WEBVTT - TechStuff Classic: How Sonar Works 0:00:04.120 --> 0:00:07.160 Get in touch with technology with tech Stuff from how 0:00:07.200 --> 0:00:13.680 stuff works dot com. Hey there, and welcome to tech Stuff. 0:00:13.720 --> 0:00:16.599 I'm your host, Jonathan Strickland. I'm an executive producer with 0:00:16.640 --> 0:00:19.040 how Stuff Works in love all things tech, and it's 0:00:19.079 --> 0:00:23.439 time for another classic episode of tech Stuff. This one 0:00:23.960 --> 0:00:30.880 published Holy cal September twenty nine, two thousand and ten. Wow, 0:00:30.920 --> 0:00:33.440 this one's really diving into the archives, and I do 0:00:33.520 --> 0:00:37.400 mean diving because this episode is all about how sonar works. 0:00:38.159 --> 0:00:42.440 Dive dive boop boop boop. So I talked a lot 0:00:42.440 --> 0:00:46.320 about echolocation in recent episodes, this is the episode where 0:00:46.400 --> 0:00:50.320 we really looked at the tech behind sonar. So listen 0:00:50.440 --> 0:00:55.640 as Chris and I explore the incredible world of sonar. 0:00:55.680 --> 0:00:58.400 I hope you enjoy. Have I got this straight? Jonesy, 0:00:58.720 --> 0:01:01.840 A forty million dollar computer tells you you're chasing an earthquake, 0:01:01.880 --> 0:01:04.120 but you don't believe, and you come up with this 0:01:04.280 --> 0:01:09.320 on your own that had a direct bearing to our 0:01:09.360 --> 0:01:14.399 topic today, and that topic would be sonar, sound navigation 0:01:14.600 --> 0:01:19.680 and ranging. Well, that pretty much covers it, so well, 0:01:19.760 --> 0:01:21.560 that's exactly what it is. It's one of those nice, 0:01:22.640 --> 0:01:24.679 nice words that sort of covers it. So yeah, no, 0:01:24.720 --> 0:01:27.600 it's it's it's very it's very much exactly what sounds like. 0:01:27.640 --> 0:01:32.080 It's using sound to navigate and to to find the 0:01:32.200 --> 0:01:35.120 distance from other objects. As it turns out, there a 0:01:35.160 --> 0:01:37.959 lot of ways to use sonar um and we'll get 0:01:38.000 --> 0:01:40.320 into that in a minute, but there are also a 0:01:40.360 --> 0:01:44.360 lot of different types of applications, uh, different ways to 0:01:44.640 --> 0:01:48.360 use it as in like um, different kinds of equipment 0:01:48.640 --> 0:01:52.080 that that can be used to find depth and identify 0:01:52.160 --> 0:01:55.360 things in the water and even map the cea floor 0:01:55.400 --> 0:01:57.520 if you want to do that. Ye, and uh, actually 0:01:57.600 --> 0:01:59.800 the you know, we're not the only ones to to 0:02:00.120 --> 0:02:03.080 use sonar, not by a long shot. True. Dolphins and 0:02:03.080 --> 0:02:05.880 whales use it to other animals. Yes, that would be 0:02:05.880 --> 0:02:09.920 an echolocation, Yes, yeah, exactly, that's what the sonars based 0:02:09.919 --> 0:02:12.799 off of. It's the idea of the way sound travels. 0:02:12.919 --> 0:02:15.200 And so if you sound travels and waves, it's a 0:02:15.280 --> 0:02:18.680 it's actually a physical uh thing. It's you know, we 0:02:18.720 --> 0:02:21.840 don't see it, but it is a physical effect. When 0:02:22.040 --> 0:02:26.000 you make a sound, you are causing stuff to bang 0:02:26.080 --> 0:02:31.359 against each other. That sounds so so scientific. It's though, 0:02:32.040 --> 0:02:35.160 so when sound travels, it's really lots of air molecules 0:02:35.160 --> 0:02:39.400 bouncing against each other until well really just until it disperses, 0:02:39.680 --> 0:02:42.960 so it keeps on going. I mean, and we detect sound, 0:02:42.960 --> 0:02:45.800 of course through hearing, but there are other ways to 0:02:45.960 --> 0:02:48.480 detect it. There there are sounds that are outside of 0:02:48.600 --> 0:02:52.000 our range of hearing that we can sense. Like there's 0:02:52.040 --> 0:02:53.840 