“There is a pressure pulsation emitted into the community once every second” (Wind Turbine Noise Expert)
Jul 8, 2014
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Editor’s note: Rick James is, without doubt, one of North America’s premier experts on wind turbine noise. Unlike the great majority of noise engineers who have sold their souls and ethics to the wind energy industry, Mr. James can’t be “bought.” Together with Rob Rand and Steve Ambrose, Rick has exposed the deceit and mendacity of wind company acoustic consultants — as in their fraudulent use of A-weighted noise measurements, for instance.
We all owe these three gentlemen a huge debt of gratitude.
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— Richard James, Noise Engineer (7/8/14). Click for PDF, with all graphs included.
As the blade passes the tower, the low frequency noise and infrasound is generated at a frequency related to the hub’s rotation and number of blades. These pressure pulsations appear as tones during analysis, but are not heard as tones by most people. Instead, they may feel the pressure changes as pulsations, internal organ vibrations, or as a pain (like ear aches or migraines).
This frequency is called the Blade Pass Frequency, often abbreviated as BPF.
For modern utility-scale wind turbines, this frequency is at 1Hz or lower. A three-bladed wind turbine with a hub rotation of 20 revolutions per minute (rpm) has a BPF of 1Hz. This means there is a pressure pulsation emitted into the community once every second. At 15 rpm the BPF is 0.75 Hz; and at 10 rpm, 0.5 Hz.
When wind turbine blades rotate past the tower, a short pressure pulse occurs, producing a burst of infrasound. When analyzed, the result is a well-defined array of tonal harmonics below 10 Hz.
For impulsive sound of this type, the harmonics are all “phase-correlated.” This means the peaks of each occur at the same time. Thus, the peaks add together in a linear fashion, with their individual maximum sound pressures all coinciding.
Thus, for an impulse having 4 equal amplitude harmonics (BPF, 2nd, 3rd and 4th) each of the same amplitude, the peak level is +12 dB. Ten equal harmonics would produce a peak level of +20 dB.
Comment by Kaz Pease on 07/09/2014 at 7:18 pm
I am sitting here in my peaceful home in rural Maine, watching the sunshine creep down the mountains as it rises behind me, and listening to the robins and the chickadees begin their day with uplifting songs. I am surrounded by beauty and yet — I am troubled.
From where I sit, nothing has changed. Maine is still under siege by industrial wind developers. But Maine is a tiny part of this massive wind energy effort. Friends in states all around the country and in Canada, Europe and Australia are being driven from their homes — and they are the lucky ones. Others cannot leave and are forced to endure physical, emotional and mental anguish. Financial ruin. Ridicule and insult.
Where are we? Are we burned out? Too tired and disheartened to continue to fight? Have we given up? Admitted to ourselves that we cannot succeed?
I know that, individually, we’re still in this fight — doing what we can, where we can. We still write letters, still show online support for friends who are suffering and still answer calls when we can.
But our true power is in coming together, isn’t it? Everywhere we look, there are heroes. Doctors, acousticians, the rare politician and reporter — each standing up and speaking out. Brave — but often alone. And then what? Then they are rebuffed, maligned, ignored. . . .
I know we are tired. Discouraged. I know I am.
But I also know we can’t give up. When we back down, when we rest, when we let our guard drop, the industry moves in to take advantage. It knows what it’s doing. It has a well-orchestrated plan.
Do we?
Sending my love and thanks to all who have given (and are giving) so much. Some might say “too much.” But it’s not enough yet, is it?
Hugs from Lexington Township, Maine
Kaz
Comment by Marshall Rosenthal on 07/09/2014 at 9:23 pm
Cheer up, Kaz. Celebrate with me the the stopping of the mega-watt monsters from Peru and Cheshire, MA. I think serious persons listened to us and found ways, separately, to ban the IWTs from their communities.
In Peru, it was done by getting a 2/3 + 1 majority! (Who says there aren’t any more miracles?) Backyard renewable energy production is permitted, provided 50% is sold to the grid — which I doubt anyone will do.
The news, now, that turbine neighbors are getting zapped every second with volleys of infra-sound (which is horrendous, assaultive, and monstrously offensive), seems to have escaped the attention of most of the legal community, not to mention the Supreme Court of the United States. Since when was it ok to inflict mayhem on the citizens of this nation?
I think this bullshit can only be stopped by the highest court of the land.
Comment by Valerie Malicki, MA, LPCC on 07/10/2014 at 9:27 am
Yes, under siege everywhere. We have a 25-turbine proposed project with over 900 homes within a mile. (Most are much closer, really. Ohio only requires, under old law, a setback of 1150 feet.) Our lovely public school is about 1.8 miles away. Lovely park, a mile away. About 80% of the entire village is within a mile and a half of turbine #14.
Hearing the birds chirp this morning. I see many lovely red cardinals (Ohio’s state bird) and brilliant blue bluejays. A bald eagle family lives nearby,and one farmer has seen golden eagles. For now.
I’m a born and bred Ohio country girl. It saddens me that we are being bullied and threatened to leave our home, this little chunk of paradise for us, that we have worked hard to have and keep. It’s our home, our community, our family our friends. It saddens me.
Thank you to Rick James. Thank for not being “bought.” Thank you to Dr Pierpont, Esther Wrightman, Dr Calvin, Dr Sarah Laurie, Patina, Mike McMann, and so many willing to SPEAK the truth.
If we don’t speak out, who will?
Yes, Marshall, I saw the reported Peru victory. I still believe in miracles 🙂 I saw it was by one vote. Amazing! Who says one vote, one voice doesnt count? 🙂