbine Noise

The past ten years have seen a rise in the proliferation of wind power, which has become the fastest-growing renewable energy source worldwide. Globally, wind is second only to hydropower, and in the US, wind energy is the most consumed renewable resource. Wind turbines are everywhere, and more are going up every day. Many welcome the use of green energy, but as with any new phenomenon, wind power has faced backlash. Along with the alleged danger to birds, noise complaints are one of the few cons of wind energy.

It didn’t take long for those living near wind farms to begin complaining about the noise. Many claim the sound of the turbines interferes with everyday life. The constant whooshing or humming sound has been said to be a major nuisance, along with the visual impact. There are plenty of scathing media reports labeling wind farms as “noisy eyesores.”

Infrasound & Alleged Health Effects

While we don’t always hear a wind turbine, that doesn’t mean they don’t make noise. Infrasound is low-frequency noise that can’t be picked up by humans without sensitive equipment. While inaudible, infrasound can be perceived by humans in the form of vibrations. Some reports even say that infrasound can have noticeable effects on human health.

There is some evidence that wind turbines do emit some infrasound. Whether or not it’s enough to cause health problems is up for debate. Still, there have been numerous reports of “wind turbine syndrome,” where people who live near wind farms experience all sorts of ill health effects. Symptoms include fatigue, headache, insomnia, heightened levels of stress, irritability, mood swings, and even nausea. Wind turbine syndrome hasn’t been extensively studied by scientists and has only been observed in a relatively small number of people. Those who work on wind turbines have been said to feel discomfort from the sound.

The truth is that while infrasound can make humans uncomfortable and can be a source of annoyance, the phenomenon is everywhere. Infrasound comes from a number of sources; cars, household appliances, and anything else that creates audible noise. Like any other sound, infrasound becomes a problem at high decibel ranges.

A Matter of Opinion

Loudness is subjective. What is loud to one person is mild to another. The nuisance caused by turbine noise is related to personal sensitivity. New technologies are often looked upon with distrust, and those who already have a negative opinion of wind turbines are more likely to be bothered or annoyed by the sound.

The symptoms of wind turbine syndrome can be tied to numerous other ailments. There’s also plenty of people who live in much noisier environments, like in large cities or near busy highways. As a matter of fact, the health effects caused by the noise levels in large cities are well known. Health effects from noise pollution include cardiovascular issues, heightened stress, tinnitus (ringing in the ears), and insomnia.

It’s also important to remember that noise levels can vary significantly between specific wind farms. The sound emanating from the turbines is heavily dependent on the turbine model, length of the blades, local wind conditions, the environment, and the proximity to homes and businesses. Some wind farms may be pretty loud compared to others.

Compared to other forms of energy, wind turbines are pretty quiet, especially when you factor in fossil fuels. Oil refineries, coal mines, and power plants tend to be much louder. They’re also more likely to be placed in populated areas. Even if wind turbines do generate some noise, it still doesn’t come close to the noise pollution from a fossil fuel plant.

Reducing the Noise Level

In essence, wind turbines aren’t as loud as the naysayers claim. But just to avoid any complaints, wind companies want to make them quieter. At the same time as researching recyclable materials for turbine blades, researchers and engineers are also busy devising ways to make sure their machines don’t make any excess noise.

Aerodynamics play a big role in how loud wind turbines are. More aerodynamic blades make less noise. The easier the blade can cut through the air, the quieter is it. This also has the side effect of increased efficiency as well. Researchers have gone in-depth into the acoustics of wind turbine blades, so much so that they can differentiate between the sounds made by the leading edge, the blade tip, and the trailing edge. This allows engineers to isolate the noisiest parts of the blade and design quieter rotors.

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The speed of rotation also affects the noise levels. The faster they spin, the louder they are. On the flip side, wind generates noise too, so on an especially windy day, the increased sound levels from the turbine are likely to be drowned out by the equally noisy wind. Still, engineers factor in noise when calculating the tip speed ratio of a turbine. This is the ratio between the wind speed and the rotational speed at the tip of the blade. Tip speed ratios that are too high will cause the blades to spin faster for a given wind speed, which results in higher noise levels.

Newer wind turbines are equipped with sound dampening systems to reduce noise emissions. These systems employ insulation inside the nacelle to reduce the sound of the machinery. The gearbox and generator may also be constructed and mounted in a way that reduces the sounds of its moving parts.

Several governments have even passed laws that require the noise from turbines to remain under a given level at a certain distance. Denmark has strict laws regarding wind turbine noise. Turbines must not be less than four times the height of its tower to the nearest home, and sound levels are capped at 38 to 44 decibels depending on the type of dwelling. The sound from the turbine is also measured in groups. If a wind farm is already at its decibel limit, new turbines cannot be built if the combined noise level will exceed the limit.

Conclusion

Wind turbines make noise; every moving object does. It’s also important to note that the blade tip speed can exceed 100 miles per hour, meaning the blades are sure to make some noise. Yet, the loudness of a turbine is still up for debate. Standing under a wind turbine will expose you to sound levels around 100 decibels, but the noise levels quickly drop as you move away from the turbine. At a distance of a few hundred meters, the noise from the turbine is no louder than the ambient noise level. Still, some who live near wind farms maintain that they experience negative health effects, with symptoms that include headaches, insomnia, and fatigue. This is called wind turbine syndrome, and its existence is hotly debated. While several other ailments can cause these symptoms, some claim that low-frequency noise from the turbine, called infrasound, is actually to blame. Wind companies have been hard at work to resolve these complaints by making quieter and more efficient turbines.