some that are so low that you know, you can't 0:02:53.880 --> 0:02:56.680 hear it, but you can feel it. That's scrumbing feeling 0:02:57.040 --> 0:03:02.760 from from from and when sound hits a really solid object, 0:03:03.600 --> 0:03:06.120 it bounces it, it refracts off as some of it 0:03:06.160 --> 0:03:09.640 reflects back and uh, and that's where we get the 0:03:09.639 --> 0:03:13.359 whole echo effect. So when you're in the right kind 0:03:13.400 --> 0:03:16.160 of environment and you speak and you hear that echo, 0:03:16.320 --> 0:03:19.560 that's those sound waves bouncing back and coming back to you. Well, 0:03:19.720 --> 0:03:25.040 you can use this to find your way around an environment, right, Well, um, 0:03:25.200 --> 0:03:28.000 so where does sonar come from? Then we have to 0:03:28.040 --> 0:03:32.200 figure out exactly. Uh, really when that all started taking place, 0:03:32.280 --> 0:03:35.520 and I think it was really probably, I mean, people 0:03:35.520 --> 0:03:38.200 have been doing it for a long time. Yeah, you could, 0:03:38.200 --> 0:03:41.120 you could identify things and under the surface of the water. 0:03:41.280 --> 0:03:43.920 But why are you creating him? Because my favorite man 0:03:43.960 --> 0:03:47.120 of all time did some experiments with listening to sound 0:03:47.120 --> 0:03:53.200 through water. Okay, Leonardo da Vinci, we just finished talking 0:03:53.200 --> 0:03:55.720 about him a second ago, which I'll try and make 0:03:55.760 --> 0:03:58.440 sure that the podcast publish in the right order. But no, 0:03:58.640 --> 0:04:03.920 Leonardo da Vinci back in experimented with with listening to 0:04:04.320 --> 0:04:07.640 sounds through water. He would insert a tube into into 0:04:07.640 --> 0:04:11.160 water and put his ear to the tube like straw. Yeah, 0:04:11.480 --> 0:04:14.240 pretty much like a straw. Larger than a straw, Mr 0:04:14.280 --> 0:04:17.240 da Vinci. Why are you listening to your drink if 0:04:17.240 --> 0:04:20.800 you had a drinking problem? So, but yeah, he would 0:04:20.839 --> 0:04:23.240 use this to to kind of listen to uh to 0:04:23.360 --> 0:04:26.640 the two noises, with the idea that if you could 0:04:26.760 --> 0:04:29.400 create the right system, you would be able to detect 0:04:29.480 --> 0:04:33.000 when things were approaching through the water. Now, during da 0:04:33.040 --> 0:04:35.880 Vinci's time, this wasn't really that big a problem. Things 0:04:35.960 --> 0:04:38.400 usually approached on the water, and if they were in 0:04:38.440 --> 0:04:41.159 the water, they weren't really something you needed to worry about. 0:04:42.480 --> 0:04:46.800 The frogman of his day not not so effective, but 0:04:47.560 --> 0:04:50.280 getting all the way up to the eighteen or the 0:04:50.360 --> 0:04:55.239 nineteenth century, rather they hundreds uh you started to some 0:04:55.240 --> 0:04:59.960 some lighthouses would have underwater bells that would be uh 0:05:00.240 --> 0:05:05.000 placed around the area to warn ships of of hazards, 0:05:05.080 --> 0:05:07.960 so ships could actually listen as they approached land and 0:05:08.040 --> 0:05:09.880 they heard bells, they knew they were coming up on 0:05:10.000 --> 0:05:12.960 shoals and they could they could alter their course before 0:05:13.120 --> 0:05:19.280 running aground. And then uh in around nineteen sixteen. Uh 0:05:19.800 --> 0:05:21.960 it was an early passive so in our system. Will 0:05:21.960 --> 0:05:24.880 explain what that means UH in a minute. But they 0:05:24.880 --> 0:05:28.279 were using strings of microphones towed by ships, which is 0:05:28.560 --> 0:05:31.320 again something that dates up to the present in a 0:05:31.320 --> 0:05:35.920 different form. But by um and of course thinking back 0:05:35.960 --> 0:05:38.680 on it, that's you know World War one, right, the 0:05:38.720 --> 0:05:42.040 British and American scientists had developed an active so in 0:05:42.120 --> 0:05:44.600 our system, UM, you know that that was a big 0:05:44.600 --> 0:05:47.840 concern at the time because of course the German uh 0:05:48.200 --> 0:05:52.160 U boats were patrolling and it was some scary stuff. Yeah, 0:05:52.240 --> 0:05:55.640 actually it was. It was a very intimidating weapon, definitely. 