Hi

This is not an easy subject and I am not an expert in any way on infrasound so please take what I write with a grain of salt.

For what it is worth. 

Wind mills is one such item where infrasound is debated. Here is one side

http://acousticstoday.org/issues/2013AT/Jul2013/#?page=30

and here is a reply

http://acousticstoday.org/issues/2013AT/Oct2013/#?page=8 

and a some more

http://acousticstoday.org/how-does-wind-turbine-noise-affect-people-alec-n-salt-and-jeffrey-t-lichtenhan/

http://acousticstoday.org/worldwide-low-frequency-ambient-noise-david-l-bradley-and-stephen-m-nichols/

When evaluating perception of sound, and perhaps also infrasound, it is important to remember that what is wanted for person X may not be wanted for person Y and their experience hence, may oppose when exposed to one and the same phenomenon. Also, persons X and Y may have different thresholds and hence, experience matters differently. 

I am just guessing, but the guy earing money from a wind mill emitting infrasound is more likely to enjoy experienceing the machine operating than one situated nearby, in particular should it happen to cast a shadow across his property or affect his view. Similarly, base personel probably experience helicopter sound differently from those living enroute to the helicopter base. 

I talked to a very senior researcher who hade been dealing with infrasound for many years, I needed his best guess on infrasound in urban environments as it might affect a machine inside a Nanolab I was working on.

In passing, he told me that it is a sense which most people simply are not trained to use. Train a little and you can sense (and make sense of a lot of things). 

To provide an anecdotal example. I was working offshore at a platform. When located in a very noisy switchboard room with lots of noisy fans - the guy I was working with all of a suddent looked up at me and said - OK, the helicopter will be here in 25 minutes. I tried and was not able to sense a thing but, I know that helicopter sound tends to transmit well via HVAC systems and, of course, the guy was absolutely right - the helicopter did arrive 25 minutes later. 

From what I have been able to gather, Untrained people usually do not notice infrasound below a threshold level that is not that far below the human ear's pain limit (125 dB re 2E-5 Pa). Trained people probably can sense infrasound way below this threshold level. 

I once listened to a guy holding a presentation about therapeutic use of infrasound and higher frequency sound. He was quite open on it all being correlative, i.e. lacking fundamental knowledge as to why it had the effect he observed. He claimed it helped some of his patients release muscle cramps. It is easy to torpedo things like these as lacking in scientific foundation.

Then again, it is a big world out there and we are only scratching the surface.  I for one try to respect that we are still on a learning curve. 

In any case, building an understanding from human observations, it always is good to have a method to rely on. You might want to look at these

http://66.147.244.131/~claytor2/wp-content/uploads/2012/07/Theory_of_Theory_Building.pdf

and this insightful list written by S.J.Rienstra

http://qringtech.com/TryMe/wp-content/uploads/2014/01/What_is_a_model.pdf 

Sincerely

Claes

Thank you so much Claes for your views on the subject and links.

May I ask who was that guy ?

Hi 

I guess you are referring to the therapeutic guy? Sorry, I forgot his name - it was maybe 10 years ago I listened to his speech.

I had a stab at trying to locate the guy and came up empty. I found this instead - it is a Danish study on how people experience infrasound. It is written in Dansish so you will have to rely on translation software if you want to read it. http://docplayer.dk/6609246-En-spoergeskemaundersoegelse-af-klager-over-infralyd-og-lavfrekvent-stoej-endelig-rapport-moeller-henrik-lydolf-morten.html

/C

Javi, I am not an expert in the field of sound and biology. However, I do know that our physiology has evolved in adapting to the environment, and that there are sounds in our niches, both internal and external. With regard to the internal sounds, there are at least two groups studying the sounds that cells generate, for example. So in a systematic approach to what you are trying to achieve, I would think that determining the normal sounds made by cells and how they interact with the sounds in the environment would be the interface you seem to being looking for? Like Hols't "The Music of the Spheres", biologic beings strive to be in harmony with their environment, which is what you're seeking, if I may.

I tend to hear a "cosmic-like sound" when I meditate or there is little noise. What could it be?

The individual and public health hazard aspects of infrasound have been extensively researched. The hazards have been specifically linked to frequencies and amplitudes that were explicitly identified. Perhaps such hazards overshadow the healing effects. It is reported that every human being's metabolism uses body-generated infrasound for normal health. So it is quite plausible that future research can identify specific spectral characteristics of infrasound that heal.