This is a good overview of the topicand the correct conclusion is that it is completely ineffective as apotential weapon and remains a solution in search of a meaningfulproblem. Otherwise good scientific fun and well worth the read.
Even the legend of brown sound isdebunked as non existent and can be tossed into the bins of urbanlegends. Some things are just too good to be true.
Otherwise this is a primer of the topicthat is useful to have seen.
CouldA Sonic Weapon Make Your Head Explode?
Infrasonicsound can have very unusual non-auditory effects on the body. Butdoes it kill?BySeth S. HorowitzPosted 11.20.2012http://www.popsci.com/technology/article/2012-11/acoustic-weapons-book-excerpt
There’san elevator in the Brown University Biomed building (hopefully fixedby now) that I’ve heard called “the elevator to hell,” notbecause of destination but because there is a bent blade in theoverhead fan. The elevator is typical of older models, a box 2 metersby 2 meters by 3 meters with requisite buzzing fluorescent, making ita perfect resonator for low-frequency sounds. As soon as the doorsclose, you don’t really hear anything different, but you can feelyour ears (and body, if you’re not wearing a coat) pulsing aboutfour times per second. Even going only two floors can leave youpretty nauseated. The fan isn’t particularly powerful, but thedamage to one of the blades just happens to change the air flow at arate that is matched by the dimensions of the car. This is the basisof what is called vibroacoustic syndrome—the effect of infrasonicoutput not on your hearing but on the various fluid-filled parts ofyour body.
Peopledon’t usually think of infrasound as sound at all. You can hearvery low-frequency sounds at levels above 88–100 dB down to a fewcycles per second, but you can’t get any tonal information out ofit below about 20Hz—it mostly just feels like beating pressurewaves. And like any other sound, if presented at levels above 140 dB,it is going to cause pain. But the primary effects of infrasoundare not on your ears but on the rest of your body.
Becauseinfrasound can affect people’s whole bodies, it has been underserious investigation by military and research organizations sincethe 1950s, largely the Navy and NASA, to figure out the effects oflow-frequency vibration on people stuck on large, noisy ships withhuge throbbing motors or on top of rockets launching into space. Aswith seemingly any bit of military research, it is the subject ofspeculation and devious rumors. Among the most infamous developers ofinfrasonic weapons was a Russian-born French researcher namedVladimir Gavreau. According to popular media at the time (and far toomany current under-fact-checked web pages), Gavreau started toinvestigate reports of nausea in his lab that supposedly disappearedonce a ventilator fan was disabled. He then launched into a series ofexperiments on the effects of infrasound on human subjects, withresults (as reported in the press) ranging from subjects needing tobe saved in the nick of time from an infrasonic “envelope of death”that damaged their internal organs to people having their organs“converted to jelly” by exposure to an infrasonic whistle.
SupposedlyGavreau had patented these, and they were the basis of secretgovernment programs into infrasonic weapons. These would definitelyqualify as acoustic weapons if you believe easily accessible webreferences. However, when I started digging deeper, I found thatwhile Gavreau did exist and did do acoustic research, he had actuallyonly written a few minor papers in the 1960s that describe humanexposure to low-frequency (not infrasonic) sound, and none of thesupposed patents existed. Subsequent and contemporary papers ininfrasonic research that cite his work at all do so in the context ofpointing out the problems of letting the press get hold of complexwork. My personal theory is that the reason that his work survivedeven in the annals of conspiracy is that “Vladimir Gavreau” isjust such a great moniker for a mad scientist that he had to be up tosomething.
Conspiracytheories aside, the characteristics of infrasound do lend it certainpossibilities as a weapon. The low frequency of infrasonic sound andits corresponding long wavelength makes it much more capable ofbending around or penetrating your body, creating an oscillatingpressure system. Depending on the frequency, different parts of yourbody will resonate, which can have very unusual non-auditory effects.For example, one of the ones that occur at relatively safe soundlevels (< 100 dB) occurs at 19Hz. If you sit in front of a verygood-quality subwoofer and play a 19Hz sound (or have access to asound programmer and get an audible sound to modulate at 19Hz), trytaking off your glasses or removing your contacts. Your eyes willtwitch. If you turn up the volume so you start approaching 110 dB,you may even start seeing colored lights at the periphery of yourvision or ghostly gray regions in the center. This is because 19Hz isthe resonant frequency of the human eyeball. The low-frequencypulsations start distorting the eyeball’s shape and pushing on theretina, activating the rods and cones by pressure rather than light.*This non-auditory effect may be the basis of some supernaturalfolklore. In 1998, Tony Lawrence and Vic Tandy wrote a paper forthe Journal of the Society for Psychical Research (not myusual fare) called “Ghosts in the Machine,” in which theydescribe how they got to the root of stories of a “haunted”laboratory. People in the lab had described seeing “ghostly” grayshapes that disappeared when they turned to face them. Upon examiningthe area, it turned out that a fan was resonating the room at18.98Hz, almost exactly the resonant frequency of the human eyeball.When the fan was turned off, so did all stories of ghostlyapparitions.