0:05:55.640 --> 0:05:57.240 I mean there had been something sorry I keep coming, 0:05:57.880 --> 0:06:01.000 there had been submarines before that, but sure, the German 0:06:01.040 --> 0:06:03.440 U boats in World War One were a very effective 0:06:03.440 --> 0:06:08.640 way of taking control of the Atlantic Ocean and the 0:06:08.640 --> 0:06:11.480 shipping back and forth between the continents. So it's sonar 0:06:11.640 --> 0:06:14.200 was something that they were very rapidly trying to work 0:06:14.200 --> 0:06:17.680 out exactly. And it's funny because well, not funny, but 0:06:17.760 --> 0:06:20.640 it's it's interesting to me that really the the event 0:06:20.839 --> 0:06:24.000 that kind of started all this off wasn't World War One, 0:06:24.040 --> 0:06:27.640 because by then they were pretty far into it, but 0:06:27.640 --> 0:06:30.559 they did have an interest, yes, yes, to talk about 0:06:30.720 --> 0:06:33.039 To talk about how this really started off, you really 0:06:33.040 --> 0:06:34.960 got to look back to a certain event that happened 0:06:35.000 --> 0:06:37.920 in nineteen twelve. Oh really, and what was that event? Well, 0:06:37.960 --> 0:06:40.839 there was a little boat that happened to sink. Oh yes, 0:06:41.000 --> 0:06:45.240 that little boat. Yeah, yeah, don't they go um, my 0:06:45.320 --> 0:06:49.400 heart will go onto Yeah, the Titanic disaster, Titang disaster. 0:06:50.720 --> 0:06:53.640 Following that, that's when we saw the first patent for 0:06:53.880 --> 0:06:57.719 underwater echo ranging demands. So that was that was where 0:06:58.400 --> 0:07:01.160 the first patent was filed UM and it was filed 0:07:01.240 --> 0:07:03.800 at the British Patent Office by Lewis Richardson, who was 0:07:03.800 --> 0:07:07.359 a meteorologist UM and he he had come up with 0:07:07.400 --> 0:07:11.760 this idea of creating a way to locate objects underwater 0:07:12.120 --> 0:07:15.600 using sound. You would you would fire sound out, you 0:07:15.600 --> 0:07:18.600 would measure the sound that comes back, and through that 0:07:18.680 --> 0:07:22.520 you would figure out what was there, how far away 0:07:22.520 --> 0:07:25.160 it was, whether it was moving or not. I mean, 0:07:25.160 --> 0:07:27.840 these were all the concepts now back in nineteen twelve, 0:07:27.840 --> 0:07:30.840 they didn't really have a way of achieving this. He 0:07:30.840 --> 0:07:34.280 he panted the idea, but it wasn't until, like Chris said, 0:07:34.280 --> 0:07:38.680 around nineteen eighteen that we started to really see accelerated development, 0:07:38.760 --> 0:07:41.520 because then you had a wartime use for it, and 0:07:41.640 --> 0:07:43.880 it was really important to find a way to to 0:07:44.000 --> 0:07:48.320 detect those submarines, those U boats. Yeah, icebergs were were 0:07:48.360 --> 0:07:51.600 obviously concerned, especially in the North Sea and various like that. 0:07:51.880 --> 0:07:56.080 Um because you know, as as is in the case 0:07:56.080 --> 0:07:58.480 of many cliches, there is an element of truth in it. 0:07:58.600 --> 0:08:00.680 The tip of the iceberg really is, you know, the 0:08:00.720 --> 0:08:03.760 smallest right part, and so much of it is underwater, 0:08:03.840 --> 0:08:06.200 and you can't tell without some kind of device. And 0:08:06.240 --> 0:08:09.640 I think that's uh. The earliest, earliest sonar or