Speaker 1: Get in touch with technology with tech Stuff from how
Speaker 1: stuff works dot com. Hey there, and welcome to tech Stuff.
Speaker 1: I'm your host, Jonathan Strickland. I'm an executive producer with
Speaker 1: how Stuff Works in love all things tech, and it's
Speaker 1: time for another classic episode of tech Stuff. This one
Speaker 1: published Holy cal September twenty nine, two thousand and ten. Wow,
Speaker 1: this one's really diving into the archives, and I do
Speaker 1: mean diving because this episode is all about how sonar works.
Speaker 1: Dive dive boop boop boop. So I talked a lot
Speaker 1: about echolocation in recent episodes, this is the episode where
Speaker 1: we really looked at the tech behind sonar. So listen
Speaker 1: as Chris and I explore the incredible world of sonar.
Speaker 1: I hope you enjoy. Have I got this straight? Jonesy,
Speaker 1: A forty million dollar computer tells you you're chasing an earthquake,
Speaker 1: but you don't believe, and you come up with this
Speaker 1: on your own that had a direct bearing to our
Speaker 1: topic today, and that topic would be sonar, sound navigation
Speaker 1: and ranging. Well, that pretty much covers it, so well,
Speaker 1: that's exactly what it is. It's one of those nice,
Speaker 1: nice words that sort of covers it. So yeah, no,
Speaker 1: it's it's it's very it's very much exactly what sounds like.
Speaker 1: It's using sound to navigate and to to find the
Speaker 1: distance from other objects. As it turns out, there a
Speaker 1: lot of ways to use sonar um and we'll get
Speaker 1: into that in a minute, but there are also a
Speaker 1: lot of different types of applications, uh, different ways to
Speaker 1: use it as in like um, different kinds of equipment
Speaker 1: that that can be used to find depth and identify
Speaker 1: things in the water and even map the cea floor
Speaker 1: if you want to do that. Ye, and uh, actually
Speaker 1: the you know, we're not the only ones to to
Speaker 1: use sonar, not by a long shot. True. Dolphins and
Speaker 1: whales use it to other animals. Yes, that would be
Speaker 1: an echolocation, Yes, yeah, exactly, that's what the sonars based
Speaker 1: off of. It's the idea of the way sound travels.
Speaker 1: And so if you sound travels and waves, it's a
Speaker 1: it's actually a physical uh thing. It's you know, we
Speaker 1: don't see it, but it is a physical effect. When
Speaker 1: you make a sound, you are causing stuff to bang
Speaker 1: against each other. That sounds so so scientific. It's though,
Speaker 1: so when sound travels, it's really lots of air molecules
Speaker 1: bouncing against each other until well really just until it disperses,
Speaker 1: so it keeps on going. I mean, and we detect sound,
Speaker 1: of course through hearing, but there are other ways to
Speaker 1: detect it. There there are sounds that are outside of
Speaker 1: our range of hearing that we can sense. Like there's
Speaker 1: some that are so low that you know, you can't
Speaker 1: hear it, but you can feel it. That's scrumbing feeling
Speaker 1: from from from and when sound hits a really solid object,
Speaker 1: it bounces it, it refracts off as some of it
Speaker 1: reflects back and uh, and that's where we get the
Speaker 1: whole echo effect. So when you're in the right kind
Speaker 1: of environment and you speak and you hear that echo,
Speaker 1: that's those sound waves bouncing back and coming back to you. Well,
Speaker 1: you can use this to find your way around an environment, right, Well, um,
Speaker 1: so where does sonar come from? Then we have to
Speaker 1: figure out exactly. Uh, really when that all started taking place,
Speaker 1: and I think it was really probably, I mean, people
Speaker 1: have been doing it for a long time. Yeah, you could,
Speaker 1: you could identify things and under the surface of the water.
Speaker 1: But why are you creating him? Because my favorite man
Speaker 1: of all time did some experiments with listening to sound
Speaker 1: through water. Okay, Leonardo da Vinci, we just finished talking
Speaker 1: about him a second ago, which I'll try and make
Speaker 1: sure that the podcast publish in the right order. But no,
Speaker 1: Leonardo da Vinci back in experimented with with listening to
Speaker 1: sounds through water. He would insert a tube into into
Speaker 1: water and put his ear to the tube like straw. Yeah,
Speaker 1: pretty much like a straw. Larger than a straw, Mr
Speaker 1: da Vinci. Why are you listening to your drink if
Speaker 1: you had a drinking problem? So, but yeah, he would
Speaker 1: use this to to kind of listen to uh to
Speaker 1: the two noises, with the idea that if you could
Speaker 1: create the right system, you would be able to detect
Speaker 1: when things were approaching through the water. Now, during da
Speaker 1: Vinci's time, this wasn't really that big a problem. Things
Speaker 1: usually approached on the water, and if they were in
Speaker 1: the water, they weren't really something you needed to worry about.
