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Wind turbines are such great renewable energy generators. Modern manufacturers have made small wind turbines that can produce between 400W to 600W. People who live off the grid or in the suburbs are switching to this energy source for cheaper electricity bills.
However, wind energy has its drawbacks. The energy production depends on the weather, so it won’t be enough on some days. The turbines also emit annoying background noise that may affect nearby people. This article will explain wind turbine noise and the guidelines about residing near it.
How Loud Are Wind Turbines?
A wind turbine’s noise level depends on its distance from your home. The minimum distance from your house should be 300 meters; the turbine reaches 43 decibels at this distance.
This noise level is louder than a fridge which only runs at 40 decibels. However, the average air conditioner runs at 50 decibels, so it isn’t unbearably loud.
If your home is 500 meters away, background noise will drown out the wind turbine’s noise level. The surrounding sound reaches 45 decibels while the turbines drop to 38.
The “swooshing” sound comes from the blades moving through the air. The turbine machinery also makes a noise that gets louder with solid winds.
Underwater noise
Offshore wind energy, which comes from the sea air, is popular due to its strong force. Some people have started raising concerns about noise pollution’s effect on nearby marine wildlife.
The noise generated by these turbines is 10 to 20 decibels lower than a ship’s. Still, putting several together on a wind farm may have a more severe impact.
Researchers found that the noise generated from wind farm construction is worse than during its operation, so keeping a distance from the water will prevent low-frequency sound pollution.
Amplitude Modulation
Amplitude modulation is the term scientists use for wind turbines’ “swoosh” sound. Some studies show that this sound has a higher frequency at night, almost five times louder than during the day.
This sound production may negatively affect people’s sleeping patterns, especially those who live downwind from the turbines.
Fortunately, scientists are using machine learning to detect and monitor the wind turbine’s estimated evening amplitude modulation. This data will help people to choose where they live.
Types Of Wind Turbine Noise
Modern wind turbines are quieter than their counterparts from the 1980s. However, you can hear the gear sounds when you approach the structure.
Wind turbines produce four different sounds:
- Tonal Noise
- Broadband Noise
- Low-Frequency Noise
- Impulsive Noise
Tonal Noise
These noise frequencies come from the turbine’s meshing gears. These sounds also happen when the blade’s blunt edge moves through the air.
Broadband Noise
Broadband noise is the signature “whooshing” noise you hear from wind turbines. Atmospheric turbulence causes this noise, and the sound reaches 100Hz.
Low-Frequency Noise
This sound comes from downwind turbines, and it’s between 20 to 100 Hz. People typically don’t notice it, so it causes flow deficiencies.
Impulsive Noise
The downwind turbine makes sudden thumping sounds when the airflow around it is disturbed.
What Creates Wind Turbine Noise
Various components in the wind turbine create noise. These are the most common sound sources:
Mechanical noise
These sounds come from the working structural parts of the wind turbine, such as:
- The generator
- Hydraulic systems
- Gearbox
- Yaw drives
- Ducts
- Cooling fans
Parts like the nacelle and rotor amplify these sounds as they travel through the structure. You can control this noise damping and vibration suppression.
Aerodynamic noise
Aerodynamic noise is the most common cause and is also the most difficult to manage. The “whooshing” sound comes from turbulence when it hits these parts of the blade:
- The laminar boundary layer vortex shedding
- Turbulent boundary layer trailing edge
- Separation stall
- Trailing edge bluntness vortex shedding
- Tip vortex formation
- Turbulent inflow
You can reduce this sound by lowering the blade’s rotational speed and increasing the pitch angle. However, doing these will decrease the wind farm’s power output.
Wind Turbine Noise Health Effects
Wind turbines generate low-frequency sound; you may not hear it, but the sound waves can affect your eardrums and heartbeat. Prolonged exposure to the sound waves can cause health issues like:
- Headaches
- Fatigue and dizziness
- Difficulty concentrating
- Irritability
- Sleep disturbances
Some people even develop epilepsy and coronary heart disease after prolonged exposure to these sounds. Several countries like the United States, the United Kingdom, Finland, and China have developed noise regulation policies to prevent adverse health effects from low-frequency sound waves.
How Can Manufacturers Lessen Turbine Noise?
Manufacturers of modern wind turbines aim to make quieter machines, so they’ve developed ways to produce less noise pollution.
Less moving parts
Older wind turbines had more parts than their modern counterparts, making more mechanical noise. Now, fewer parts mean a lesser chance of creaks and squeaking.
Upwind rotors
People who construct turbines for wind farms let the rotors face upwind. Upwind rotors increase the wind energy yield and reduce the “thumping” from aerodynamic noise.
Soundproofing and dampening
Manufacturers dampen the rotor to lessen vibration and add soundproof features to the nacelle. These features create less aerodynamic noise.
Get inspiration from nature
Engineers are using biomimetics to study the characteristics of birds’ wing movements, which are undetectable when they fly. They use their wing design to develop more efficient, soundless blades.
How To Manage Wind Turbine Noise Pollution
Manufacturers have developed unique features for modern wind turbines to reduce noise production. Several countries, like Denmark, have also developed regulations regarding noise to complement these features.
These statutory orders help to guide developers on the distance they must leave between the farm and residential areas. They also develop guidelines for the measurement of wind turbine noise levels.
Wind farm owners must be responsible for installing and maintaining the turbines they construct. Here are the guidelines and noise limits these owners must follow:
For residential areas in the open countryside
- The farm must be 500 meters from the closest dwelling.
- Wind turbine noise mustn’t exceed 44 decibels with 8 m/s wind speed and 42 decibels for 6 m/s wind speed.
For noise-sensitive land
- Noise mustn’t exceed 39 decibels for 8 m/s wind speed and 37 decibels for 6 m/s wind speed.
- The combined low-frequency noise from windmills mustn’t exceed 20 decibels.
Suppose owners want to modify their wind turbines. In that case, they must notify their municipal council, especially if the modification will increase noise production. These guidelines will prevent unnecessary disturbance with residents living nearby.
Conclusion
Wind turbines are a popular alternative energy source. Sadly, these structures produce annoying background noise, negatively affecting nearby residents and wildlife.
Local governments must develop strict guidelines to regulate the noise pollution from these structures. Wind farm owners must also be responsible when constructing their turbines and requesting appropriate permits from their municipal council.
Modern innovation and technology like machine learning can help predict the estimated noise production. This data can help developers plan their layout for residential areas to avoid being downwind from the windmills.
New construction methods for turbines make them more soundproof than the older models. Following guidelines and learning from data will help wind farm owners and residents coexist peacefully. There will be fewer adverse effects from noise pollution, and wind farm output productivity will continue to increase.