the 0:08:09.640 --> 0:08:15.040 earliest echolocation devices were not very precise. In fact, they 0:08:15.040 --> 0:08:16.880 were so imprecise that they could tell you that there 0:08:16.920 --> 0:08:19.400 was an iceberg, but could not tell you where the 0:08:19.480 --> 0:08:22.280 iceberg was, So you you might know that there's an 0:08:22.320 --> 0:08:25.080 iceberg somewhere within a two mile radius of your ship, 0:08:25.240 --> 0:08:27.960 which is not entirely helpful, although I guess It tells 0:08:28.000 --> 0:08:30.400 you to keep an eye out so that you you 0:08:30.440 --> 0:08:32.520 don't see it just before you hit it, you know, 0:08:32.559 --> 0:08:35.440 you you know, to keep an eye out for for 0:08:35.520 --> 0:08:40.160 icebergs um. By the by the time World War two 0:08:40.200 --> 0:08:45.000 came around, that's when the because early sonar was really 0:08:45.080 --> 0:08:48.680 led by the British, they made the biggest advances in 0:08:48.760 --> 0:08:51.320 sonar technology. They didn't call it sonar. They called it 0:08:51.400 --> 0:08:55.719 as dick A S D I c UH and UH. 0:08:56.080 --> 0:08:58.640 The A S D was actually a code. It was 0:08:58.679 --> 0:09:01.959 It was so that the people outside of the top 0:09:02.040 --> 0:09:05.840 secret development wouldn't know what the scientists were working on. 0:09:06.440 --> 0:09:08.719 So people say, well, what does as DICK stand for? Well, 0:09:08.720 --> 0:09:11.160 it kind of stands for keep your nose out of 0:09:11.200 --> 0:09:14.400 it MR. So it wasn't really until World War two 0:09:14.400 --> 0:09:18.079 that the United States actually outpaced the British in this 0:09:18.160 --> 0:09:22.040 technology and uh, and that's when, you know, the term 0:09:22.160 --> 0:09:25.640 sonar started to pop up, and that eventually became the 0:09:25.679 --> 0:09:29.240 de facto term for the technology. Right right now, we 0:09:29.280 --> 0:09:32.920 should probably at this point go into the two basic, 0:09:33.600 --> 0:09:37.040 very very very basic types of sonar, so active and passive. 0:09:37.120 --> 0:09:40.000 Active and passive, and I think passive is the easiest 0:09:40.040 --> 0:09:44.240 one to explain yes, Basically you're receiving the sounds of 0:09:44.360 --> 0:09:47.840 the water around you. You're listening, yes, so simply listening. 0:09:47.920 --> 0:09:52.040 So passive passive sonar is where you have some sort 0:09:52.080 --> 0:09:55.720 of sound collection device, usually a hydrophone, which is just 0:09:56.000 --> 0:09:58.000 a microphone that you can use in the water. Right, 0:09:58.480 --> 0:10:01.520 you would have hydrophones play and you may have a 0:10:01.520 --> 0:10:05.480 couple of different passive sonar stations so that you have 0:10:05.600 --> 0:10:09.720 hydrogen phones directed in specific areas, so that way you 0:10:09.720 --> 0:10:12.040 can tell where the sound is coming from, not just 0:10:12.160 --> 0:10:17.080 that there is sound, and you listen carefully for any 0:10:17.160 --> 0:10:21.160 kind of indication of other activity in the water. And 0:10:21.880 --> 0:10:25.360 it's interesting because as I was doing my research, I 0:10:25.440 --> 0:10:30.280 discovered that that if you were a trained sonar operator, yes, 0:10:30.720 --> 0:10:33.720 and you heard a submarine. Let's say you're in a 0:10:33.720 --> 0:10:37.320 submarine and you heard another submarine, right, you could actually 0:10:37.360 --> 0:10:41.480 identify where that submarine what was from, based upon the 0:10:41.480 --> 0:10:45.160 sound you heard. Yes, that is correct, it is That 0:10:45.320 --> 0:10:48.320 is to me as phenomenal. Well, every uh, as I 0:10:48.400 --> 0:10:52.880 understand it, every ship of any kind, submarine or ship 0:10:53.000 --> 0:10:55.440 or you know, I guess boat depending on