Speaker 1: The frogman of his day not not so effective, but
Speaker 1: getting all the way up to the eighteen or the
Speaker 1: nineteenth century, rather they hundreds uh you started to some
Speaker 1: some lighthouses would have underwater bells that would be uh
Speaker 1: placed around the area to warn ships of of hazards,
Speaker 1: so ships could actually listen as they approached land and
Speaker 1: they heard bells, they knew they were coming up on
Speaker 1: shoals and they could they could alter their course before
Speaker 1: running aground. And then uh in around nineteen sixteen. Uh
Speaker 1: it was an early passive so in our system. Will
Speaker 1: explain what that means UH in a minute. But they
Speaker 1: were using strings of microphones towed by ships, which is
Speaker 1: again something that dates up to the present in a
Speaker 1: different form. But by um and of course thinking back
Speaker 1: on it, that's you know World War one, right, the
Speaker 1: British and American scientists had developed an active so in
Speaker 1: our system, UM, you know that that was a big
Speaker 1: concern at the time because of course the German uh
Speaker 1: U boats were patrolling and it was some scary stuff. Yeah,
Speaker 1: actually it was. It was a very intimidating weapon, definitely.
Speaker 1: I mean there had been something sorry I keep coming,
Speaker 1: there had been submarines before that, but sure, the German
Speaker 1: U boats in World War One were a very effective
Speaker 1: way of taking control of the Atlantic Ocean and the
Speaker 1: shipping back and forth between the continents. So it's sonar
Speaker 1: was something that they were very rapidly trying to work
Speaker 1: out exactly. And it's funny because well, not funny, but
Speaker 1: it's it's interesting to me that really the the event
Speaker 1: that kind of started all this off wasn't World War One,
Speaker 1: because by then they were pretty far into it, but
Speaker 1: they did have an interest, yes, yes, to talk about
Speaker 1: To talk about how this really started off, you really
Speaker 1: got to look back to a certain event that happened
Speaker 1: in nineteen twelve. Oh really, and what was that event? Well,
Speaker 1: there was a little boat that happened to sink. Oh yes,
Speaker 1: that little boat. Yeah, yeah, don't they go um, my
Speaker 1: heart will go onto Yeah, the Titanic disaster, Titang disaster.
Speaker 1: Following that, that's when we saw the first patent for
Speaker 1: underwater echo ranging demands. So that was that was where
Speaker 1: the first patent was filed UM and it was filed
Speaker 1: at the British Patent Office by Lewis Richardson, who was
Speaker 1: a meteorologist UM and he he had come up with
Speaker 1: this idea of creating a way to locate objects underwater
Speaker 1: using sound. You would you would fire sound out, you
Speaker 1: would measure the sound that comes back, and through that
Speaker 1: you would figure out what was there, how far away
Speaker 1: it was, whether it was moving or not. I mean,
Speaker 1: these were all the concepts now back in nineteen twelve,
Speaker 1: they didn't really have a way of achieving this. He
Speaker 1: he panted the idea, but it wasn't until, like Chris said,
Speaker 1: around nineteen eighteen that we started to really see accelerated development,
Speaker 1: because then you had a wartime use for it, and
Speaker 1: it was really important to find a way to to
Speaker 1: detect those submarines, those U boats. Yeah, icebergs were were
Speaker 1: obviously concerned, especially in the North Sea and various like that.
Speaker 1: Um because you know, as as is in the case
Speaker 1: of many cliches, there is an element of truth in it.
