Welcome to tech Stuff, a production from iHeartRadio. Hey Therein Welcome to tech Stuff, I'm your host, Jonathan Strickland. I'm an executive producer with iHeart Podcasts and how the tech are you? So? On Monday's episode of tech Stuff, I covered the topic of active noise canceling headphones or active noise reduction headphones, and I mentioned in that episode the development of a system designed to cause discomfort in young people through the use of sound played at a pitch that most adults can't hear, because as we age, we start to lose the upper range of our hearing. This device is called the mosquito. And while I was a little flippant in the noise canceling episode, the truth is that acoustic weaponry is a thing. It might potentially cause significant heart depending on how it is used. And one of the scariest things about acoustic weaponry is that we don't actually really know how dangerous or not dangerous it is. So today I thought i'd talk a little bit about the history of using sound as a weapon, the technology created to harness sound in such a way, and the scholarship or lack thereof, surrounding the topic. Now On the one hand, sound has undoubtedly been weaponized in the past. You can't deny that sound has been used as a weapon. But on the other hand, there remain many questions as to the efficacy of acoustic weaponry. I guess it depends upon your intent. There's little doubt that someone could use sound to cause irritation or even pain in an effort to say, disperse a crowd. That's been used many times, especially over the last couple of decades here in the United States. There are stories about more sinister weapons, ones that you know, use sound to cause physical trauma up to and including lethal injury to targets. In fact, according to one scholarly article on the subject, one that I'll talk about a lot more in this episode, some stories allege that through sound and acoustic weapon could induce cavitation in tissue. That is, the sound could create bubbles within tissue like your organs, and then those bubbles could implode and that could cause significant damage. Nothing like the thought of, you know, liquefying organs. To really spice up your research now, I think it is very important to add that the scientific paper I just mentioned, it's titled Acoustic Weapons a prospective assessment. It was written by Jurgen Altman, and the author stresses that these are merely allegations. There's a distinct lack of evidence supporting these kinds of claims. Altman makes this very clear. Is a long and thorough article, and I highly recommend you read it. It was originally published in the scientific journal Science and Global Security, volume nine. It originally published in two thousand and one. It is free to read, so if you want to read the whole thing, you should. It's really a good read. I mean, it's actually written in a way that's very accessible. I think. Now, obviously it could be the case that since two thousand and one there have been more scientific focus directed at acoustic weaponry. But doing that is kind of tricky because, for one thing, how do you study potentially traumatic or even deadly effects of sound on human subjects, Because that's not exactly an ethical thing to do. If part of your question is will this hurt someone? If I play this frequency of sound at this volume putting someone in the path of that, that's really questionable, not questionable even I think that's just downright on ethic. Meanwhile, you have folks in the real world building real stuff that is weaponizing sound, So we don't fully understand what effect this could have on people. It may be largely benign apart from the obvious dangers of like hearing loss and stuff, but it might be worse. We just don't know. And meanwhile, we actually have companies making these things and various militaries and law enforcement agencies using them, so it's kind of scary. It's almost like the lack of evidence gives cover to those who are profiting off turning sound into a weapon because there's no proof showing that these weapons can be lethal, right, so they're non lethal weapons. They're not causing real harm, at least that could be the argument. So it should be totally fine for like a police force to use a directed acoustic weapon on a group of students who are testing something on a college campus because it's not lethal. And if you're thinking that sounds incredibly irresponsible and potentially criminal, then you're catching on quick. But let's talk about the history of acoustic weapons. Now. One place that a lot of articles about the history of acoustic weapons are sound as a weapon will pick as their starting point is the biblical account of the Battle of Jericho, which I think is a fun way to start, but not really helpful. But yeah. In the in the Bible, the story is Joshua leads the Israelites to conquer Canaan, and the city of Jericho's on their to do list, and the big guy upstairs tells Joshua that he and his army are to carry the Ark of the Covenant, as featured in the documentary Raiders of the Lost Arc, and they're going to have the procession led by seven priests who are blowing trumpets made of Ram's horn, and they're to do that for six days, going around the city one time each day. On the seventh day, they are to march around the city seven times, blowing the trumpets, and then afterward letting out a big old whoah, you know, shouting out, and at that point the city walls will come a tumblin' down, as Professor Harold Hill would say, now, not to burst any bubbles. But archaeological digs suggest that while there was a city in Jericho's spot before this particular period in history, and there was a city in Jericho's spot after this particular era of history, during the time when the story is actually supposed to have taken place, there were no people living in Jericho. So, in other words, the story's just a story, but it's a fun one to start with. So could sonic blasts actually knock down walls? Well, I would argue that, since this is a biblical story, it's not really like the pressure wave coming from these trumpets knocked the walls down. Rather, it's more like God saying, all right, y'all seem to follow my arbitrary orders I gave you, so now you get to kill everybody in town, which you know that's wild, But yeah, I would argue that the implication here is not that the trumpets knocked down the walls, but rather it was the big deity in charge who did the knock and down part. Still, you can imagine how sound could play a part in war. You could use sound in order to convey signals across distance. You could use sound in an attempt to intimidate the enemy. There's the infamous scene in Apocalypse Now in which a fleet of helicopters are blasting Wagner's Ride of the Valkyries as they fire down upon Viet Cong soldiers and Vietnamese civilians alike. So there's that now, Granted, that's fiction and people will tell you that didn't really happen, but that's a popular media depiction of using sound and warfare. Scottish bagpipes have been used for the purposes of kind of intimidating foes, as anyone who has heard them up close inevitably wants to find a way to get away from that point really quickly. I'm joking, kind of fun. Sign note, there's a bit of lore in bagpiping that the British actually outlawed the playing of bagpipes in Scotland around seventeen forty five as part of a larger disarming act, because bagpipes have been deemed an instrument of war literally in this case. But historian John Gibson, in his book Traditional Gaelic Bagpiping seventeen forty five to nineteen forty five, argues that the text of this disarmament Act does not actually name bagpipes as being prohibited, and that pipers who bring up this era of supposed persecution are probably just tired of people asking if they could kindly stop that awful racket. I'm having a lot of fun here, but I think it's only fair to say I actually kind of like bagpipe music. Anyway, Sounds played an important role in warfare, but that's not the same thing as using sound as an actual weapon. Now, according to Yurigen Altman's research, there's not much on record of militaries using sound as a weapon of war, though he did find suggestions that both Japan and the United Kingdom looked into the possibility of using acoustic weapons to lethal effect over some distance. Now. According to that research, both countries ultimately came to the conclusion that if it were in fact possible to create a sound so strong as to be lethal, it would require more power than would be practical. It would make way more sense to, you know, just use the conventional weapons we already have at our disposal. Why would you go and build this thing to get the same result you would get from weapons we already have. Which makes me think of Jurassic World. So big spoiler for the Jurassic World series, although I have a low opinion of those movies anyway, one of the plot points in that series is that the military wants to make use of dinosaurs, essentially using them to be like beasts of war and using lasers to point at enemies and then the dinosaurs attack the lasers because they've been trained to do that. But you know, we've got stuff like guns with laser sights or bombs and missiles with laser guidance. So it seems like it's an unnecessary and and practical use of our time and resources. Anyway, let's get back to sound. Altman's research included a nineteen sixty nine book titled Riot Control Material and