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People living near large proposed wind farms are often worried they will be a source of noise disturbance, especially in high winds. But what about small wind turbines - are they noisy? The straight answer is that no working turbine is going to be completely silent. There are actually two sources of noise to think about. The obvious one is the swoosh of the blades going around. But unless you are very close, or it's very windy, this is unlikely to be much of a problem.
The main source of noise - and vibration - is caused by the magnetic generator that produces the power as the blades turn around. This isn't too noticeable at low wind speeds, but usually gets much louder at the higher, more energy-producing wind speeds. As any acoustic engineer will tell you, this noise/vibration will resonate through anything the turbine is attached to.
When we review wind turbines, we always try to add as much information as we can about the noise levels, usually giving the info in terms of Decibels, but what does this mean?
10
| The sound of breathing
| 20
| An whisper or the noise of rustling leaves
| 30
| Background noise of a rural area
| 40
| The humming of a fridge or the sound of a quiet wind turbine like the Evoco Airsurfer | 50
| The general level of conversation or a slightly larger turbine like the QR5 | 60
| The noise level in an office or at 79 feet from the relatively large ReDriven 20kW
| 70
| A vacuum cleaner or a motorway from 15 meters
| 80
| A freight train from 15 meters distance
| 90
| Food blenders, busy city streets and diesel lorries | 100
| The noise of a jet plane taking off 300 meters away
| 110
| A car horn a meter away from the ear
| 120
| Thunder or live rock music - The human pain threshold
| | 130 | The sound of a jet taking off 100m away
| | 140 | Gun fire
| 150
| A jet taking off 25m away
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If the turbine is pole-mounted, as we recommend, then you shouldn't have too much trouble. The steel pole will channel the vibrations straight into the ground, where the earth will dampen it - you may not even notice it happening.
However, if the turbine is strapped to the side of your house, there is a good chance that some of the low vibration frequencies will be transmitted through the wall. It could even keep you awake at night.
Some improvements can be made by isolating the turbine from the structure, with specially-designed (or improvised) rubber mountings. You might cut out 2/3rds of the noise/vibration this way, but you're never going to completely get rid of the problem.
Our first turbine installation, a FuturEnergy turbine mounted on a steel-hulled boat, is an extreme case. The turbine pole is bolted directly onto the steel mast, which in turn is firmly welded to the solid steel hull of the boat. Not surprisingly, at high wind speeds, the noise is rather effectively channeled down the mast, amplified somewhat along the way, and transmitted into the living quarters of the boat. Although the boat residents initially found this noise a novelty, when the winter came, with the higher wind speeds, they understandably got a bit fed up.
It'll never be silent on a windy day, but to ease the problem, we fitted insulating rubber around the mounting, and a stop switch to give the boaties the option of safely stopping the turbine at night if it disturbs their sleep.
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