Speaker 1: The tip of the iceberg really is, you know, the
Speaker 1: smallest right part, and so much of it is underwater,
Speaker 1: and you can't tell without some kind of device. And
Speaker 1: I think that's uh. The earliest, earliest sonar or the
Speaker 1: earliest echolocation devices were not very precise. In fact, they
Speaker 1: were so imprecise that they could tell you that there
Speaker 1: was an iceberg, but could not tell you where the
Speaker 1: iceberg was, So you you might know that there's an
Speaker 1: iceberg somewhere within a two mile radius of your ship,
Speaker 1: which is not entirely helpful, although I guess It tells
Speaker 1: you to keep an eye out so that you you
Speaker 1: don't see it just before you hit it, you know,
Speaker 1: you you know, to keep an eye out for for
Speaker 1: icebergs um. By the by the time World War two
Speaker 1: came around, that's when the because early sonar was really
Speaker 1: led by the British, they made the biggest advances in
Speaker 1: sonar technology. They didn't call it sonar. They called it
Speaker 1: as dick A S D I c UH and UH.
Speaker 1: The A S D was actually a code. It was
Speaker 1: It was so that the people outside of the top
Speaker 1: secret development wouldn't know what the scientists were working on.
Speaker 1: So people say, well, what does as DICK stand for? Well,
Speaker 1: it kind of stands for keep your nose out of
Speaker 1: it MR. So it wasn't really until World War two
Speaker 1: that the United States actually outpaced the British in this
Speaker 1: technology and uh, and that's when, you know, the term
Speaker 1: sonar started to pop up, and that eventually became the
Speaker 1: de facto term for the technology. Right right now, we
Speaker 1: should probably at this point go into the two basic,
Speaker 1: very very very basic types of sonar, so active and passive.
Speaker 1: Active and passive, and I think passive is the easiest
Speaker 1: one to explain yes, Basically you're receiving the sounds of
Speaker 1: the water around you. You're listening, yes, so simply listening.
Speaker 1: So passive passive sonar is where you have some sort
Speaker 1: of sound collection device, usually a hydrophone, which is just
Speaker 1: a microphone that you can use in the water. Right,
Speaker 1: you would have hydrophones play and you may have a
Speaker 1: couple of different passive sonar stations so that you have
Speaker 1: hydrogen phones directed in specific areas, so that way you
Speaker 1: can tell where the sound is coming from, not just
Speaker 1: that there is sound, and you listen carefully for any
Speaker 1: kind of indication of other activity in the water. And
Speaker 1: it's interesting because as I was doing my research, I
Speaker 1: discovered that that if you were a trained sonar operator, yes,
Speaker 1: and you heard a submarine. Let's say you're in a
Speaker 1: submarine and you heard another submarine, right, you could actually
Speaker 1: identify where that submarine what was from, based upon the
Speaker 1: sound you heard. Yes, that is correct, it is That
Speaker 1: is to me as phenomenal. Well, every uh, as I
Speaker 1: understand it, every ship of any kind, submarine or ship
Speaker 1: or you know, I guess boat depending on what's on
Speaker 1: the boat, has its own audio signature. Could be the engines,
Speaker 1: um or basically anything that's going on if they are
Speaker 1: electronics on board did make a noise if you know,
Speaker 1: fans things like that. Some those things can help identify, um,
Speaker 1: another vessel in the water to the listening vessel. Yeah.
Speaker 1: For example, in the United States, most of the submarines
Speaker 1: were operating on a sixty hurts alternating current power system,
Speaker 1: but in Europe they were operating on fifty hurts power systems.
Speaker 1: So just the the frequency of the sound would be
Speaker 1: enough to indicate to you whether you were listening to
Speaker 1: a US ship or a European ship. And uh, you
Speaker 1: couldn't necessarily if everything was running the way it should,
Speaker 1: you might not hear anything at all, or you might
Speaker 1: hear very little. Um. It was if you didn't sound
Speaker 1: proof all of your equipment, like if if the various
Speaker 1: elements weren't uh weren't insulated properly, then stuff would rattle
Speaker 1: and you could you could actually hear the rattling. In fact,
Speaker 1: one source I read said that, uh, you know, the
Speaker 1: location of a submarine might be given away by someone
Speaker 1: accidentally dropping a wrench onto the floor the deck. I guess, um,
Speaker 1: I assume they're decks and submarines I've never been a
Speaker 1: board one. Yes, I believe there are so. Yes, if
Speaker 1: you were to drop a wrench to the deck, it
Speaker 1: could create a sound that someone another sonar operator might
Speaker 1: be able to pick up and say, all right, they're
Speaker 1: they're support um. So it's it's a pretty interesting thing.
