Wind turbines are surprisingly quiet, considering their size. Most of them placed at a distance would blend into the natural noise of trees, wind, and birds chirping, and they would be hardly recognizable to your ears.
A wind turbine at a specified distance of around 400 yards would make less noise than your air conditioner or dishwasher. However, standing underneath one is incredibly quiet as the noise is broadcast outward, and this is also why there are minimum proximities required for residential placement.
Let’s look at the factors that create noise in wind turbines:
- What causes the noise from wind turbines
- Is wind turbine noise dangerous
- Are modern wind turbines less noisy
- Examples of modern low-noise turbines
We can now explore what noise levels they produce and whether there are any potential harmful effects from the different frequencies of noise they make.
How Do Wind Turbines Make Noise
Most of the noise you hear from a wind turbine is caused by the sound of air moving over the blades. This includes noise from the wind moving over the blade tips, trailing edge, turbulence from in-flow, and the interaction between the blade and the tower.
Wind noise will increase as wind speed increases and lower with less wind velocity, and as the rotor speed increases, so does the noise level, which can make wind turbines quite loud, especially at night when the daytime ambient noise is gone.
What Kind Of Noise Do Wind Turbines Make?
Wind turbines emit both high and low-frequency noise while operating, and the low-frequency noise can be the most harmful to people if it’s loud enough. Strict regulations have been put in place regarding the placement of wind turbines from residential areas.
Low-Frequency Noise or LFN is emitted between frequencies of 20hz-200hz, so in terms of sound, this is a low to mid-bass spectrum and would sound like a low hum. At around 400 yards, the sound would be as loud as your air conditioner or dishwasher.
The further away you go, the less noise, and getting to about 800 yards or more, the sound would be barely perceptible, and out further from that, you’d hardly know it was there.
Bear in mind that ambient low-frequency noise like traffic and other sounds from the urban environment would also interfere and make the wind turbine noise indistinguishable from the background.
How Can LFN Affect Human Health
Studies done and published in The Journal Of Acoustical Society Of America show that exposure to LFN can affect human health adversely. The effects range from mild to severe.
The milder symptoms would include sleep interruption and associated disturbances, irritability and annoyance, and increasingly more serious conditions like tinnitus, headaches, and exhaustion.
Further up the severity scale, you would have the potential for hearing loss, anxiety, chronic fatigue, and impaired concentration.
What Other Dangers Do Wind Turbines Pose
Aside from the risks to people, wind turbines and the noise they also affect wildlife and birds are common casualties of the heavy spinning blades.
Fortunately, developments in technology and design (which we’ll look at further) will reduce the impact on wildlife.
Are Modern Wind Turbines Less Noisy?
Comparing a wind turbine from the 1970s and 1980s to the ones made today is significantly less noisy than the earlier models. This is because the gears and the generator produced considerable noise relative to their power output.
Improved blade design, noise dampening technology, and better structural design of the gears and generators mean that a modern wind turbine pushing out 2-3MW of power is about as loud as a tractor.
Compared to the older ones, which only produced around 500kW in the 1990’s and only 100kW in the 1980s with higher noise levels, they were far less efficient and emitted more noise than the modern bladed turbines do now.
Modern Wind Turbines Are Super-Quiet
Over the past decade, engineers have been looking at how to make wind turbines less noisy and have come up with some innovative designs.
Aside from the noise dampening system used on gears and generators – which constitute a small percentage of the generated noise – they have improved blade design and configuration to make wind turbines more efficient and much less noisy.
The Liam F1 Urban Wind Turbine
Designed and produced by a Dutch company, The Archimedes, the Liam F1 is a compact, totally silent, carbon-neutral wind turbine installed in urban areas. Its shell allows the turbine to position itself for the best wind position and is designed like the Nautilus shell.
At a wind speed of just 5 meters/sec or 16.5 fps (11.25 mph), this super-efficient and super quiet turbine can generate a staggering 1.5kW hours of energy which is about half the average power consumption in a Dutch home.
If you then consider placing these in windy locations in the USA, generating that kind of power with no noise and combined with solar could provide a very sustainable energy source for centuries!
Vortex Bladeless Turbine
The Liam still has blades even though they are more shell-shaped than blade-like; the Vortex is bladeless, which removes a huge chunk of noise from the turbine. They are designed in a funnel shape and can produce around 100W of power per unit.
Another innovation is from the French company New Wind that produced their ‘Wind Tree’ turbine or L’Arbre A Vent, and it uses a series of ‘Aeroleafs’ to generate power from gentle light winds.
The Aeroleaf system is a series of 72 micro-turbines mounted on a vertical axis. These are super-efficient at catching the slightest breezes and are another excellent option for installation in urban areas.
With the growing demand for clean energy, a few other noiseless wind turbines have been developed for the urban market, and those are available now.
Some of those are the magnetically driven Honeywell Turbine, The Skystream, and The Stormblade, as well as The Quiet Revolution Turbine and The Swift Wind Turbine, all of which are noiseless and efficient.
Whether industrial or urban, modern wind turbines have come a long way in generating capacity and noise reduction efficiency. As soon as the technology evolves, both versions will be noiseless.
As that evolution occurs, the appeal of quiet but efficient energy generation will become a viable solution to the world’s urban and industrial energy problems; we just have to hope that the oil giants will see it the same way!
Resources:
- https://asa.scitation.org/doi/10.1121/1.414863
- https://www.wind-watch.org/video-fonddulacnoise.php
- https://link.springer.com/article/10.1007/s40201-020-00478-9
- https://eng.mst.dk/air-noise-waste/noise/wind-turbines/low-frequency-noise-from-wind-turbines/
- https://www.herox.com/blog/501-noiseless-wind-turbines-unveiled
- https://www.networx.com/article/the-quietest-wind-turbines-on-the-market
