Recently I ran across the term "infrasound" and naturally had to do some research. What I found was quite fascinating. Infrasound is a range of frequencies below that of human hearing. Infrasound can in some cases explain ghosts (the resonant frequency of your eyes is 18hz) as well as the spine chilling feelings that accompany them. Animals use infrasound for communication and may also induce a sense of discomfort or disorientation in man in cases of tigers and lions. It can also be used as a weapon. Unfortuantely, in the quest for the lowest and most powerful bass from car stereos it is becoming possible to create infrasound with exotic car audio equipment which may be more detrimental than people realize. Just thought I would throw this out as an interesting audio topic. Check it out.
This is a new term for me as well.. I have recently taken an interest in frequencies and their psychological impact on humans... This article: is what sparked my interest. One line that really caught my eye was this: "Some theories, although just theories, even suggest that the nazi regime has been in favor of adopting this pitch as standard after conducting scientific researches to determine which range of frequencies best induce fear and aggression."

There are also people that believe that you also hear music/sound with your body, not just your ears... So even though, typically, your ears can only hear between 20 - 20,000 Hz, your body can take in sounds well above and below that range... I have no idea if this is true or not, but it certainly is interesting either way...

Now, on to read about Infrasound......
Interesting, thanks.
Every time I see (hear) some fool in his car with the windows up and the bass booming with a infant or kid in a carseat, I wish child services was there to take the kids away. Infrasonic can be (?) fun at auto shows and demos for the dim witted out there but really has no place in audio, at those levels.

All the best,
The old Viennese standard for A4 was 435Hz which is closer to the 432Hz your article refers too, but now most orchestras and instruments are tuned to A4 440Hz.
Interesting topic. Infrasound is generally considered to be frequencies below 20hz. 20hz was established as the lower threshold of human hearing for, more than anything, practical reasons since this threshold not only varies substantially from individual to individual, but unlike our upper frequency threshold it drops in sensitivity very gradually. Not only are some individuals capable of hearing below 20hz, but most of us do, in fact, sense or feel frequencies well below 20hz. These low frequencies modulate with frequencies which are mathematically related and much higher in pitch. Music is a harmonic soup of fundamental frequencies and harmonics (overtones and undertones) and accuracy in one frequency range affects our perception of other frequency ranges and is one of the reasons that the low frequency performance of speakers is so crucial and affects the midrange where most music occurs.

Re A=440 tuning: once again, the adoption of this standard was mostly for practical reasons. Orchestras would tune to a higher and higher pitch as a means of producing a more brilliant sound to the dismay of singers whose vocal chords would suffer strain from the ever higher tuning. While I would not dispute the idea that a certain pitch to naturally occurring mathematical phenomena might produce a potentially more "harmonious" sound, I think that practically it is much to do about nothing since it is typical for orchestras to take the A (440hz) from the oboe and then within minutes from the start of the piece have the overall pitch be hz above that. This is a result of (in the case of the winds) of the inescapable tendency of the instrument to produce a higher pitch as the instrument warms up, and the natural human tendency for a player to want to hear himself within a large ensemble and a more brilliant sound accomplishes this.