Now, let's talk about noise.
What do you think measures higher on the decibel scale … a wind turbine in motion or a bird call? You might be surprised at the answer, but the bird call registers 43 decibels while a turning wind turbine registers only 39.
Although it's a common perception that wind turbines are loud, the industry has developed solutions to reduce the associated noise levels.
Wind turbines most commonly produce some broadband noise as their revolving rotor blades encounter turbulence in the passing air and is usually described as a "swishing" or "whooshing" sound. Some wind turbines (usually the older models) can also produce tonal sounds; almost a "hum" or "whine" at a steady pitch and is sometimes caused by mechanical components in the nacelle, or housing unit. This problem has been nearly eliminated with the use of anti-vibration components in turbine design. Center bounded mounts can isolate vibration, control shock and reduce noise due to structure borne vibrations, bringing the noise level to a comfortable 39 decibels, about the same noise level as a running refrigerator.
Anti-vibration mounts drastically reduce the noise created by mechanical components so that the most audible sound is that of the wind interacting with the rotor blades. This light swishing sound is much quieter than other types of modern-day equipment and people can carry on a conversation at normal voice levels even while standing below a turbine on a windy day.
Since wind farms are located in rural or low-density residential areas the background noise, including bird calls, tends to be lower than in urban areas. This allows sound to travel further and may help support the perception that wind farms are noisy. However, wind farms are usually located where the wind speed is higher than average, and even in generally quiet rural areas, the sound of blowing wind is often louder than the turbines.
The closest that a wind turbine is typically placed to a home is 300 meters or more. At that distance, a turbine will have a sound pressure level of 39 decibels or lower.
Take a look at the chart above to see how wind turbines compare to other common sounds.
Noor Bokhari, a Marketing and Communications Intern at LORD, contributed to this blog.