Speaker 1: And the passive sonar, by the way, was more important
Speaker 1: for submarines because if they use the active method, they
Speaker 1: would actively be giving away their location. Yes, that's because
Speaker 1: active active sonar systems are giving off a pulse of sound. Yeah,
Speaker 1: often called a ping. Yes, so you ping the sound
Speaker 1: out and uh, and then they wait for the sound
Speaker 1: waves to come back and based upon how long it
Speaker 1: takes and how much how strong the signal is, that's
Speaker 1: how you kind of determine what it is, your your hearing.
Speaker 1: You know how far away the object is, and you
Speaker 1: know what it might be. You know how many how
Speaker 1: many submarine movies have you seen where they do that
Speaker 1: tense moment where nobody's moving a muscle, they don't wait wait,
Speaker 1: you know, and there's just like you know, you watch
Speaker 1: the beads of sweat rolled down the submariner's faces. Yes,
Speaker 1: there's the there's the one that I quoted at the
Speaker 1: beginning of this podcast. Um, yeah, no, no, but there
Speaker 1: are many you know that that then that's the thing
Speaker 1: is you have to be very very quiet and that
Speaker 1: kind of a situation because any little thing can be
Speaker 1: picked up by the ping. And here's what's really interesting
Speaker 1: to me is that the ping is well really anything
Speaker 1: could be picked up by passive sonar. I know, I
Speaker 1: just want to make an Okay, I got you. I
Speaker 1: was about for the rhyme. I sorry, so active, but
Speaker 1: with the rhyme of an ancient you stopped at one
Speaker 1: of three. Chris and I will be back in just
Speaker 1: a moment to continue our discussion about sonar, but first
Speaker 1: let's take a quick break to thank ours. Answer the
Speaker 1: active sonar. The basis of that really rests in the
Speaker 1: fact that we know how fast sound travels through water.
Speaker 1: But we we do, but it's really complicated. You would think, oh,
Speaker 1: it's got to be some constant right, not exactly actually
Speaker 1: constantly constant. Yeah, The speed of sound traveling through water
Speaker 1: depends on several things. Depends on the temperature of the water,
Speaker 1: the salinity of the water, and the depth of the water,
Speaker 1: and all of these things affect the density of the water,
Speaker 1: which makes sense. Right. If you've got more molecules packed together,
Speaker 1: sounds going to travel faster through that because the molecules
Speaker 1: hit each other more quickly, Like it doesn't take much
Speaker 1: for a molecule they'll run into another molecule. The sound
Speaker 1: travels much much further and much faster, um if you've
Speaker 1: got them spread out the and they lose some of
Speaker 1: their energy as they are moving, and so it doesn't
Speaker 1: travels far and it doesn't travels quickly. So the rule
Speaker 1: of thumb is that it's four thousand three eight eight
Speaker 1: feet per second. And then you have to add all
Speaker 1: these modifiers in right right now, there are some some
Speaker 1: things that you can do. Uh. There is a system
Speaker 1: that I read about, the A N B q H
Speaker 1: DASH one speed of Sound measuring system, which is you know,
Speaker 1: a modern sonar system, um. But it evaluates the depth
Speaker 1: and temperature and salinity of the water to get an
Speaker 1: idea of how the speed of sound is going to
Speaker 1: travel through that particular water at the time. Obviously, that's
Speaker 1: probably a very expensive piece of equipment because it's doing
Speaker 1: those calculations for you. But that's what modern computing technology
Speaker 1: gets you. Um. But yeah, it gives you uh, you know,
Speaker 1: sonar technicians can use that equipment to get an idea
Speaker 1: of what's going on with a lot better accuracy, and
Speaker 1: it also helps them avoid being detected by other sonar
Speaker 1: equipment because they have an idea of you know, what's
Speaker 1: the current conditions are underwater where they are, right, So,
Speaker 1: if you're using active sonar, you might be using it
Speaker 1: for well if in wartime you would have ships and
Speaker 1: and even aircraft using active sonar to try and detect
Speaker 1: submarines and then drop depth charges down to to disrupt
Speaker 1: the submarines. Ah yes, uh so active sonar in wartime
Speaker 1: is often used by by vessels that can move fast
Speaker 1: enough so that it's not it's not a big deal
Speaker 1: about giving away your location like destroyers for example. Exactly exactly.
