Nobody denies the reality of wind turbine noise. These massive machines make a specific sound when they work, but is this actually something to worry about? Something that can affect your health? While most people are generally unaffected by such matters, there are those who claim possible health issues.
Consequently, the noise generated by a wind turbine has been a contentious point over the past decade. Many have argued that it is harmless and, at certain distances, barely audible. To answer this debate, we’ve put together a series of objective facts that can help us achieve a resolution.
What Does a Wind Turbine Sound Like?
Although recent wind turbine types are significantly more silent than the models issued in the 1970s and 1980s, they still issue a specific sound when they are active. Most people who experience this sound describe it as a hiss or a swish through the air, which results mainly from the turning blades of the turbine.
Manufacturers are working to improve the design of the blades in order to lower the noise even further, but for now, it is impossible for turbines to function without making this sound. In addition, the generator and gears built into the turbine can also emit a type of machine noise that some listeners find very annoying.
Sure enough, this sounds like it should be a concern. But how far can you actually hear this type of wind turbine noise and will it really impact your life if you live nearby? And is the amount of wind energy created a worthy trade-off?
How Much Wind Turbine Noise Are We Talking About?
Here’s the thing. If you’re sitting right on top of one of the blades of the wind turbine, you’re likely to experience about 105dB of noise, which is comparable to a lawnmower. As you distance yourself from the machine, at about 10 or 20 meters, the noise is rated at 90dB and 80dB, respectively – basically, a blender or a vacuum cleaner. This can be pretty loud, especially if you have to hear it consistently throughout the day.
However, no home should ever be that close to a wind turbine in the first place. At 100 meters, wind turbine noise is already at only 50 dB – as loud as the sound of a regular window AC. But the shortest recommended distance between a wind turbine and a home is 300 meters and, in most places around the world, you’ll rarely find a home closer than 500 meters from the machine.
At this point, the noise ranges between 40dB and 30dB, whereas background noise is usually rated at 40-45dB. In essence, you won’t even be able to tell that a wind turbine is operating nearby because the sound will be lost in the background. Even if you could hear it, it would only be as loud as the fridge in your kitchen.
The Inverse Square Law and the Principle of Attenuation
In spite of countless studies and evidence to the contrary, critics of wind power continue to uphold that wind turbine noise can be detrimental to human health. Physics, however, basically demonstrates that such hypotheses are groundless.
For one, the inverse square law states that when you double the distance between yourself and a source of noise, the loudness of this noise decreases to only a quarter of what you would hear at your initial position. At three times the distance, you only hear a ninth of the initial noise, and so on. This is not to say that, when you’re very close to the wind turbine, you won’t hear it work. But some critics claim that the noise can be heard over a distance of 5km, which, according to this law, is nothing short of absurd.
In addition, the principle of attenuation is also at work here. As sound waves travel, the air absorbs part of their strength, especially when the noise must pass through dust and mist. The sound is therefore diminished as it travels further from the source, which makes it highly unlikely that homes more than 1km away from the turbine can hear it work.
How People Perceive the Noise
It has been difficult to settle the ongoing debate about wind turbine noise partly because the way this sound is perceived can differ according to a number of factors. These include the distance between turbines and homes, wind pattern and strength, weather conditions, background noise, and even individual sensitivity.
For example, the wind blowing in a certain direction can increase the strength of the sound in the same direction or, in other words, might carry the noise from a wind turbine closer to homes in its path. Rain or mist, on the other hand, can mitigate the noise. Furthermore, whether or not a turbine is audible also depends on the level of noise of the surrounding area. In an empty field, you are more likely to hear the swish of the blades than you are in a busy residential area.
Finally, whether you find a particular sound annoying can depend on several factors, from your personal sensitivity regarding noise, to the type of wind turbine axis, to your location and even your mood on a given day. All of this is very difficult to factor into scientific research that would either prove or disprove the harmful effects of wind turbine noise.
Is Wind Turbine Noise Actually Something to Worry About?
The short answer – no (unless, of course, you live right under a turbine). Even the largest wind turbines in the world do not make enough noise to bother people who live more than 1km away. Scientifically and physically speaking, there is no reason to worry that a wind turbine would be too loud, but if you want to make sure, you can always arrange to visit one nearby.
During your stay, you can walk up to the base of the machine and at various distances from it to see what the sound is like and whether you find it annoying. You can even spend a few days in the area so that you get a better idea of how wind turbine noise changes in different weather conditions, as well as over longer periods of time. (Want a closer look at the pros and cons of wind energy? Click that link!)