I was reading the thread about recording from 0-20 Hertz and it made me wonder. I know humans can’t hear frequencies that low. But they would still vibrate in your body, yes? Would you just feel pressure or vibrating without knowing where it was coming from? Could this kind of exposure at very high “decibel” levels cause damage to the ears, heart, lungs, or other body parts? Do decibels as a measurement even have a meaning when it comes to non-audible sound?
There was an episode of mythbusters about the “brown note” trying to determine the effects of inaudible low frequency sound on the human body. If I remember correctly, there wasn’t a frequency that could make you lose control of your bowels, but they did seem to feel a bit nauseous afterwards.
See the note at the end of this column: Why is bass so boomy, and what can I do about it? - The Straight Dope
I also see the column has a weird HTML thing in it we’ll have to fix…
I don’t know about other organs, but extremely high dB levels will damage your ears, even if the frequency is inaudible.
I vaguely recall reading something once…I think it was a work of “detective fiction” that “subsonic” sounds could produce a feeling of terror and angst in people that were exposed to them. In this case, the bad guys were using this method to keep people away from their base of criminal operations. If someone got too close and was in danger of spotting the crooks at work, they were suddenly beset by an inexplicable sense of paranoia and panic and usually departed hastily. I have no idea if this has any scientific validity or was just some fiction writers clever daydream. But it’s an interesting idea.
SS
Also, Washington, D.C., police equipped cars with a low-frequency “rumbler” but I never had the treat of experiencing it and don’t know if it’s still in use.
I have thrown an ELF generator through a phased line array of loudspeakers to test the frequency response and throw of the system. Usually you use pink noise, but we had also hooked up an enormous rank of subs.
Two results: blew a number of amps (the power required is pretty massive, even for an arena level system, and at full volume it definitely induced a low grade nausea and general discomfort. Did not actually shit pants, though.
ahh! Some fantastic answers so far 
Very, very awesome.
How does this blow amps (I would have expected it to blow speakers)? IANAEE, but I would think that if an amp can’t provide the power, it just…doesn’t. It’s not like you’re giving it line voltage that is too high. What blows, and what causes it? (If this is too much of a tangent I would be happy to open another thread.)
Here’s a Cracked article that suggests infrasound is a possible explanation for what people perceive as ghosts.
It normally blows the overload protection. Not a fatal error, but needs replacing/resetting depending upon the model.
I’m not sure if it’s heat, or what. Im an audio engineer (studio mostly) and definitely not an EE.
I am wondering if that is an evolutionarly instinctual response. Aren’t earthquakes alway proceeded by low frequency vibrations? And isn’t it documented that animals (usually house pets) start acting freaked out shortly before an earthquake? Of course someone probably already figured this out, but it just occurred to me and makes sense.
Wasn’t that in one of the Three Investigators books I read as a kid? The Terror Castle one, maybe?
Ha! Indeed it was The Secret of Terror Castle. I hadn’t thought of the Three Investigators in lo these 30-odd years, surprised to see they’re still in print and available. Thanks Kolga for the chortle!
SS
Yep, Psychic TV used to play with this back in the day. A guy I know related how he once spent the duration of one PTV concert freaked the fuck out for no particular reason, and only discovered the reason the next day when he heard Genesis P-Orridge talking about their of subsonics.
From personal experience at industrial and doom concerts, as they shift the frequency of the drone you’ll feel different parts of your anatomy (both external and internal) suddenly start and stop vibrating as different resonance frequencies are hit. You can end up pretty nauseous, especially if you have a full stomach. At loud enough volumes, you’ll feel the air slapping your skin.
You make this yourself in some cars. Roll down one window, leaving the rest rolled up. At the right speed, you can get a wump wump wump going, 2 to 3 wumps per second.
The best example was a long time ago, when I had a car with a removable sun roof. With the windows rolled up, at about 35-40 mph, it was unbearable for more than a few seconds.
I think it’s basically the same physics as the note you get when blowing across a bottle opening.
Yes, it is a Helmholtz resonator. Neat idea to get instant infra-bass.