Techniques by Our Applegate. Now. The book mentioned that many scientific articles had discussed the use of acoustic weapons in a non lethal capacity, specifically using low frequency sounds to counter, say a riot. Now, Altman points out that he was unable to find evidence of the mentioned scientific articles. He said, if these articles exist, I couldn't find them. The book alleges they exist, but I don't know where. According to Applegate, whomever it was that looked into using devices to create this low frequency sound to make this effect to do riot control ultimately determined it would be too expensive to be practical. Now, some of that makes sense, because I'm going to talk more about sound waves and frequencies and wavelengths and stuff later in this episode. But if you're talking about low frequencies like below, the threshold of typical human hearing, which at the low end is around twenty hurts. If you're talking about below that, well, the sound waves you're talking about are long. Those wavelengths are pretty long. You're talking about a low frequency and long wavelengths. High frequency have shorter wavelengths. With those long wavelengths, you also need a large loud speaker in order to actually produce those wavelengths. If you've ever seen the speakers on a stereo system, you know you've got different types, right, You've got your tweeters, you've got your subwiffers, that kind of thing. Well, the speakers responsible for the higher pitches are going to be smaller. The diaphragm needed to push air around to create those higher frequency sounds is smaller and needs to move very quickly in order to do that. The base speaker is going to be much larger, and it's going to move more slowly in order to push the air properly to create those low frequencies. So, if you want to create a really powerful, very low frequency generator, it's going to be huge and it's going to require a lot of power to move that massive diaphragm, especially if you want to do so at a really high amplitude, as in a really high volume, that just is going to require an enormous amount of energy, which is I think one of the reasons why even if militaries did look at infra sound as a potential weapon, they ultimately came to the conclusion that it was impractical because you would have to build things that are so large and so power or energy hungry that it just didn't make sense like you could achieve the same effect through other means without spending all that time and effort and energy to operate an impractical weapon. So sound did become important when it was playing a part in you know, like psychological operations aka SYOPS. I feel like I should get the stuff. They don't want you to know, guys on here to talk about syops because that's kind of right in their sweet spot. But this gets back to the concept of using sound in an effort to intimidate the enemy. So while Apocalypse Now was a fictional use of sound to get the sort of achievement, there are real world analogs that used sound or attempted to use sound in ways to get a very similar result. So, for example, during the Vietnam War, our US forces used recorded sounds in an attempt to demoralize Viet Cong soldiers. One such operation was called Wandering Soul, and this hinged on Vietnamese culture. So in Vietnam there was a widely held belief. This is widely held belief that if someone dies and they do not receive a proper burial, their spirit would be forced to wander the earth in pain for all eternity. So the US started blasting a spooky recording of South Vietnamese people impersonating deceased Viet Cong soldiers, the ghosts of Viet Cong soldiers who apparently were consigned to this fate. Some of the recordings included messages urging soldiers to return home to their families and to abandon the fight. Now, the effectiveness of this campaign is questionable, as it's pretty hard to conceal the fact that a helicopter is blasting out a recorded message as opposed to just believing there's an actual ghost jamboree going on outside. And nineteen seventy the US had stopped using this tactic in Vietnam, but it was an attempt to use sound to intimidate. I'll talk more about the exploration of acoustic weapons. But first, let's take a quick break to think our sponsors. All right, let's get back to Jurigen Altman's work. He did find some other instances of acoustic weapons in scholarly journals, though tracking down any hard evidence that any of these things were ever built and or used was a totally different story. But one such instance involved a supposed device created by the British Army in an effort to deal with protesters in Northern Ireland. The device, nicknamed the squawk Box, produced two high pitch frequencies within the range of typical human hearing, although if you're old enough you wouldn't pick up bottom inherently. One of the pitches was at sixteen killer hurts and the other was at sixteen point zero zero two killer hurtz. I probably wouldn't be able to hear these my hearing tops out somewhere in the fifteen to sixteen killer hurtz range, at least the last time I tested it. That's where it was, so I might not perceive this directly at all. However, at high amplitudes, at high volumes, these higher pitch frequencies can interact with one another and interfere with one another. When we talked about noise canceling headphones, I talked about how this works in that context, where you create a sound wave that's in opposite to the one that you're trying to block, and if you're doing that, the two waves cancel each other out and you get silence or near silence as a result. So the production of these two different frequencies would induce a third frequency to form within the ears of protesters, and the effect was supposedly so so intense that people couldn't withstand it. They had to get away from the sound. Altman points out that the UK has denied that such a device has ever existed, and he also mentions another source that concluded that while the British may have looked into actually making such a thing, it may never have been built. So it sounds like this is another one of those things where people said, you know, this should be able to work, but no one actually made the thing. But it does come into play when we get to audio spotlights a little later in this episode, so that's a fun little tidbit. Further, Altman writes about articles claiming that infrasound you know below the typical range of human hearing, so below that twenty Hurtz range, played at a high enough volume, like at around one hundred decibels, can disorient the listener. But Altman's research also came across scientists who said they could not confirm these findings, so whether that's actually true or not remains unknown. It's kind of funny because you know, this is an anecdote, so it's not really it's not evidence at all. But this is something that happened to me not too long ago. I was in a car with my partner and a jeep pulled up behind us, and the person in the jeep had their sound system blasting at an incredible volume, and the bass was cranked up, probably about as far as it could go, And even though we were sitting in a car with our windows rolled up, we could hear that bass pretty clearly, and it did create a rather unpleasant and disorienting sensation, though that might just be because I'm old and cranky and have nothing to do with any physiological reason. Altman specifically states that his research focused on acoustic weapons that are intended to do physical damage to a target, rather than just using sound as a way to annoy or distress someone by you know, like preventing them from getting rest, for example, which is legit. But I think we should take the use of sound as a deterrent or way of distressing someone into consideration, because while there is a lack of firm scholarship on the efficacy of sound as a weapon that causes direct physical harm or perhaps even death, we do have plenty of examples of folks using sound to make someone else's life more difficult. For example, Christmas nineteen eighty nine, five years after the song do they Know It's Christmas? Came out? Now, I think there's no denying that that particular song is torture all by itself, but it doesn't factor into the story now. In nineteen eighty nine, the US military used rock and or roll music to force Manuel Noriega to exit the Vatican embassy in Panama City, at least that was their intent. So the US won in Noriega on charges of drug trafficking and such, and Noriega had sought refuge in the embassy. So the US put some really powerful speakers on hum v's, drove the humv's around the embassy, and blasted the embassy with tunes like I thought the Law by the Clash, which is classic, or all I what is you by you too? And because the military really does have a six sense of humor Hanama by Van Halen. But mostly they played a lot of songs by guns n' Roses and the Doors. This musical assault lasted three days, but then the Pope called the President and said, hey, can y'all knock it off please? That's our embassy. And the US complied, and Noriega ultimately surrendered himself just a few days later. I don't know, maybe he missed the music. In nineteen ninety three, law enforcement agents employed the let's blast them with sound technique on David Koresh's compound in Waco, Texas. This is the infamous Branch Davidian holdout. Now. Among the sonic bombs that they dropped were various songs as well as the sound of jet planes and disturbingly, one