what's on 0:10:55.480 --> 0:10:59.600 the boat, has its own audio signature. Could be the engines, 0:11:00.360 --> 0:11:03.480 um or basically anything that's going on if they are 0:11:03.520 --> 0:11:06.360 electronics on board did make a noise if you know, 0:11:06.440 --> 0:11:11.760 fans things like that. Some those things can help identify, um, 0:11:11.800 --> 0:11:15.920 another vessel in the water to the listening vessel. Yeah. 0:11:15.960 --> 0:11:18.600 For example, in the United States, most of the submarines 0:11:18.640 --> 0:11:22.760 were operating on a sixty hurts alternating current power system, 0:11:22.800 --> 0:11:26.960 but in Europe they were operating on fifty hurts power systems. 0:11:27.160 --> 0:11:29.880 So just the the frequency of the sound would be 0:11:29.960 --> 0:11:32.080 enough to indicate to you whether you were listening to 0:11:32.160 --> 0:11:36.559 a US ship or a European ship. And uh, you 0:11:36.559 --> 0:11:39.160 couldn't necessarily if everything was running the way it should, 0:11:39.360 --> 0:11:41.400 you might not hear anything at all, or you might 0:11:41.480 --> 0:11:44.800 hear very little. Um. It was if you didn't sound 0:11:44.880 --> 0:11:48.080 proof all of your equipment, like if if the various 0:11:48.120 --> 0:11:53.360 elements weren't uh weren't insulated properly, then stuff would rattle 0:11:53.400 --> 0:11:55.600 and you could you could actually hear the rattling. In fact, 0:11:56.120 --> 0:11:59.360 one source I read said that, uh, you know, the 0:11:59.440 --> 0:12:01.800 location of a submarine might be given away by someone 0:12:01.840 --> 0:12:07.120 accidentally dropping a wrench onto the floor the deck. I guess, um, 0:12:07.160 --> 0:12:09.160 I assume they're decks and submarines I've never been a 0:12:09.160 --> 0:12:12.240 board one. Yes, I believe there are so. Yes, if 0:12:12.240 --> 0:12:13.719 you were to drop a wrench to the deck, it 0:12:14.320 --> 0:12:17.240 could create a sound that someone another sonar operator might 0:12:17.280 --> 0:12:18.560 be able to pick up and say, all right, they're 0:12:18.800 --> 0:12:24.160 they're support um. So it's it's a pretty interesting thing. 0:12:24.200 --> 0:12:27.120 And the passive sonar, by the way, was more important 0:12:27.160 --> 0:12:32.040 for submarines because if they use the active method, they 0:12:32.080 --> 0:12:35.640 would actively be giving away their location. Yes, that's because 0:12:35.760 --> 0:12:42.080 active active sonar systems are giving off a pulse of sound. Yeah, 0:12:42.280 --> 0:12:46.160 often called a ping. Yes, so you ping the sound 0:12:46.200 --> 0:12:49.840 out and uh, and then they wait for the sound 0:12:49.840 --> 0:12:53.360 waves to come back and based upon how long it 0:12:53.400 --> 0:12:56.679 takes and how much how strong the signal is, that's 0:12:56.720 --> 0:12:59.720 how you kind of determine what it is, your your hearing. 0:13:00.200 --> 0:13:04.000 You know how far away the object is, and you 0:13:04.040 --> 0:13:07.040 know what it might be. You know how many how 0:13:07.080 --> 0:13:09.480 many submarine movies have you seen where they do that 0:13:09.640 --> 0:13:13.040 tense moment where nobody's moving a muscle, they don't wait wait, 0:13:14.360 --> 0:13:16.160 you know, and there's just like you know, you watch 0:13:16.200 --> 0:13:19.559 the beads of sweat rolled down the submariner's faces. Yes, 0:13:19.640 --> 0:13:22.000 there's the there's the one that I quoted at the 0:13:22.040 --> 0:13:25.719 beginning of this podcast. Um, yeah, no, no, but there 0:13:25.720 --> 0:13:27.880 are many you know that that then that's the thing 0:13:27.960 --> 0:13:29.800 is you have to be very very quiet and that 0:13:29.920 --> 0:13:32.840 kind of a situation because any little thing can be 0:13:32.880 --> 