Something I read from nsaspook post:
"A basic concept from the science of public health requires that a human health risk be a true hazard and that there is exposure to that hazard. This review concludes that there is little scientific evidence that sound from wind turbines represents such a risk to human health."

I guess it could be argued from several different points of view and none of the several will likely agree. Kind of like those "Ghost Hunters" with their electronic equipment. Is it really there? Or is it some other phenomena? Back in the dark ages if someone tripped they might point at an individual and proclaim that person cast a spell on them. That person may be subsequently burned at the stake for being a witch.

Like Chaos-Theory, we don't really know what we think we know and don't really "not" know what we think we don't know.

Being paid for not complaining doesn't necessarily mean there's literally something worth complaining about, but rather an attempt to quell the hype about cancer causing windmills. And we will never know what's truly behind their motives. Tobacco companies downplayed the negative affects of their products all the while working on ways to make them addictive. OK, there we know their motive. I suppose the power company in Oregon is motivated to build their wind farm and prevent people from making complaints that could derail their project. Maybe the sound IS harmful. Maybe not. Whatever the case - we little folks will never know.

Annoyance/unpleasantness seems to be the main connecting factor with wind farms and most Infrasound cases. What that 'sound' does to each individual as a human mental health risk seems to depend on a variety of conditions but I've seem nothing yet of long term physical damage to low level exposure.

 

You can't beat Google for a straw poll. If you search for "cooling fan 2800rpm" you get quite a lot of hits, so my guess is that you have at least one fan with an electronically commutated synchronous (aka "brushless DC") motor that is spinning at 2800 rpm.

My fans are variable speed but I so think that peak was fan related. Sorry if I seemed to say otherwise, The 47Hz signal is the real mystery. It's louder than any other ambient sound but apparently outside the range of my 1960's model ears—at least at that amplitude.

 

You'd think with ears like mine I could hear a very wide range of sounds. But these days my probably most common word is "what?"

 

Did not expect this much response on this thread. Thanks all. Interesting for sure.

 

Here is a very interesting paper on wind farm infrasound and the possibilities for mitigation. It has cites to sources for potential heath effects, and a discussion of the possibility of using active cancelation methods to reduce it.

I certainly learned some things from it and I am not as sanguine about wind farms located near habitation as I might have been previously, nor am I a willing to accept reports that involve A-weighted SPL measurements, or "I don't hear anything" as proof of harmlessness.

Out of interest, I used an FFT app with the weighting set to flat in my studio-lab and got this unaccountable result:

View attachment 272481
Note the peak are 47Hz, where is that coming from?
​

This is not a calibrated microphone, and not a scientific instrument but checked against my function generator with a (very) small transducer it seems reasonably accurate in the frequency domain.

The speaker connected to the generator was only about 1" in diameter. With the frequency set to 47KHz I could perceive nothing at all coming from it. Nevertheless when it was on, the 47Hz peak fluctuated with a regular pattern, and off it stopped. I surmise this was beating of the original cause of the 47Hz and the signal from the transducer.

Any ideas of the source? The next peak up in frequency is at 120Hz, so even if I don't have an exact source for that one, 60Hz power provides a reasonable cause in some way. But 47Hz ±1Hz is not something I can account for.

I would suspect the iphone audio section of having an internal resonant peak. And withthe current status of my hearing ability I doubt the sound would bother me, or that I would even notice it.

 

With the current status of my hearing ability I doubt the sound would bother me, or that I would even notice it.

Isn't this whole thing about infrasonic's? In theory Nobody can hear subsonic sounds. It's the vibrations that are in question.

 

Sound pressure is exerted over the entire body, not just the eardrums. Since it is infrasonic (and can't be heard by humans) noise-canceling earphones are useless whether they cancel infrasonic frequencies or not. The bigger question is what does the sound pressure of infrasonic waves do to the human body, if anything? Still waiting for someone to bring up the "Brown Note"!

 

There are many sources of pressure waves that are easily felt, especially in the chest. any place near a military jet getting ready to launch, or sometimes doing a fast low-level fly-by to dump BBQ. And certainly big fireworks at 59 yards distance.

 

Sound pressure is exerted over the entire body, not just the eardrums. Since it is infrasonic (and can't be heard by humans) noise-canceling earphones are useless whether they cancel infrasonic frequencies or not.

Excellent point. Thanks.

Still waiting for someone to bring up the "Brown Note"!

On that other thread this was said:

The original post is directed at EM fields and brains. I don't know if subsonic sound can cause issues but I do recall an episode on Myth Busters where they tried to find the "Brown Note", the one that is supposed to be able to make a person take a dump in their pants. MB failed to find such a note. But I have heard of infrasonic weapons being used by federal agents with their nausea causing sound beams pointed at barricaded suspects.

 

Mythbusters "brown note" experiment was flawed. They performed it in open air, with subwoofers that had negligible response down at low frequencies. They should have used a small sealed room (or vehicle) and sealed-box subwoofers.

 

Mythbusters "brown note" experiment was flawed.

I used to watch them all the time. Often times I'd see issues with the way they approached a myth. Yes, their experiments are often flawed. They portray themselves as really smart, but an education doesn't necessarily mean intelligence. Intelligence and smart are not the same thing. I've seen intelligent people do some really smart stuff and I've seen some smart people do some really dumb stuff.

 

At one time my department did an experiment with a bucket seat and a 200 ponds force shaker, which if you can imagine a magnetic speaker able to deliver 200 pounds of force out through a ten inch voice coil. This was coupled to a light weight Hi Bscked bucket seat supported on four spring steel flexures.ndall mounted on a pair of 2by6 inch steel channels, flatwise. The initial plan was to investigate seat resonance, but very soon people sat in it. The movement was not much at 400 hz, but as the frequency was lowered the moves got bigger. down below one Hz the motion was quite a bit. And no accidents were reported, although some frequencies were not comfortable.
While most folks can not afford s shaker system like that a variable speed motor with an eccentric on the shaft can provide the lower frequency portion quite well. The possible applications can be a lot of fun. I leave the details to adult imagination.

 

If I recall correctly, what I believe I've seen was a sort of gas cannon. Not that it shot anything, no, but rather it was used to generate powerful shockwaves through the air directed at a target. It didn't destroy or damage the structure but it was supposedly intended to nauseate the people inside causing them to decide to surrender. I wish I could find that video on YT.

 

While searching YT for something like that mentioned I came across this. This is going in the "COOL" thread too.

 

If I recall correctly, what I believe I've seen was a sort of gas cannon. Not that it shot anything, no, but rather it was used to generate powerful shockwaves through the air directed at a target. It didn't destroy or damage the structure but it was supposedly intended to nauseate the people inside causing them to decide to surrender. I wish I could find that video on YT.

The toy version was the "Sonic Blaster", CA 1962. my brother still owns one, .Quite a fun toy!

 

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