Speaker 1: If you're a submarine, you don't tend to use active
Speaker 1: sonar as often. Um yeah, especially when you're submerged in
Speaker 1: trying to avoid detection, because that's you can't move nearly
Speaker 1: as quickly as the enemy destroyers are coming after you. Right. So,
Speaker 1: so if you're also you could be using active sonar,
Speaker 1: not just in wartime, but also if you're mapping the
Speaker 1: ocean floor then you want you want to be as
Speaker 1: accurate as possible, which means you have to have you know,
Speaker 1: you have to factor in all those elements we were
Speaker 1: talking about before, the salinity and temperature and depth and
Speaker 1: all that. UM. If you if you're just using sonar
Speaker 1: as a fish finder, because there are plenty of of
Speaker 1: products on the market that do that, you don't have
Speaker 1: to worry quite that level of accuracy because you're not
Speaker 1: you're usually not talking about the same kind of distances
Speaker 1: involved that we're talking about, and usually the you know,
Speaker 1: the depth is not as big a factor. So really
Speaker 1: in that case, uh, you know, you could use a
Speaker 1: constant speed for the sound through water and not be
Speaker 1: so inaccurate. There. You're looking for schools of fish. They're
Speaker 1: going to be moving around anyway, so it's not like
Speaker 1: it's um, it's not like like the kind of precision
Speaker 1: work you need to do with these other elements. Right.
Speaker 1: Actually that that's one of the things that I found
Speaker 1: fascinating during part of the the sentar technicians training. They actually,
Speaker 1: uh are known to record things that are just natural sound,
Speaker 1: like the sounds of fish, um tectonic plates. I'm not
Speaker 1: I'm not sure what kinds of sounds does give off
Speaker 1: really low groaning ones, yes, kind of like my back.
Speaker 1: But that's but that's the the trick is you once
Speaker 1: they understand what those things are, they can eliminate them.
Speaker 1: They go, oh, well, that's just a large school of fish,
Speaker 1: you know. Oh that's you know, an alien spaceship that's
Speaker 1: crashed underwater, that kind of stuff. Um, I make a joke,
Speaker 1: but no, that that that Uh. I was wondering about
Speaker 1: that when I was reading about civilian uses for so
Speaker 1: in our technology, and I was thinking, wow, how do
Speaker 1: they know, you know, what is a school of fish?
Speaker 1: And obviously if you're on a lake and it's it's
Speaker 1: probably going to be the stuff that's moving around underwater.
Speaker 1: It's not likely to be an enemy submarine. But you know,
Speaker 1: detecting a fish versus you know, a snake or some
Speaker 1: other type of monster, we've gotten very silly, very quickly.
Speaker 1: Well no, I mean people have been used saying that
Speaker 1: kind of equipment to try and determine whether or not
Speaker 1: there are yeah, so our equipment. Yes, there are plenty
Speaker 1: of monster hunters who have tried to use like a
Speaker 1: fish finder, yeah essentially. But that's the thing is that there.
Speaker 1: There are schools of fish in Locknest and schools of
Speaker 1: eels as well, So you get a school of fish
Speaker 1: or a school of eels that's going to give you
Speaker 1: a reading. And then people say, hey, look there's a
Speaker 1: monster down there. Not necessarily and I have to say,
Speaker 1: you know, I've mentioned before in the podcast that I'm
Speaker 1: a skeptic. Out of all the things to be skeptical about,
Speaker 1: the lock best monster was the one I held onto
Speaker 1: the longest because I want to believe it's real. I
Speaker 1: don't believe it's real, but I want to so badly.
Speaker 1: UM and a cottage on the shore. There's a shadow
Speaker 1: on the door. No different kinds of sonar okay, side
Speaker 1: scan center UM. This is a device used to find
Speaker 1: objects on the sea floor and figure out what they are.
Speaker 1: They usually have a tow fish or a tow body,
Speaker 1: which is a UM basically sophisticated device that goes in
Speaker 1: the water and is towed behind the ship, and a
Speaker 1: device that processes the signals on the top UM. What
Speaker 1: happens is they use the the sound energy which is
Speaker 1: transmitted in a fan shaped pattern and goes about a
Speaker 1: hundred meters down or so. Basically, they used the information
Speaker 1: that comes back to create an image of what's on
Speaker 1: the sea floor. So if they get a really strong
Speaker 1: signal um back, that appears as a light image on
Speaker 1: the screen, whereas weaker signal would show darker images. So
Speaker 1: you get uh, sort of a black and white image.