report said, the screams of rabbits as they were being slaughtered. Yikes. Now the military has used loud music to rock the sleep and morale of prisoners of war as well, in order to soften them up for interrogation or break down their resistance by preventing them from getting enough rest, so mentally they wouldn't be able to withstand interrogation techniques. Now, I find all of this ethically troubling, to say the least, particularly in light of research that has suggested repeatedly that torture is not effective. At least, it's not effective if your goal is to get at some sort of truth, no matter how popular media might suggest otherwise. I'm looking at you, Jack Bauer, But I mean, I guess you could argue it is effective if your only goal is to make the tortured person feel miserable and powerless. Yeah, it works to that extent, but that seems you know, repugnant. You know, again, not really the same as using a weapon of war. So what about l rads l RAD That initialism stands for long range acoustic device, and in turn these actually evolved from an earlier device, the AHD or acoustic hailing device. All right, this involves a pretty tragic story. So back in two thousand, US forces aboard a Navy destroyer named the USS Coal were attacked when terrorists aboard a small boat approached the vessel and then bombed the destroyer. The attack killed more than a dozen US service members as a result. As the boat was approaching, the USS Coal attempted to hail the vessel to determine the crew's intent, but they got no response. There was no radio contact with the boat, so hailing involved using loudspeakers to send out a message over the water. But sound doesn't travel forever. As I mentioned in Monday's episode, over distance, sound waves attenuate they diminish in strength, so it was reasonable to assume that the crew on the smaller boat just couldn't hear the messages. Once the boat was close enough that those aboard the USS Coal could be sure that they were being heard, it was already too late, and the attack immediately followed. One consequence of this attack was that engineers began to develop technology designed to focus sound waves and to blast them out at high enough amplitude or volume so that intelligible sound could travel much, much further in a directed fashion. This was the acoustic hailing device, and it would allow naval forces to send an audible message, not just audible, but intelligible, as in you can understand what someone is saying, in order to warn approaching craft that they need to make their intent clear and follow orders or else potentially face defensive measures from the Navy. Essentially, the Navy would be able to say stop where you are, or we will shoot you now. To accomplish this, the device needed to be able to one blast out sound with enough energy enough amplitude to travel a far distance, and two focus that energy toward the target. And turns out you can do this with sound. So let's talk about sound beams or audio spotlights, because this is really cool. All right. So I mentioned in the previous episode that sound travels in waves, in longitudinal waves. Actually we talked about that in the active Noise Canceling episode, but these waves are pretty darn long. So I'm talking about the wavelengths of sound that are within the typical range of human hearings, so between twenty hurts to twenty killer herts. If you compare those wavelengths to like light waves sound waves in the audible range, they are enormous. And that link means that sound waves can and do bend around physical objects. They diffract. So here's a way of imagining this. Let's say you're standing on one side of a free standing opaque wall. Let's say the wall is like eight feet tall. I'm on the other side of this opaque wall. We would still be able to talk to each other, right, You could speak and I could hear you, and I could speak and you could hear me, even though there's a wall in the way and we can't see each other. Well, the light is not able to diffract around the height of the wall. The light wavelengths are so small they don't diffract around this wall. But the sound waves are long enough where they can diffract around the wall. Otherwise, if they couldn't, we would speak and the sound would just not be able to cross the wall. It would go in every other direction and we wouldn't be able to hear one another. But we know that's not the case. We know we would be able to hear each other. If light did that, by the way, it would be almost like we have X ray vision, But it doesn't work that way. That same feature, however, this long wavelength of sound makes it very hard to focus sound into a beam. Sound on its own would just travel outward from the source essentially in all directions and lose energy as it travels, or, if you prefer, the energy disperses as the sound travels outward from the source. So as you go further away from where the sound was made, it gets less audible until you get to a point where you just can't detect it at all. So how do you make sure sound is audible from very far away? Well, one way is you could just keep upping the amplitude, but that gets dangerous. Also, it would get to a point where it's so loud that everyone near the audio device would need some serious air protection, and even then there's some worry about how those vibrations would affect the human body. Keep in mind that sound through a gaseous medium is essentially changes in air pressure, and if you're blasting stuff out at like one hundred and sixty decibels, that's massive amounts of air pressure, Like it would feel like you're getting punched. Now, remember the decibel scale is also logarithmic. This is something that's hard to get your mind wrapped around unless you deal with logarithms all the time, in which case it's easy, but I think for most people it's not intuitive. So if you have a sound that's ten decibels, that means that it's ten times louder than something that's at zero decibels. Zero decibels is a sound that is barely audible. If you are talking about a sound that's at twenty decibels, twenty decibels is one hundred times louder than zero decibels. So once you get up to around one hundred and twenty decibels, you're talking about sound that's loud enough to cause permanent hearing damage or hearing loss. Once you get a little higher, you're talking about sound that's above the pain threshold. That'd be around one hundred and forty decibels or so l rads can go up to one hundred sixty decibels. That's pretty serious stuff. So it would be great if you could direct sound in a significant way, one to focus that sound, and two to prevent the sound from freaking havoc on your own side. And one way to do that is through what is called an audio spotlight, which emits sound at very very high frequencies, frequencies that are much too high for humans to be able to hear them. In fact, they're too high for dogs to hear them. Cats could probably hear them, Bats definitely could, but not so much with people. I'll explain more after we take this quick break before the break, I was talking about audio spotlights. What is an audio spotlight. It's a surface over which there are are hundreds of transducers that are capable of emitting sound. And at these frequencies, the sound wave links are much smaller than in what's in our audible range, So we're talking about things like in the say sixty five kilohertz frequency. So these transducers, they're like very tiny little speakers that are able to move super fast and super powerful, Like they don't have to be that strong because they're smaller, so you don't use as much energy to move the speaker in order to generate sound. But they are very very tiny, and because the wavelengths that they are generating are also really tiny, they aren't as affected by diffraction, So like this is something that acts more like lightwood than audible sound. So you wouldn't necessarily be able to pick up these very high frequencies if there were a wall in the way, because the sound waves are so small that they wouldn't wrap around the top of the wall and you wouldn't be able to detect them on the other side. However, it also means that the sound will travel in a much more focused way. You can direct the sound toward a target, But if you're generating sounds that are well above the range of human hearing, what good does that do? Right? Like, yeah, we can shoot a beam of sound waves using this focused approach, using very very very tiny sound waves, but if you can't perceive them directly, then what good does that do? Well? It turns out you can create actual audit sounds using these higher frequencies, because again, sound waves at high enough amplitude will interfere with one another. At low amplitude, they'll just pass through each other, but at high amplitude they will interfere. So again I talked about how noise canceling headphones creates destructive interference by creating an anti phase sound that will cancel out incoming sound. But it's also true that if you play slightly different ultrasonic frequencies, their interaction with one another can create frequencies that are actually in the audible range. I mentioned that supposed project that the Ministry of Defense of the UK did in order to dissuade protesters in Northern Ireland, and of course the Ministry of Defense said they never built that thing. But since those days we have had people build audio spotlights, and they work on essentially the same