Almostany part of your body, based on its volume and makeup, will vibrateat specific frequencies with enough power. Human eyeballs arefluid-filled ovoids, lungs are gas-filled membranes, and the humanabdomen contains a variety of liquid-, solid-, and gas-filledpockets. All of these structures have limits to how much they canstretch when subjected to force, so if you provide enough powerbehind a vibration, they will stretch and shrink in time with thelow-frequency vibrations of the air molecules around them. Since wedon’t hear infrasonic frequencies very well, we are often unawareof exactly how loud the sounds are. At 130 dB, the inner ear willstart undergoing direct pressure distortions unrelated to normalhearing, which can affect your ability to understand speech. At about150 dB, people start complaining about nausea and whole bodyvibrations, usually in the chest and abdomen. By the time 166 dB isreached, people start noticing problems breathing, as thelow-frequency pulses start impacting the lungs, reaching a criticalpoint at about 177 dB, when infrasound from 0.5 to 8Hz can actuallydrive sonically induced artificial respiration at an abnormal rhythm.In addition, vibrations through a substrate such as the ground can bepassed throughout your body via your skeleton, which in turn cancause your whole body to vibrate at 4–8Hz vertically and 1–2Hzside to side. The effects of this type of whole-body vibration cancause many problems, ranging from bone and joint damage with shortexposure to nausea and visual damage with chronic exposure. Thecommonality of infrasonic vibration, especially in the realm of heavyequipment operation, has led federal and international health andsafety organizations to create guidelines to limit people’sexposure to this type of infrasonic stimulus.
Sincedifferent body parts all do resonate and resonance can be highlydestructive, could you build a practical infrasonic weapon bytargeting a specific low-frequency resonance and thus not have tocarry around a heavy amplifier or lock your victim in an elevatorcar? For example, imagine I am a mad scientist (a total stretch, Iknow) who wants to build a weapon using sound to make people’sheads explode. Resonance frequencies of human skulls have beencalculated as part of studies looking at bone conduction for certaintypes of hearing aid devices. A dry (i.e., removed from the body andon a table) human skull has prominent acoustic resonances at about 9and 12kHz, slightly lesser ones at 14 and 17kHz, and even smallerones at 32 and 38kHz. These are convenient sounds because I won’thave to lug around a really big emitter for low frequencies, and mostof them are not ultrasonic, so I don’t have to worry about smearinggel on the skull to get it to blow up. So how about if I just use asonic emitter that puts out two peaks at the two highest resonancepoints, 9 and 12kHz, at 140 dB and wait until your head explodes?Well, it’ll be a while. In fact, it’s not likely to do anythingother than possibly make a nice dry skull shimmy on the desk a bit,and it will do nothing to a live head other than make it turn towardyou to see where that irritating sound is coming from.
Theproblem is that while your skull may vibrate maximally at thosefrequencies, it is surrounded by soft wet muscular and connectivetissue and filled with gloppy brains and blood that do not resonateat those frequencies and thus damp out the resonant vibration like arug placed in front of your stereo speakers. In fact, when a livinghuman head was substituted for a dry skull in the same study, the12kHz resonance peak was 70 dB lower, with the strongest resonancenow at about 200Hz, and even that was 30 dB lower than the highestresonance of the dry skull. You would probably have to use somethingon the order of a 240 dB source to get the head to resonatedestructively, and at that point it would be much faster to just hitthe person over the head with the emitter and be done with it. Sowhile we still cannot use infrasound to defend ourselves againstdangerous severed heads and have not found the "brownsound"that would allow us to embarrass our friends, infrasound can causepotentially dangerous effects on living bodies—as long as you havea very high-powered pneumatic displacement source or operate in avery contained environment for a long time.
Sorryto be a spoilsport about sonic weapons. I’ve always wanted to beable to wire up a couple of speakers in my basement lab and runaround blowing holes in things and chasing away supervillains, butmost sonic weapons are more hype than hyper. Devices such as the LRADexist and make effective deterrents, but even these have pronouncedlimitations. A handheld sonic disruptor will have to wait for somemajor breakthroughs in power source and transducer technologies. Butthe uses of sound in the future probably hold more interestingpromise than the ability to destroy things.
- You can get a similar visual display, called phosphenes, by rubbing your eyes in a dark room.
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