Speaker 1: I don't know if it's actually black and white, because
Speaker 1: I was reading copy and it might be photo bright
Speaker 1: green and dull, right right, But you can get an
Speaker 1: idea of what the the bottom of the area you're
Speaker 1: looking at. I guess it could be a lake or
Speaker 1: the ocean. Um they don't they don't offer the same
Speaker 1: kind of depth information as the military would use to say, oh,
Speaker 1: well we you know, we're about to run around. It's
Speaker 1: not the same kind of application of sonar. Also, we
Speaker 1: should add that at certain depths, once you get really
Speaker 1: really deep, the water gets so dense that it can
Speaker 1: refract sound waves. So you you start to lose the
Speaker 1: ability to really map the ocean floor with sound because
Speaker 1: the water itself is so dense that it's it's it's
Speaker 1: mucking things up. Also, I guess I should go ahead
Speaker 1: and mention as well. We've talked a lot about the sonar.
Speaker 1: The sonar really has three main elements to it. Yes,
Speaker 1: there's a transmitter which transmits the sound right right, we
Speaker 1: didn't really talk about it, but there's a transmitter that's
Speaker 1: that's what passes on the signal. UH. It's an electric
Speaker 1: signal that goes to a transducer. Now, transducers, what they
Speaker 1: do is they convert one kind of energy into another
Speaker 1: kind of energy. In the case of sonar, it's converting
Speaker 1: sound electricity rather into sound, right active for this is
Speaker 1: for active sonar clearly. And then you've got to receive
Speaker 1: or that receives the signals when they come back, um
Speaker 1: and and then you usually have a display. So there's
Speaker 1: a transmitter, transducer, and receiver. This is for again active sonar.
Speaker 1: With the passive sonar, you just need receivers really microphones, hydrophones,
Speaker 1: um and and there are plenty of stationary UH sonar
Speaker 1: UH stations, and I guess stationary stations, thank you, Jonathan,
Speaker 1: you're both repetitive and redundant. But at any rate, there
Speaker 1: are plenty of these in the ocean. The lots of
Speaker 1: different militaries have them station stationed at different spots along
Speaker 1: the coast to detect things like possible incoming submarines, that
Speaker 1: kind of thing. We have a bit more to say
Speaker 1: about sonar technology, but before we get to that, let's
Speaker 1: take another quick break to thank our sponsor. There was
Speaker 1: a sound detective in n It was actually detected several
Speaker 1: times over the summer of U in the Pacific Ocean
Speaker 1: by by a hydrophone array, and the sound was a
Speaker 1: very low frequency sound generated over a pretty extended uh
Speaker 1: time frame several I think it's several minutes long, and
Speaker 1: it's called the bloop. The bloop is um this odd
Speaker 1: sound that that we're not really sure what made this noise.
Speaker 1: If it was organic, then it would have to be
Speaker 1: a creature larger than any that we've previously identified. So
Speaker 1: if it were a whale, it would have to be
Speaker 1: such an enormous whale that we've never seen it. Uh Ever, Yeah,
Speaker 1: so it would be be ginormous, right to use the
Speaker 1: technical term. It's more likely that the bloop is ah
Speaker 1: was some sort of geological byproduct, right, But at any rate,
Speaker 1: this sound was located or the location of the sound
Speaker 1: is probably somewhere around fifty degrees south hundred degrees west.
Speaker 1: What's interesting to lovecraft Ian fans is that that's not
Speaker 1: that far off from the supposed coordinates of Reallyer, which
Speaker 1: is Cathulu's city of the Deep. So some people have jokingly,
Speaker 1: tongue in cheek, said that this noise was dead Cathulu
Speaker 1: snoring because in his house, and really dead Cathul lies dreaming.
Speaker 1: Alright then, and also, let's some we can actually play
Speaker 1: the sounds. So what we're gonna do here is we're
Speaker 1: gonna just take a second. We're gonna play the sound.
Speaker 1: This is a sound that's off of the U. S.
Speaker 1: Government's websites, and it is specifically the sound sped up
Speaker 1: sixteen times. Now, I don't know about you. I think
Speaker 1: that was I was pretty certain it was a bunch
Speaker 1: of people flushing all at the same time. Could have
Speaker 1: also been that it might have been during the Super Bowl. Wait,
Speaker 1: it was the summer of ninety seven, so it couldn't
Speaker 1: have been. I don't know anything about sports, but even
Speaker 1: I know it doesn't happen in the summer. It was
Speaker 1: world it was the World Cup, except that wouldn't have been.