principle. You generate these different frequencies, maybe even the same frequency, just out of phase, and through that you can encode information on top of this frequency, and that information can be within the audible range. So the audio is not coming or the audible audios not coming from the speakers themselves. Right, if you were able to just isolate them playing a single frequency, you still wouldn't hear anything, even though the transducers would be generating sound, it would just be beyond our capability of sensing it. But the interaction of the sound waves themselves creates the audible sound. It's incredible. It's a really neat phenomenon. There's actually a great demonstration of this on YouTube. The channel I saw it on was NPS Physics. The videos title is audio Spotlight How a audio spotlight works. That's their grammatical error, not mine. It's actually taken from a lecture given by doctor Bruce DeNardo, and it's really entertaining. He's a great lecturer. He's very good at explaining how this works at a very high level. Does explain it's much more complicated than he's letting on. But that he's giving kind of the basic explanation of what's happening, and they do use the music of the Eagles in their demonstration. Now I happen to share the same opinion as the dude from The Big Lebowski on that particular band, except for Journey of the Sorcerer, which I think is an awesome instrumental track, and anyone who's familiar with Hitchhiker's Guide through the Galaxy is probably gonna dig it anyway. Using this method, it is possible to direct sound, and with acoustic haaling devices, the intent is to make that sound intelligible so that oncoming vessels can hear commands to stop or whatever, or to turn around. But you can also use the same capability to blast noise that is unpleasant or unsettling and that segues into the long range acoustic devices or lriads. These are not necessarily meant for haling purposes, but for stuff like crowd dispersal, and there are questions as to whether or not it is ethical to use them, or should even be legal to use them. There have been cases in which US law enforcement have used lrad's l rads for crowd control, blasting out a siren noise that's usually projecting sound between two and four killer hurts. Two killer hurts to four killer hurts. That is, that range is fairly high pitched, and it's unpleasant, especially at very high volumes. It's this piercing siren kind of sound, and if it's blasted at you loud enough, it's probably going to cause at least discomfort. And as I mentioned earlier, if the amplitude is high enough, like if you have a decibel level of around one hundred and twenty or more, and these things are capable of much more than that, then you could experience hearing loss just from relatively short exposure to these things. Of course, you could protect yourself with hearing protection, which actually works pretty darn well. That's another reason why a lot of militaries have abandoned the use of acoustic weapons, because if your enemy has ear protection, then your weapon isn't any good. It doesn't work so great. Hearing protection will reduce the decimal level enough so that it's at safe levels. It still probably won't sound great. You'll still get some of that siren noise in, but you wouldn't be in as much risk of experiencing actual hearing loss as a result of that. According to musicology now dot org, the most powerful acoustic healing devices are capable of transmitting audible sound from a distance of more than five kilometers, though most are meant for much shorter distances, like in the five hundred meter range. But don't get me wrong. Five hundred meters is still pretty darn far. I mean, that's more than five American football fields, So that's a pretty darn good distance to be able to transmit intelligible sound to a target. And as mentioned, we still don't really have a full understanding of what this effect could have on people. Jurgen Altmann research suggests that folks have made a lot of assumptions without much hard evidence to back those assumptions up. But that doesn't mean the assumptions are entirely wrong. It means that we can't be sure one way or the other without further study. And study is difficult because if the work could potentially harm your subjects, that's a huge problem. So can infra sound, you know, those very low frequency sounds below the range of human hearing. Can it at a high enough volume at enough decibels cause stuff like nausea or intestinal pain. Could it cause the dreaded brown noise, as in a sound frequency that, when played at a high enough volume, forces you to evacuate, to defecate, in other words, to poop yourself. There's no evidence of that, By the way, doesn't mean it can't happen. I just mean there's no evidence. So could it cause actual physical trauma? If you were blasting sound at like, you know, one hundred and fifty decibels, let's say it's inaudible sound. Maybe it's too low to hear. Could that very low sound at one hundred and fifty decibels cause physical harm Could it resonate with your internal organs causing them to vibrate with enough energy to hurt you. A resonance, I mean, is a thing. The classic example of resonance is you tap a crystal glass, like a champagne glass made out of crystal, and you're gonna hear it ring out a tone. Actually it rings out several tones. You get your base tone and then the harmonics of that tone, but the harmonics have less energy than your primary tone does. Anyway, if you were to play back that same base tone, that would induce the crystal champagne glass to start vibrating. It would vibrate along with this frequency you're blasting it at, if it was the resonant frequency. If it's the same frequency that generates when it when you tap it, if you blast that glass with enough volume of that tone, then it will cause the glass to deform to the point where it will shatter. So this is the class like opera singer causes glass to break using their voice trick. It's actually pretty hard to do for most singers. Usually you would need a pretty significant amount of amplification as well as incredibly good pitch to manage. It can be done, but usually it requires amplifications. It's very hard to do with your voice alone anyway. It's not just champagne flutes made of crystal that resonate. So the thought is that if you dialed an audio emitter to the right frequency, one that's low enough to penetrate the body and strong enough to really get things moving around in there, you can make a person's inerds or their air cavities inside their body vibrate. That would cause that tissue to heat up. Right. Vibration is energy, and it's like friction essentially, kind of the same way microwaves end up heating up food when you put them in the microwave, so of course that's using microwave radiation per of the electromagnetic spectrum, not acoustic waves. But I think we can all agree that having your organs all start to heat up is bad, or maybe induce air bubbles to form inside tissue that's also really bad. But as Altman points out repeatedly, there just is an evidence that this actually happens or has happened, just that there are a lot of articles that hypothesize maybe it could happen, So maybe it would, maybe it wouldn't. Finding out would require deeply unethical research and a cruel disregard for human safety or animal safety, as it turns out, and it might mean that the technology necessary to carry out such an effect would be prohibitively expensive to build and or operate if you did try to do this. So I guess that's good news. Altman's article, as I mentioned, it's free to read. I recommend going through it. It is quite long, and Alman really did his work trying to track down reputable research on the topic. The paper is longer than sixty pages, but again very easy to understand. So if you have time, check it out. That article that is really the basis for a lot of what this episode is all about, although again I went off book for the stuff that was about disrupting someone's sleep cycles or whatever. The article again, its title is Acoustic Weapons a Prospective Assessment. It's in Science and Global Security, Volume nine, two thousand and one, so check that out. Anyway, Acoustic weapons remain a thing. I still think it's really scary that we have these things that are in active use and we don't have a full understanding of the effects of that technology and how harmful they may or may not be. It may turn out that they're relatively not harmful at all, as long as your exposure to them isn't too long. But it could also turn out that they cause some pretty gnarly effects. There's the whole havana syndrome thing that I didn't get into. I'm sure the stuff they don't want you to know. Crew has done an episode on the havana syndrome. I'll have to reach out to them to make sure, but it would be weird if they hadn't. Anyway, I hope that you found this episode interesting. I hope you go check out that article. Read up on this subject, Read up on acoustic spotlights. Those things are cool. What a neat way to create this effect, Like to be able to use sound that's not in our audible spectrum to create audible sounds at a point in the distance. That's just incredible to me, Like it's phenomenal. It blows my mind. In the meantime, I hope all of you out there are doing well and I will talk to you again really soon. Tech Stuff is an iHeartRadio production. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.

