Measuring Wind Turbine Noise

There have been a number of stories recently about how turbine noise impacts people who live close to wind farms. Inevitably, the conversation comes back to whether the turbines are too loud.

Measuring decibel levels is extremely important, as it is an objective way to compare the sound to everything else around us.

You may have seen this nifty diagram released by GE last week:

As you can see, a large wind turbine isn’t very loud from an objective standpoint. According to this data, at a very close distance of 300 meters away, a turbine will be somewhere between an air conditioner (50 decibels) and a refrigerator (40 decibels). At about 500 meters, the levels drop to about 38 decibels, which is well below the typical 40-45 decibels of background noise in a populated area.

So if wind turbines aren’t any louder than what we’re already used to, why are some people complaining about them?

It comes back to subjective factors that decibel measurements don’t account for.

The quality of wind farm noise is one factor. Researchers are looking at whether the low-frequency woosh, woosh, woosh of blades has a different psycho-social impact than noise from highways or airports. It’s very common that people living close to turbines call the sound “penetrating.”

Of course, different people handle the sound in different ways. Many residents are unfazed by turbines at close distances. Others find them unbearable. For a developer, reaction to a project depends on what kind of people you have living in close proximity to the machines.

The other major factor is communication. If a developer doesn’t accurately describe how sound levels or sound quality may change, the potential for backlash becomes far greater. For example, a handful of residents living near three GE 1.5 MW turbines on the Maine island of Vinalhaven say that the developer, Fox Islands Wind, mislead residents about sound levels. A lot of the outrage (which has gained national media attention) was over poor communication about how the turbines would impact the soundscape of the rural island.

Clearly, these highly-variable factors are just as important as objectively measuring decibel levels.

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