Speaker 1: It wouldn't have been a World Cup. Okay, so our
Speaker 1: speculation goes awry. Also, we had someone on Facebook, I think,
Speaker 1: asked us about the blue. Yes, there that goes and
Speaker 1: that goes out to you random Facebook person. All right,
Speaker 1: um so, uh, you know, I did look up some
Speaker 1: other interesting related technology like lidar, which is a light
Speaker 1: detected light detection and ranging system. Doesn't use sound, he
Speaker 1: uses light, but it is used mathemetric lighter is used
Speaker 1: to determine the depth of water. UM. It uses lasers,
Speaker 1: pulses of lasers sent out at two frequencies. UM. There's
Speaker 1: an infrared pulse which is a lower frequency and it
Speaker 1: reflects the surface, so you know where the surface of
Speaker 1: the water is. And then it uses green lasers that
Speaker 1: have a higher frequency that reflects off the bottom of
Speaker 1: the area. Interesting, and it works pretty similar to echolocation
Speaker 1: because it's getting reading for the top and the bottom
Speaker 1: of the depth, so you get an idea of how
Speaker 1: deep the water is. And they use this um from
Speaker 1: aerially generally, well from their mounted on aircraft. Um so
Speaker 1: according to Noah, and I mean the National Oceanic and
Speaker 1: Atmospheric Administration, not the guy with the big boat. That's
Speaker 1: the second time you've made that joke on this pod,
Speaker 1: not this particular episode, but in the series. Yeah, well
Speaker 1: you know, but yeah, and depending on how clear the
Speaker 1: water is, they can determine depths up to fifty and
Speaker 1: this is really useful for those, uh, really hazardous areas
Speaker 1: where it's might be difficult to get a reading from
Speaker 1: a vessel water borne vessel. It would be dangerous put
Speaker 1: a ship there exactly reefs and shoal and that sort
Speaker 1: of thing, which is exactly why you'd want to know
Speaker 1: what it's like, you know, underneath the surface of the water,
Speaker 1: so you can get an idea for navigation purpose. I
Speaker 1: mean really sonar Just don't mean to interrupt, but the
Speaker 1: reason why sonar it was so important early on is
Speaker 1: because light does not travel through water very well, like
Speaker 1: just normal light. And you know, you go down just
Speaker 1: a couple hundred feet and it's it gets dark really fast.
Speaker 1: And anybody who's swam in the Atlantic Ocean knows that
Speaker 1: it's not exactly the clearest water. Uh so it will
Speaker 1: be especially difficult to see in in you know, water
Speaker 1: with a lot of salinity and trabidity. And of course
Speaker 1: if you get it at pretty intense depths, then you
Speaker 1: don't want to have any windows in your device at
Speaker 1: all because the pressure is too great. Um. Before we
Speaker 1: get to the next segment. Sure, I was going to
Speaker 1: mention too that you can you can actually use sonar
Speaker 1: from uh, you know, from the air as well. If
Speaker 1: you're using a sona boy, which is basically a buoy
Speaker 1: that is equipped with sowner equipment that is lowered I
Speaker 1: guess by helicopter would probably be the best. Uh. That's
Speaker 1: where I've actually seen it down where they lower it
Speaker 1: into you know, so there's floating on the surface of
Speaker 1: the water that they can get readings UM from anything
Speaker 1: that might be in the area. Yeah, that's pretty cool.
Speaker 1: That's often used in wartime as well, because it's a
Speaker 1: way for you know, you send a helicopter out to
Speaker 1: the general region where you believe there's a submarine. You
Speaker 1: use these to try and locate the submarine. Then you
Speaker 1: use the depth charges, which are really just explosives that
Speaker 1: that sink into the water before exploding UM and then
Speaker 1: try to damage or or disrupt the submarine in some
Speaker 1: way whereas the submarine is trying desperately to or the
Speaker 1: people in the submarine anyway, or trying desperately to avoid detection,
Speaker 1: or you know, sometimes they'll use things like UM decoy
Speaker 1: explosions so you create enough noise in the water, and
Speaker 1: it becomes very difficult to pinpoint a specific object. Um
Speaker 1: And I know you wanted to discuss that it's not
Speaker 1: all that sonar is not all necessarily beneficial, that it
Speaker 1: can actually have a negative impact on the environment. Right,
Speaker 1: we're actually the creatures living in the environment. We mentioned
Speaker 1: that that whales and dolphins use echolocation in order to
Speaker 1: navigate their environments. Um. Sometimes there have been reports that
Speaker 1: that the low frequencies used in sonar equipment have disrupted
Speaker 1: that they're this marine life. That in some cases there
Speaker 1: may be instances where it has spooped a pot of
Speaker 1: whales for example, and and and so there there's some
Speaker 1: studies that suggest that some whales are suffering from a
Speaker 1: kind of um uh well, sort of a pressurization sickness
Speaker 1: because they're surfacing so quickly that they are uh it's
Speaker 1: kind of like whales getting the bends. Yeah, actually it's
Speaker 1: exactly like welles getting the bens. Because the report I
Speaker 1: saw was actually from a uh UK organization called Marine Connection,
Speaker 1: which is a pro um water life organization, and they
Speaker 1: had cited to study from the magazine Nature from two
Speaker 1: thousand three, which was citing an instance in which ten
Speaker 1: beaked whales UH surface too quickly off the Canary Islands
Speaker 1: UM in two thousand two and they got the bends.