Welcome to tech Stuff, a production from iHeartRadio. Hey Therein Welcome to tech Stuff, I'm your host, Jonathan Strickland. I'm an executive producer with iHeart Podcasts and how the tech are you? So? On Monday's episode of tech Stuff, I covered the topic of active noise canceling headphones or active noise reduction headphones, and I mentioned in that episode the development of a system designed to cause discomfort in young people through the use of sound played at a pitch that most adults can't hear, because as we age, we start to lose the upper range of our hearing. This device is called the mosquito. And while I was a little flippant in the noise canceling episode, the truth is that acoustic weaponry is a thing. It might potentially cause significant heart depending on how it is used. And one of the scariest things about acoustic weaponry is that we don't actually really know how dangerous or not dangerous it is. So today I thought i'd talk a little bit about the history of using sound as a weapon, the technology created to harness sound in such a way, and the scholarship or lack thereof, surrounding the topic. Now On the one hand, sound has undoubtedly been weaponized in the past. You can't deny that sound has been used as a weapon. But on the other hand, there remain many questions as to the efficacy of acoustic weaponry. I guess it depends upon your intent. There's little doubt that someone could use sound to cause irritation or even pain in an effort to say, disperse a crowd. That's been used many times, especially over the last couple of decades here in the United States. There are stories about more sinister weapons, ones that you know, use sound to cause physical trauma up to and including lethal injury to targets. In fact, according to one scholarly article on the subject, one that I'll talk about a lot more in this episode, some stories allege that through sound and acoustic weapon could induce cavitation in tissue. That is, the sound could create bubbles within tissue like your organs, and then those bubbles could implode and that could cause significant damage. Nothing like the thought of, you know, liquefying organs. To really spice up your research now, I think it is very important to add that the scientific paper I just mentioned, it's titled Acoustic Weapons a prospective assessment. It was written by Jurgen Altman, and the author stresses that these are merely allegations. There's a distinct lack of evidence supporting these kinds of claims. Altman makes this very clear. Is a long and thorough article, and I highly recommend you read it. It was originally published in the scientific journal Science and Global Security, volume nine. It originally published in two thousand and one. It is free to read, so if you want to read the whole thing, you should. It's really a good read. I mean, it's actually written in a way that's very accessible. I think. Now, obviously it could be the case that since two thousand and one there have been more scientific focus directed at acoustic weaponry. But doing that is kind of tricky because, for one thing, how do you study potentially traumatic or even deadly effects of sound on human subjects, Because that's not exactly an ethical thing to do. If part of your question is will this hurt someone? If I play this frequency of sound at this volume putting someone in the path of that, that's really questionable, not questionable even I think that's just downright on ethic. Meanwhile, you have folks in the real world building real stuff that is weaponizing sound, So we don't fully understand what effect this could have on people. It may be largely benign apart from the obvious dangers of like hearing loss and stuff, but it might be worse. We just don't know. And meanwhile, we actually have companies making these things and various militaries and law enforcement agencies using them, so it's kind of scary. It's almost like the lack of evidence gives cover to those who are profiting off turning sound into a weapon because there's no proof showing that these weapons can be lethal, right, so they're non lethal weapons. They're not causing real harm, at least that could be the argument. So it should be totally fine for like a police force to use a directed acoustic weapon on a group of students who are testing something on a college campus because it's not lethal. And if you're thinking that sounds incredibly irresponsible and potentially criminal, then you're catching on quick. But let's talk about the history of acoustic weapons. Now. One place that a lot of articles about the history of acoustic weapons are sound as a weapon will pick as their starting point is the biblical account of the Battle of Jericho, which I think is a fun way to start, but not really helpful. But yeah. In the in the Bible, the story is Joshua leads the Israelites to conquer Canaan, and the city of Jericho's on their to do list, and the big guy upstairs tells Joshua that he and his army are to carry the Ark of the Covenant, as featured in the documentary Raiders of the Lost Arc, and they're going to have the procession led by seven priests who are blowing trumpets made of Ram's horn, and they're to do that for six days, going around the city one time each day. On the seventh day, they are to march around the city seven times, blowing the trumpets, and then afterward letting out a big old whoah, you know, shouting out, and at that point the city walls will come a tumblin' down, as Professor Harold Hill would say, now, not to burst any bubbles. But archaeological digs suggest that while there was a city in Jericho's spot before this particular period in history, and there was a city in Jericho's spot after this particular era of history, during the time when the story is actually supposed to have taken place, there were no people living in Jericho. So, in other words, the story's just a story, but it's a fun one to start with. So could sonic blasts actually knock down walls? Well, I would argue that, since this is a biblical story, it's not really like the pressure wave coming from these trumpets knocked the walls down. Rather, it's more like God saying, all right, y'all seem to follow my arbitrary orders I gave you, so now you get to kill everybody in town, which you know that's wild, But yeah, I would argue that the implication here is not that the trumpets knocked down the walls, but rather it was the big deity in charge who did the knock and down part. Still, you can imagine how sound could play a part in war. You could use sound in order to convey signals across distance. You could use sound in an attempt to intimidate the enemy. There's the infamous scene in Apocalypse Now in which a fleet of helicopters are blasting Wagner's Ride of the Valkyries as they fire down upon Viet Cong soldiers and Vietnamese civilians alike. So there's that now, Granted, that's fiction and people will tell you that didn't really happen, but that's a popular media depiction of using sound and warfare. Scottish bagpipes have been used for the purposes of kind of intimidating foes, as anyone who has heard them up close inevitably wants to find a way to get away from that point really quickly. I'm joking, kind of fun. Sign note, there's a bit of lore in bagpiping that the British actually outlawed the playing of bagpipes in Scotland around seventeen forty five as part of a larger disarming act, because bagpipes have been deemed an instrument of war literally in this case. But historian John Gibson, in his book Traditional Gaelic Bagpiping seventeen forty five to nineteen forty five, argues that the text of this disarmament Act does not actually name bagpipes as being prohibited, and that pipers who bring up this era of supposed persecution are probably just tired of people asking if they could kindly stop that awful racket. I'm having a lot of fun here, but I think it's only fair to say I actually kind of like bagpipe music. Anyway, Sounds played an important role in warfare, but that's not the same thing as using sound as an actual weapon. Now, according to Yurigen Altman's research, there's not much on record of militaries using sound as a weapon of war, though he did find suggestions that both Japan and the United Kingdom looked into the possibility of using acoustic weapons to lethal effect over some distance. Now. According to that research, both countries ultimately came to the conclusion that if it were in fact possible to create a sound so strong as to be lethal, it would require more power than would be practical. It would make way more sense to, you know, just use the conventional weapons we already have at our disposal. Why would you go and build this thing to get the same result you would get from weapons we already have. Which makes me think of Jurassic World. So big spoiler for the Jurassic World series, although I have a low opinion of those movies anyway, one of the plot points in that series is that the military wants to make use of dinosaurs, essentially using them to be like beasts of war and using lasers to point at enemies and then the dinosaurs attack the lasers because they've been trained to do that. But you know, we've got stuff like guns with laser sights or bombs and missiles with laser guidance. So it seems like it's an unnecessary and and practical use of our time and resources. Anyway, let's get back to sound. Altman's research included a nineteen sixty nine book titled Riot Control Material and