0:13:35.040 picked up by the ping. And here's what's really interesting 0:13:35.640 --> 0:13:39.200 to me is that the ping is well really anything 0:13:39.200 --> 0:13:41.200 could be picked up by passive sonar. I know, I 0:13:41.200 --> 0:13:43.199 just want to make an Okay, I got you. I 0:13:43.280 --> 0:13:48.160 was about for the rhyme. I sorry, so active, but 0:13:48.160 --> 0:13:51.320 with the rhyme of an ancient you stopped at one 0:13:51.360 --> 0:13:53.880 of three. Chris and I will be back in just 0:13:54.040 --> 0:13:57.920 a moment to continue our discussion about sonar, but first 0:13:58.000 --> 0:14:08.240 let's take a quick break to thank ours. Answer the 0:14:08.320 --> 0:14:14.320 active sonar. The basis of that really rests in the 0:14:14.360 --> 0:14:16.840 fact that we know how fast sound travels through water. 0:14:18.120 --> 0:14:22.320 But we we do, but it's really complicated. You would think, oh, 0:14:22.400 --> 0:14:25.880 it's got to be some constant right, not exactly actually 0:14:25.960 --> 0:14:29.800 constantly constant. Yeah, The speed of sound traveling through water 0:14:29.880 --> 0:14:32.960 depends on several things. Depends on the temperature of the water, 0:14:33.520 --> 0:14:36.840 the salinity of the water, and the depth of the water, 0:14:37.560 --> 0:14:41.200 and all of these things affect the density of the water, 0:14:41.280 --> 0:14:44.360 which makes sense. Right. If you've got more molecules packed together, 0:14:44.840 --> 0:14:49.080 sounds going to travel faster through that because the molecules 0:14:49.120 --> 0:14:52.200 hit each other more quickly, Like it doesn't take much 0:14:52.200 --> 0:14:54.760 for a molecule they'll run into another molecule. The sound 0:14:54.800 --> 0:14:58.040 travels much much further and much faster, um if you've 0:14:58.320 --> 0:15:00.800 got them spread out the and they lose some of 0:15:00.840 --> 0:15:04.320 their energy as they are moving, and so it doesn't 0:15:04.360 --> 0:15:08.120 travels far and it doesn't travels quickly. So the rule 0:15:08.120 --> 0:15:10.800 of thumb is that it's four thousand three eight eight 0:15:11.160 --> 0:15:14.080 feet per second. And then you have to add all 0:15:14.080 --> 0:15:17.680 these modifiers in right right now, there are some some 0:15:17.880 --> 0:15:20.800 things that you can do. Uh. There is a system 0:15:21.560 --> 0:15:23.480 that I read about, the A N B q H 0:15:23.640 --> 0:15:28.040 DASH one speed of Sound measuring system, which is you know, 0:15:28.040 --> 0:15:31.840 a modern sonar system, um. But it evaluates the depth 0:15:31.880 --> 0:15:34.920 and temperature and salinity of the water to get an 0:15:34.960 --> 0:15:38.160 idea of how the speed of sound is going to 0:15:38.200 --> 0:15:41.760 travel through that particular water at the time. Obviously, that's 0:15:41.760 --> 0:15:44.120 probably a very expensive piece of equipment because it's doing 0:15:44.120 --> 0:15:47.640 those calculations for you. But that's what modern computing technology 0:15:47.680 --> 0:15:50.960 gets you. Um. But yeah, it gives you uh, you know, 0:15:51.040 --> 0:15:54.320 sonar technicians can use that equipment to get an idea 0:15:54.440 --> 0:15:57.480 of what's going on with a lot better accuracy, and 0:15:57.520 --> 0:16:00.760 it also helps them avoid being detected by other sonar 0:16:00.800 --> 0:16:04.080 equipment because they have an idea of you know, what's 0:16:04.200 --> 0:16:07.240 the current conditions are underwater where they are, right, So, 0:16:07.400 --> 0:16:09.560 if you're using active sonar, you might be using it 0:16:09.600 --> 0:16:13.880 for well if in wartime you would have ships and 0:16:13.880 --> 0:16:17.160 and even aircraft using active sonar to try and detect 0:16:17.200 --> 0:16:21.080 submarines and then drop depth charges down to to disrupt 0:16:21.080 --> 0:16:25.800 the submarines. Ah yes, uh so active sonar in wartime 0:16:25.840 --> 0:16:29.160 is often used by by vessels that can move fast 0:16:29.280 --> 0:16:31.840 enough so that it's not it's not a big deal 0:16:31.840 --> 0:16:35.520 about giving away your location like destroyers for example. Exactly exactly. 