Harmonics and InfraSound

Question

Hey everyone,

So this is my first time asking a question. So here is the setup. I'm currently in pre-production of a film in which I am doing both production and post audio. It is a thesis film in which the director wants to maintain a certain tension similar to horror films. A key audio part is a low end hum that resonates in and throughout the characters apartment. Its not a horror film but more of a psychological thriller. So Ive been doing research and came across this page.

http://www.cracked.com/article_18828_the-creepy-scientific-explanation-behind-ghost-sightings.html

It relates infrasound to many "ghost hauntings"

Cool concept to use in a film, an inaudible note that produces physical anxiety.

Problem is that nothing I have nor any venue has the ability to reproduce tones that Low.

Then I stumbled upon another question here on SSD regarding low end production out of laptop speakers and using the Idea of Missing Fundamental to achieve that.

Low End on Small Speakers http://en.wikipedia.org/wiki/Missing_fundamental

So now to my question. Any idea if using harmonics of infra sounds would produce the same effect? I am leaning towards no because the waves actually shift parts of the body, but there are some psychological effects that may occur, Any thoughts on it?

I do know that I don't need those tones to achieve discomfort but I'm in the process of creating a large palette of different sounds to work with later, and am finally given a chance to work with sound on a pure conceptual level before I even look at a frame of film on a project. And why not explore this avenue, the military has :)

Also I know that I have to be extra careful in the design to not overwork the sub, any ideas, tips, tricks?

Thanks a bunch

Michael Gilbert

Answer 1

The discussion you're referring to is talking about psychoacoustic perception. Our brain CAN fill in the fundamental sound based on the presence of its harmonics, but that capability is closely tied to structure of the harmonics (which are dependent on the source of the sound). Remember, what our brain interprets as sound are electrical signals that have been transduced through our hearing organs. We're really "hearing" analog sound, not acoustic.

The effect you're looking for is going to be next to impossible using that technique for one very specific reason...we don't HEAR those frequencies you're looking to create. Yes, we can sense them, feel them, but it's more a function of our ability to sense equilibrium and external forces acting on our body...it's a physical response. To an extent, it's also resonance within the larger cavities of our body. Our body doesn't have the ability to transduce those pressure waves into an auditory response, and our brain isn't wired to interpret them even if we could. Without that function, you're not going to imply those low frequency tones you're looking for.

EDIT: Quickly looked at the Cracked article, and they got something wrong in there. It's not that your ears "sense" the sounds even though you can't hear them, but there is still pressure from the wave's compression/rarefaction on the ear drum. There are organs and mechanics within the ear that contribute to our perception of equilibrium. Pressure on the timpanum affects those processes in addition to hearing. Large amounts of pressure on the timpanum will mess with your equilibrium, and too much can cause physical damage, whether you can "hear" the pressure wave or not.

Answer 2

I recommend you check out Dr Steve Goodman's book on sonic weapons. Infrasound can be produced artificially (usually by fluke) or naturally at a range that causes tricks of the eyes like ghost sightings or feelings of dread, worry, panic. Vic Tandy was an engineer from coventry that decided to investigate workers worries of hauntings in the lab they worked in. To cut a long story short, a recently installed air vent was causing the infrasound due to not being bolted properly. He checked with scientific measuring equipment that this was causing infrasound waves around areas in the room where sightings were happening including one apparition seen by himself. Tightening the bolt caused all ghost sightings in the building including fears of being watched and general unease to stop immediately. Basically a certain frequency of infrasound can cause the eyeballs to vibrate at a rate which causes us to see things that are not there, the ears have nothing to do with it as we cannot hear these frequencies. In regard to the posted question even if you could reproduce this kind of infrasound on a films sound design I think it would be the wrong thing to do in regards to a viewers well being.

Answer 3

You can also check out the works of Alfred A. Tomatis related to psycho-acoustics and how we learn hearing inside the womb...

http://en.wikipedia.org/wiki/Alfred_A._Tomatis

I read all of his books, there is a lot of information there for somebody who likes to get sound design on the next level.

Cheers!

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