Techniques by Our Applegate. Now. The book mentioned that many scientific articles had discussed the use of acoustic weapons in a non lethal capacity, specifically using low frequency sounds to counter, say a riot. Now, Altman points out that he was unable to find evidence of the mentioned scientific articles. He said, if these articles exist, I couldn't find them. The book alleges they exist, but I don't know where. According to Applegate, whomever it was that looked into using devices to create this low frequency sound to make this effect to do riot control ultimately determined it would be too expensive to be practical. Now, some of that makes sense, because I'm going to talk more about sound waves and frequencies and wavelengths and stuff later in this episode. But if you're talking about low frequencies like below, the threshold of typical human hearing, which at the low end is around twenty hurts. If you're talking about below that, well, the sound waves you're talking about are long. Those wavelengths are pretty long. You're talking about a low frequency and long wavelengths. High frequency have shorter wavelengths. With those long wavelengths, you also need a large loud speaker in order to actually produce those wavelengths. If you've ever seen the speakers on a stereo system, you know you've got different types, right, You've got your tweeters, you've got your subwiffers, that kind of thing. Well, the speakers responsible for the higher pitches are going to be smaller. The diaphragm needed to push air around to create those higher frequency sounds is smaller and needs to move very quickly in order to do that. The base speaker is going to be much larger, and it's going to move more slowly in order to push the air properly to create those low frequencies. So, if you want to create a really powerful, very low frequency generator, it's going to be huge and it's going to require a lot of power to move that massive diaphragm, especially if you want to do so at a really high amplitude, as in a really high volume, that just is going to require an enormous amount of energy, which is I think one of the reasons why even if militaries did look at infra sound as a potential weapon, they ultimately came to the conclusion that it was impractical because you would have to build things that are so large and so power or energy hungry that it just didn't make sense like you could achieve the same effect through other means without spending all that time and effort and energy to operate an impractical weapon. So sound did become important when it was playing a part in you know, like psychological operations aka SYOPS. I feel like I should get the stuff. They don't want you to know, guys on here to talk about syops because that's kind of right in their sweet spot. But this gets back to the concept of using sound in an effort to intimidate the enemy. So while Apocalypse Now was a fictional use of sound to get the sort of achievement, there are real world analogs that used sound or attempted to use sound in ways to get a very similar result. So, for example, during the Vietnam War, our US forces used recorded sounds in an attempt to demoralize Viet Cong soldiers. One such operation was called Wandering Soul, and this hinged on Vietnamese culture. So in Vietnam there was a widely held belief. This is widely held belief that if someone dies and they do not receive a proper burial, their spirit would be forced to wander the earth in pain for all eternity. So the US started blasting a spooky recording of South Vietnamese people impersonating deceased Viet Cong soldiers, the ghosts of Viet Cong soldiers who apparently were consigned to this fate. Some of the recordings included messages urging soldiers to return home to their families and to abandon the fight. Now, the effectiveness of this campaign is questionable, as it's pretty hard to conceal the fact that a helicopter is blasting out a recorded message as opposed to just believing there's an actual ghost jamboree going on outside. And nineteen seventy the US had stopped using this tactic in Vietnam, but it was an attempt to use sound to intimidate. I'll talk more about the exploration of acoustic weapons. But first, let's take a quick break to think our sponsors. All right, let's get back to Jurigen Altman's work. He did find some other instances of acoustic weapons in scholarly journals, though tracking down any hard evidence that any of these things were ever built and or used was a totally different story. But one such instance involved a supposed device created by the British Army in an effort to deal with protesters in Northern Ireland. The device, nicknamed the squawk Box, produced two high pitch frequencies within the range of typical human hearing, although if you're old enough you wouldn't pick up bottom inherently. One of the pitches was at sixteen killer hurts and the other was at sixteen point zero zero two killer hurtz. I probably wouldn't be able to hear these my hearing tops out somewhere in the fifteen to sixteen killer hurtz range, at least the last time I tested it. That's where it was, so I might not perceive this directly at all. However, at high amplitudes, at high volumes, these higher pitch frequencies can interact with one another and interfere with one another. When we talked about noise canceling headphones, I talked about how this works in that context, where you create a sound wave that's in opposite to the one that you're trying to block, and if you're doing that, the two waves cancel each other out and you get silence or near silence as a result. So the production of these two different frequencies would induce a third frequency to form within the ears of protesters, and the effect was supposedly so so intense that people couldn't withstand it. They had to get away from the sound. Altman points out that the UK has denied that such a device has ever existed, and he also mentions another source that concluded that while the British may have looked into actually making such a thing, it may never have been built. So it sounds like this is another one of those things where people said, you know, this should be able to work, but no one actually made the thing. But it does come into play when we get to audio spotlights a little later in this episode, so that's a fun little tidbit. Further, Altman writes about articles claiming that infrasound you know below the typical range of human hearing, so below that twenty Hurtz range, played at a high enough volume, like at around one hundred decibels, can disorient the listener. But Altman's research also came across scientists who said they could not confirm these findings, so whether that's actually true or not remains unknown. It's kind of funny because you know, this is an anecdote, so it's not really it's not evidence at all. But this is something that happened to me not too long ago. I was in a car with my partner and a jeep pulled up behind us, and the person in the jeep had their sound system blasting at an incredible volume, and the bass was cranked up, probably about as far as it could go, And even though we were sitting in a car with our windows rolled up, we could hear that bass pretty clearly, and it did create a rather unpleasant and disorienting sensation, though that might just be because I'm old and cranky and have nothing to do with any physiological reason. Altman specifically states that his research focused on acoustic weapons that are intended to do physical damage to a target, rather than just using sound as a way to annoy or distress someone by you know, like preventing them from getting rest, for example, which is legit. But I think we should take the use of sound as a deterrent or way of distressing someone into consideration, because while there is a lack of firm scholarship on the efficacy of sound as a weapon that causes direct physical harm or perhaps even death, we do have plenty of examples of folks using sound to make someone else's life more difficult. For example, Christmas nineteen eighty nine, five years after the song do they Know It's Christmas? Came out? Now, I think there's no denying that that particular song is torture all by itself, but it doesn't factor into the story now. In nineteen eighty nine, the US military used rock and or roll music to force Manuel Noriega to exit the Vatican embassy in Panama City, at least that was their intent. So the US won in Noriega on charges of drug trafficking and such, and Noriega had sought refuge in the embassy. So the US put some really powerful speakers on hum v's, drove the humv's around the embassy, and blasted the embassy with tunes like I thought the Law by the Clash, which is classic, or all I what is you by you too? And because the military really does have a six sense of humor Hanama by Van Halen. But mostly they played a lot of songs by guns n' Roses and the Doors. This musical assault lasted three days, but then the Pope called the President and said, hey, can y'all knock it off please? That's our embassy. And the US complied, and Noriega ultimately surrendered himself just a few days later. I don't know, maybe he missed the music. In nineteen ninety three, law enforcement agents employed the let's blast them with sound technique on David Koresh's compound in Waco, Texas. This is the infamous Branch Davidian holdout. Now. Among the sonic bombs that they dropped were various songs as well as the sound of jet planes and disturbingly, one