0:16:35.680 --> 0:16:38.280 If you're a submarine, you don't tend to use active 0:16:38.320 --> 0:16:41.840 sonar as often. Um yeah, especially when you're submerged in 0:16:41.880 --> 0:16:44.840 trying to avoid detection, because that's you can't move nearly 0:16:44.880 --> 0:16:50.240 as quickly as the enemy destroyers are coming after you. Right. So, 0:16:50.240 --> 0:16:53.000 so if you're also you could be using active sonar, 0:16:53.240 --> 0:16:56.160 not just in wartime, but also if you're mapping the 0:16:56.240 --> 0:16:59.400 ocean floor then you want you want to be as 0:16:59.480 --> 0:17:02.400 accurate as possible, which means you have to have you know, 0:17:02.480 --> 0:17:04.600 you have to factor in all those elements we were 0:17:04.600 --> 0:17:06.800 talking about before, the salinity and temperature and depth and 0:17:06.840 --> 0:17:09.600 all that. UM. If you if you're just using sonar 0:17:09.720 --> 0:17:12.040 as a fish finder, because there are plenty of of 0:17:12.600 --> 0:17:15.119 products on the market that do that, you don't have 0:17:15.160 --> 0:17:18.639 to worry quite that level of accuracy because you're not 0:17:18.720 --> 0:17:21.760 you're usually not talking about the same kind of distances 0:17:21.840 --> 0:17:25.720 involved that we're talking about, and usually the you know, 0:17:25.760 --> 0:17:28.399 the depth is not as big a factor. So really 0:17:28.640 --> 0:17:31.520 in that case, uh, you know, you could use a 0:17:31.560 --> 0:17:34.919 constant speed for the sound through water and not be 0:17:35.080 --> 0:17:38.160 so inaccurate. There. You're looking for schools of fish. They're 0:17:38.200 --> 0:17:40.280 going to be moving around anyway, so it's not like 0:17:40.320 --> 0:17:43.480 it's um, it's not like like the kind of precision 0:17:43.480 --> 0:17:45.960 work you need to do with these other elements. Right. 0:17:46.000 --> 0:17:48.240 Actually that that's one of the things that I found 0:17:48.240 --> 0:17:54.240 fascinating during part of the the sentar technicians training. They actually, 0:17:54.359 --> 0:17:59.919 uh are known to record things that are just natural sound, 0:18:00.520 --> 0:18:06.080 like the sounds of fish, um tectonic plates. I'm not 0:18:06.760 --> 0:18:08.600 I'm not sure what kinds of sounds does give off 0:18:09.040 --> 0:18:12.639 really low groaning ones, yes, kind of like my back. 0:18:12.960 --> 0:18:16.880 But that's but that's the the trick is you once 0:18:16.920 --> 0:18:20.119 they understand what those things are, they can eliminate them. 0:18:20.160 --> 0:18:22.400 They go, oh, well, that's just a large school of fish, 0:18:23.000 --> 0:18:25.640 you know. Oh that's you know, an alien spaceship that's 0:18:25.640 --> 0:18:30.440 crashed underwater, that kind of stuff. Um, I make a joke, 0:18:30.640 --> 0:18:33.440 but no, that that that Uh. I was wondering about 0:18:33.440 --> 0:18:36.199 that when I was reading about civilian uses for so 0:18:36.280 --> 0:18:37.919 in our technology, and I was thinking, wow, how do 0:18:37.960 --> 0:18:40.560 they know, you know, what is a school of fish? 0:18:40.560 --> 0:18:43.639 And obviously if you're on a lake and it's it's 0:18:43.640 --> 0:18:46.080 probably going to be the stuff that's moving around underwater. 0:18:46.240 --> 0:18:48.879 It's not likely to be an enemy submarine. But you know, 0:18:49.359 --> 0:18:52.640 detecting a fish versus you know, a snake or some 0:18:52.680 --> 0:18:57.879 other type of monster, we've gotten very silly, very quickly. 