Speaker 1: The whales got the bends. And apparently the situation is
Speaker 1: especially prominent for deep diving animals such as a beaked whale,
Speaker 1: and it may be related to the terrain underneath the water.
Speaker 1: If it's really steep um sharp drop off, that may
Speaker 1: affect the way that the sound waves are traveling underwater
Speaker 1: and maybe especially confusing um no. UH also mentioned that
Speaker 1: there might be problems for deep diving species, but said
Speaker 1: that more study needs to be done on on these
Speaker 1: kinds of strandings to find out if it's limited to
Speaker 1: the surroundings, if it actually is the c floor that
Speaker 1: is playing into it, or whether it is strictly the
Speaker 1: sonar itself. You know, before they can make a decision
Speaker 1: as to what's going on. But the Marine Connection has
Speaker 1: asked the UH. UM they've actually gotten involved and suggested
Speaker 1: to the European Parliament and it asked for a ban
Speaker 1: on high intensity sonar in certain areas. UM. So you know,
Speaker 1: there there are concerns that it may cause UH some
Speaker 1: some harm. Basically that they can swim into uh, dangerous
Speaker 1: terrain to it. That is also an issue. If they're
Speaker 1: they're momentarily confused, but in dangerous waters, that could be
Speaker 1: long enough for there to be a serious problem. Right,
Speaker 1: So yeah, there there are some concerns about this technology,
Speaker 1: which you know, we've been using for almost a century
Speaker 1: now regularly. Yeah, and we're still some of them, like
Speaker 1: the passive systems. Of course, that's not a problem because
Speaker 1: the passive systems, all they're doing is listening. They're not
Speaker 1: sending out any signals. So not all sonar is bad
Speaker 1: sonar even from a marine life standpoint. Oh no, it's
Speaker 1: still an incredibly useful technology, right, you just have to
Speaker 1: learn how to use it responsibly so that you're not
Speaker 1: causing harm to the environment or to marine life in particular. Well,
Speaker 1: that wraps up this classic episode of tech Stuff how
Speaker 1: sonar works. It was fun to go back and revisit
Speaker 1: that and listen to a version of Jonathan that's eight
Speaker 1: years younger than I am today. Holy cal Uh. I
Speaker 1: look forward to bringing you more of these classic episodes
Speaker 1: in the future. If you have any suggestions of topics
Speaker 1: that should cover in current episodes of tech Stuff, because
Speaker 1: new splash. I cannot travel back in time and record
Speaker 1: a new classic episode that that the way Back Machine
Speaker 1: will not let me do that. It's apparently some sort
Speaker 1: of I don't know. They call it a Grandma paradox.
Speaker 1: I don't understand. But if you have a suggestion for
Speaker 1: a future episode, let me know. Send me an email.
Speaker 1: The addresses tech stuff at how stuff works dot com.
Speaker 1: Trought me a line on Twitter or Facebook to handle
Speaker 1: for both of those is text stuff H s W.
Speaker 1: Don't forget to go to t public dot com slash
Speaker 1: tech stuff and check out our merchandise store. Maybe there's
Speaker 1: something there that you would love to have as a
Speaker 1: gift for yourself or a loved one, So go check
Speaker 1: that out. T E public dot com slash tech stuff,
Speaker 1: and don't forget to follow us on Instagram and I'll
Speaker 1: talk to you again really soon. For more on this
Speaker 1: and thousands of other topics. Is that how stuff works
Speaker 1: dot com.