report said, the screams of rabbits as they were being slaughtered. Yikes. Now the military has used loud music to rock the sleep and morale of prisoners of war as well, in order to soften them up for interrogation or break down their resistance by preventing them from getting enough rest, so mentally they wouldn't be able to withstand interrogation techniques. Now, I find all of this ethically troubling, to say the least, particularly in light of research that has suggested repeatedly that torture is not effective. At least, it's not effective if your goal is to get at some sort of truth, no matter how popular media might suggest otherwise. I'm looking at you, Jack Bauer, But I mean, I guess you could argue it is effective if your only goal is to make the tortured person feel miserable and powerless. Yeah, it works to that extent, but that seems you know, repugnant. You know, again, not really the same as using a weapon of war. So what about l rads l RAD That initialism stands for long range acoustic device, and in turn these actually evolved from an earlier device, the AHD or acoustic hailing device. All right, this involves a pretty tragic story. So back in two thousand, US forces aboard a Navy destroyer named the USS Coal were attacked when terrorists aboard a small boat approached the vessel and then bombed the destroyer. The attack killed more than a dozen US service members as a result. As the boat was approaching, the USS Coal attempted to hail the vessel to determine the crew's intent, but they got no response. There was no radio contact with the boat, so hailing involved using loudspeakers to send out a message over the water. But sound doesn't travel forever. As I mentioned in Monday's episode, over distance, sound waves attenuate they diminish in strength, so it was reasonable to assume that the crew on the smaller boat just couldn't hear the messages. Once the boat was close enough that those aboard the USS Coal could be sure that they were being heard, it was already too late, and the attack immediately followed. One consequence of this attack was that engineers began to develop technology designed to focus sound waves and to blast them out at high enough amplitude or volume so that intelligible sound could travel much, much further in a directed fashion. This was the acoustic hailing device, and it would allow naval forces to send an audible message, not just audible, but intelligible, as in you can understand what someone is saying, in order to warn approaching craft that they need to make their intent clear and follow orders or else potentially face defensive measures from the Navy. Essentially, the Navy would be able to say stop where you are, or we will shoot you now. To accomplish this, the device needed to be able to one blast out sound with enough energy enough amplitude to travel a far distance, and two focus that energy toward the target. And turns out you can do this with sound. So let's talk about sound beams or audio spotlights, because this is really cool. All right. So I mentioned in the previous episode that sound travels in waves, in longitudinal waves. Actually we talked about that in the active Noise Canceling episode, but these waves are pretty darn long. So I'm talking about the wavelengths of sound that are within the typical range of human hearings, so between twenty hurts to twenty killer herts. If you compare those wavelengths to like light waves sound waves in the audible range, they are enormous. And that link means that sound waves can and do bend around physical objects. They diffract. So here's a way of imagining this. Let's say you're standing on one side of a free standing opaque wall. Let's say the wall is like eight feet tall. I'm on the other side of this opaque wall. We would still be able to talk to each other, right, You could speak and I could hear you, and I could speak and you could hear me, even though there's a wall in the way and we can't see each other. Well, the light is not able to diffract around the height of the wall. The light wavelengths are so small they don't diffract around this wall. But the sound waves are long enough where they can diffract around the wall. Otherwise, if they couldn't, we would speak and the sound would just not be able to cross the wall. It would go in every other direction and we wouldn't be able to hear one another. But we know that's not the case. We know we would be able to hear each other. If light did that, by the way, it would be almost like we have X ray vision, But it doesn't work that way. That same feature, however, this long wavelength of sound makes it very hard to focus sound into a beam. Sound on its own would just travel outward from the source essentially in all directions and lose energy as it travels, or, if you prefer, the energy disperses as the sound travels outward from the source. So as you go further away from where the sound was made, it gets less audible until you get to a point where you just can't detect it at all. So how do you make sure sound is audible from very far away? Well, one way is you could just keep upping the amplitude, but that gets dangerous. Also, it would get to a point where it's so loud that everyone near the audio device would need some serious air protection, and even then there's some worry about how those vibrations would affect the human body. Keep in mind that sound through a gaseous medium is essentially changes in air pressure, and if you're blasting stuff out at like one hundred and sixty decibels, that's massive amounts of air pressure, Like it would feel like you're getting punched. Now, remember the decibel scale is also logarithmic. This is something that's hard to get your mind wrapped around unless you deal with logarithms all the time, in which case it's easy, but I think for most people it's not intuitive. So if you have a sound that's ten decibels, that means that it's ten times louder than something that's at zero decibels. Zero decibels is a sound that is barely audible. If you are talking about a sound that's at twenty decibels, twenty decibels is one hundred times louder than zero decibels. So once you get up to around one hundred and twenty decibels, you're talking about sound that's loud enough to cause permanent hearing damage or hearing loss. Once you get a little higher, you're talking about sound that's above the pain threshold. That'd be around one hundred and forty decibels or so l rads can go up to one hundred sixty decibels. That's pretty serious stuff. So it would be great if you could direct sound in a significant way, one to focus that sound, and two to prevent the sound from freaking havoc on your own side. And one way to do that is through what is called an audio spotlight, which emits sound at very very high frequencies, frequencies that are much too high for humans to be able to hear them. In fact, they're too high for dogs to hear them. Cats could probably hear them, Bats definitely could, but not so much with people. I'll explain more after we take this quick break before the break, I was talking about audio spotlights. What is an audio spotlight. It's a surface over which there are are hundreds of transducers that are capable of emitting sound. And at these frequencies, the sound wave links are much smaller than in what's in our audible range, So we're talking about things like in the say sixty five kilohertz frequency. So these transducers, they're like very tiny little speakers that are able to move super fast and super powerful, Like they don't have to be that strong because they're smaller, so you don't use as much energy to move the speaker in order to generate sound. But they are very very tiny, and because the wavelengths that they are generating are also really tiny, they aren't as affected by diffraction, So like this is something that acts more like lightwood than audible sound. So you wouldn't necessarily be able to pick up these very high frequencies if there were a wall in the way, because the sound waves are so small that they wouldn't wrap around the top of the wall and you wouldn't be able to detect them on the other side. However, it also means that the sound will travel in a much more focused way. You can direct the sound toward a target, But if you're generating sounds that are well above the range of human hearing, what good does that do? Right? Like, yeah, we can shoot a beam of sound waves using this focused approach, using very very very tiny sound waves, but if you can't perceive them directly, then what good does that do? Well? It turns out you can create actual audit sounds using these higher frequencies, because again, sound waves at high enough amplitude will interfere with one another. At low amplitude, they'll just pass through each other, but at high amplitude they will interfere. So again I talked about how noise canceling headphones creates destructive interference by creating an anti phase sound that will cancel out incoming sound. But it's also true that if you play slightly different ultrasonic frequencies, their interaction with one another can create frequencies that are actually in the audible range. I mentioned that supposed project that the Ministry of Defense of the UK did in order to dissuade protesters in Northern Ireland, and of course the Ministry of Defense said they never built that thing. But since those days we have had people build audio spotlights, and they work on essentially the same