Hello everyone, this is my first day here, and I'm able to post
already, yay!
In my experience, an omni below a turbine gives a sense of the sound,
but not the whole thing. I think, mush like the seashore, you need to
record different fields and mix them. Maybe a shotgun pointing right
at the nacelle =96 the bit with the generator in it. That gives its own =
sound, separate from the blades. It's a while since I've been on a
wind farm so I can't remember exactly how it sounds. Probably not the
key sound, and certainly quieter than the blades. It may help
identify the overall sound though.
Then an omni behind the turbines. And then maybe somewhere else=85
Watch out for deciduous trees, where the wind may sound similar to
the blades. Confusing!
I think Ray's suggestion of analysing it with a spectogram is key.
You'll get so much clearer an idea of what you need to pick out, and
what sort of filters you might need etc.
There's one more idea: Wind farm developments need to predict their
noise impact before getting the go-ahead. So if you can find a local
sound metering professional, they may well have measured the levels
of turbines, and have analysed the frequencies.
Good luck!
Connor
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Connor Walsh
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On 25 May 2007, at 19:04, Tim Nielsen wrote:
> Hi Mark, I've tried to record those as well. I was outside San
> Francisco, about an hour east, recording some tigers, and on the
> property were several of those huge turbine windmills. It was quite
> windy then, and I know what you mean. You can 'hear' them much better
> than the recorder can pick them up.
>
> I think it's a couple of things. First, your ear is so amazing at
> deciphering 'content' from 'noise', it's the best noise reduction
> filter there is. The mics have no such luxury. Second, it could be
> right that what you're 'hearing' is partly what you're 'feeling', a
> low pressure wave generated by the blade.
>
> I'll have to dig out my attempt at recording them and see what it
> sounds like.
>
> But it's a very neat sound to be in the presence of. We were standing
> directly underneath it, and they are massive.
>
> I'll try to post my recording if I can find it.
>
> On May 25, 2007, at 10:47 AM, Mark Fischer wrote:
>
> >
> > Hi everyone,
> >
> > So, here is an interesting dilemma, I thought I would
> > pose and see who else has encountered it, and what
> > could be done about it.
> >
> > We have some very large windmills just to my north,
> > some of the largest in the world, actually. With a 90
> > /meter/ span. (I am on the south bank of the
> > Sacramento River, they are on the north, about a mile
> > away).
> >
> > And, under unusual conditions, with winds aloft but
> > calm at the surface, you can actually hear them
> > rotating. Kind of a low-frequency 'whoosh....
> > whoosh.... whoosh....'.
> >
> > So, I thought. Very cool, I *have* to get a recording
> > of this.
> >
> > What is the result? Pretty much every sound in the
> > environment -except- these blades.
> >
> > I know I can hear them-- so why can't the microphone,
> > which can hear everything else?
> >
> > Has anyone else encountered such a thing? What kinds
> > of things can you do to pick these things up? They are
> > sounds, but they are getting pretty close to 'pressure
> > waves', or subtle changes in background. Thing is, I
> > can hear them clear as day... so what to do?
> >
> > Any thoughts or comments would be appreciated.
> >
> > Thanks,
> >
> > Mark
> > ~~~~
> >
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