principle. You generate these different frequencies, maybe even the same frequency, just out of phase, and through that you can encode information on top of this frequency, and that information can be within the audible range. So the audio is not coming or the audible audios not coming from the speakers themselves. Right, if you were able to just isolate them playing a single frequency, you still wouldn't hear anything, even though the transducers would be generating sound, it would just be beyond our capability of sensing it. But the interaction of the sound waves themselves creates the audible sound. It's incredible. It's a really neat phenomenon. There's actually a great demonstration of this on YouTube. The channel I saw it on was NPS Physics. The videos title is audio Spotlight How a audio spotlight works. That's their grammatical error, not mine. It's actually taken from a lecture given by doctor Bruce DeNardo, and it's really entertaining. He's a great lecturer. He's very good at explaining how this works at a very high level. Does explain it's much more complicated than he's letting on. But that he's giving kind of the basic explanation of what's happening, and they do use the music of the Eagles in their demonstration. Now I happen to share the same opinion as the dude from The Big Lebowski on that particular band, except for Journey of the Sorcerer, which I think is an awesome instrumental track, and anyone who's familiar with Hitchhiker's Guide through the Galaxy is probably gonna dig it anyway. Using this method, it is possible to direct sound, and with acoustic haaling devices, the intent is to make that sound intelligible so that oncoming vessels can hear commands to stop or whatever, or to turn around. But you can also use the same capability to blast noise that is unpleasant or unsettling and that segues into the long range acoustic devices or lriads. These are not necessarily meant for haling purposes, but for stuff like crowd dispersal, and there are questions as to whether or not it is ethical to use them, or should even be legal to use them. There have been cases in which US law enforcement have used lrad's l rads for crowd control, blasting out a siren noise that's usually projecting sound between two and four killer hurts. Two killer hurts to four killer hurts. That is, that range is fairly high pitched, and it's unpleasant, especially at very high volumes. It's this piercing siren kind of sound, and if it's blasted at you loud enough, it's probably going to cause at least discomfort. And as I mentioned earlier, if the amplitude is high enough, like if you have a decibel level of around one hundred and twenty or more, and these things are capable of much more than that, then you could experience hearing loss just from relatively short exposure to these things. Of course, you could protect yourself with hearing protection, which actually works pretty darn well. That's another reason why a lot of militaries have abandoned the use of acoustic weapons, because if your enemy has ear protection, then your weapon isn't any good. It doesn't work so great. Hearing protection will reduce the decimal level enough so that it's at safe levels. It still probably won't sound great. You'll still get some of that siren noise in, but you wouldn't be in as much risk of experiencing actual hearing loss as a result of that. According to musicology now dot org, the most powerful acoustic healing devices are capable of transmitting audible sound from a distance of more than five kilometers, though most are meant for much shorter distances, like in the five hundred meter range. But don't get me wrong. Five hundred meters is still pretty darn far. I mean, that's more than five American football fields, So that's a pretty darn good distance to be able to transmit intelligible sound to a target. And as mentioned, we still don't really have a full understanding of what this effect could have on people. Jurgen Altmann research suggests that folks have made a lot of assumptions without much hard evidence to back those assumptions up. But that doesn't mean the assumptions are entirely wrong. It means that we can't be sure one way or the other without further study. And study is difficult because if the work could potentially harm your subjects, that's a huge problem. So can infra sound, you know, those very low frequency sounds below the range of human hearing. Can it at a high enough volume at enough decibels cause stuff like nausea or intestinal pain. Could it cause the dreaded brown noise, as in a sound frequency that, when played at a high enough volume, forces you to evacuate, to defecate, in other words, to poop yourself. There's no evidence of that, By the way, doesn't mean it can't happen. I just mean there's no evidence. So could it cause actual physical trauma? If you were blasting sound at like, you know, one hundred and fifty decibels, let's say it's inaudible sound. Maybe it's too low to hear. Could that very low sound at one hundred and fifty decibels cause physical harm Could it resonate with your internal organs causing them to vibrate with enough energy to hurt you. A resonance, I mean, is a thing. The classic example of resonance is you tap a crystal glass, like a champagne glass made out of crystal, and you're gonna hear it ring out a tone. Actually it rings out several tones. You get your base tone and then the harmonics of that tone, but the harmonics have less energy than your primary tone does. Anyway, if you were to play back that same base tone, that would induce the crystal champagne glass to start vibrating. It would vibrate along with this frequency you're blasting it at, if it was the resonant frequency. If it's the same frequency that generates when it when you tap it, if you blast that glass with enough volume of that tone, then it will cause the glass to deform to the point where it will shatter. So this is the class like opera singer causes glass to break using their voice trick. It's actually pretty hard to do for most singers. Usually you would need a pretty significant amount of amplification as well as incredibly good pitch to manage. It can be done, but usually it requires amplifications. It's very hard to do with your voice alone anyway. It's not just champagne flutes made of crystal that resonate. So the thought is that if you dialed an audio emitter to the right frequency, one that's low enough to penetrate the body and strong enough to really get things moving around in there, you can make a person's inerds or their air cavities inside their body vibrate. That would cause that tissue to heat up. Right. Vibration is energy, and it's like friction essentially, kind of the same way microwaves end up heating up food when you put them in the microwave, so of course that's using microwave radiation per of the electromagnetic spectrum, not acoustic waves. But I think we can all agree that having your organs all start to heat up is bad, or maybe induce air bubbles to form inside tissue that's also really bad. But as Altman points out repeatedly, there just is an evidence that this actually happens or has happened, just that there are a lot of articles that hypothesize maybe it could happen, So maybe it would, maybe it wouldn't. Finding out would require deeply unethical research and a cruel disregard for human safety or animal safety, as it turns out, and it might mean that the technology necessary to carry out such an effect would be prohibitively expensive to build and or operate if you did try to do this. So I guess that's good news. Altman's article, as I mentioned, it's free to read. I recommend going through it. It is quite long, and Alman really did his work trying to track down reputable research on the topic. The paper is longer than sixty pages, but again very easy to understand. So if you have time, check it out. That article that is really the basis for a lot of what this episode is all about, although again I went off book for the stuff that was about disrupting someone's sleep cycles or whatever. The article again, its title is Acoustic Weapons a Prospective Assessment. It's in Science and Global Security, Volume nine, two thousand and one, so check that out. Anyway, Acoustic weapons remain a thing. I still think it's really scary that we have these things that are in active use and we don't have a full understanding of the effects of that technology and how harmful they may or may not be. It may turn out that they're relatively not harmful at all, as long as your exposure to them isn't too long. But it could also turn out that they cause some pretty gnarly effects. There's the whole havana syndrome thing that I didn't get into. I'm sure the stuff they don't want you to know. Crew has done an episode on the havana syndrome. I'll have to reach out to them to make sure, but it would be weird if they hadn't. Anyway, I hope that you found this episode interesting. I hope you go check out that article. Read up on this subject, Read up on acoustic spotlights. Those things are cool. What a neat way to create this effect, Like to be able to use sound that's not in our audible spectrum to create audible sounds at a point in the distance. That's just incredible to me, Like it's phenomenal. It blows my mind. In the meantime, I hope all of you out there are doing well and I will talk to you again really soon. Tech Stuff is an iHeartRadio production. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.