0:18:58.119 --> 0:19:00.639 Well no, I mean people have been used saying that 0:19:00.720 --> 0:19:02.919 kind of equipment to try and determine whether or not 0:19:02.960 --> 0:19:06.480 there are yeah, so our equipment. Yes, there are plenty 0:19:06.680 --> 0:19:09.879 of monster hunters who have tried to use like a 0:19:09.920 --> 0:19:14.200 fish finder, yeah essentially. But that's the thing is that there. 0:19:14.200 --> 0:19:16.760 There are schools of fish in Locknest and schools of 0:19:16.760 --> 0:19:20.360 eels as well, So you get a school of fish 0:19:20.480 --> 0:19:21.840 or a school of eels that's going to give you 0:19:21.880 --> 0:19:23.480 a reading. And then people say, hey, look there's a 0:19:23.480 --> 0:19:26.880 monster down there. Not necessarily and I have to say, 0:19:26.920 --> 0:19:29.000 you know, I've mentioned before in the podcast that I'm 0:19:29.000 --> 0:19:32.800 a skeptic. Out of all the things to be skeptical about, 0:19:32.880 --> 0:19:35.160 the lock best monster was the one I held onto 0:19:35.200 --> 0:19:37.959 the longest because I want to believe it's real. I 0:19:38.040 --> 0:19:41.680 don't believe it's real, but I want to so badly. 0:19:43.480 --> 0:19:46.439 UM and a cottage on the shore. There's a shadow 0:19:46.480 --> 0:19:50.480 on the door. No different kinds of sonar okay, side 0:19:50.520 --> 0:19:55.000 scan center UM. This is a device used to find 0:19:55.480 --> 0:19:57.680 objects on the sea floor and figure out what they are. 0:19:58.160 --> 0:20:01.120 They usually have a tow fish or a tow body, 0:20:01.240 --> 0:20:05.520 which is a UM basically sophisticated device that goes in 0:20:05.560 --> 0:20:08.240 the water and is towed behind the ship, and a 0:20:08.240 --> 0:20:11.399 device that processes the signals on the top UM. What 0:20:11.480 --> 0:20:15.720 happens is they use the the sound energy which is 0:20:15.760 --> 0:20:19.359 transmitted in a fan shaped pattern and goes about a 0:20:19.400 --> 0:20:24.440 hundred meters down or so. Basically, they used the information 0:20:24.440 --> 0:20:27.879 that comes back to create an image of what's on 0:20:27.920 --> 0:20:30.119 the sea floor. So if they get a really strong 0:20:30.200 --> 0:20:35.199 signal um back, that appears as a light image on 0:20:35.240 --> 0:20:40.240 the screen, whereas weaker signal would show darker images. So 0:20:40.320 --> 0:20:42.919 you get uh, sort of a black and white image. 0:20:43.080 --> 0:20:45.720 I don't know if it's actually black and white, because 0:20:45.720 --> 0:20:48.160 I was reading copy and it might be photo bright 0:20:48.200 --> 0:20:50.520 green and dull, right right, But you can get an 0:20:50.520 --> 0:20:54.000 idea of what the the bottom of the area you're 0:20:54.000 --> 0:20:55.439 looking at. I guess it could be a lake or 0:20:55.480 --> 0:20:58.640 the ocean. Um they don't they don't offer the same 0:20:58.720 --> 0:21:02.439 kind of depth information as the military would use to say, oh, 0:21:02.480 --> 0:21:05.000 well we you know, we're about to run around. It's 0:21:05.040 --> 0:21:08.760 not the same kind of application of sonar. Also, we 0:21:08.800 --> 0:21:11.680 should add that at certain depths, once you get really 0:21:11.720 --> 0:21:13.960 really deep, the water gets so dense that it can 0:21:14.000 --> 0:21:17.919 refract sound waves. So you you start to lose the 0:21:17.960 --> 0:21:21.479 ability to really map the ocean floor with sound because 0:21:22.560 --> 0:21:26.080 the water itself is so dense that it's it's it's 0:21:26.160 --> 0:21:29.440 mucking things up. Also, I guess I should go ahead 0:21:29.440 --> 0:21:31.520 and mention as well. We've talked a lot about the sonar. 0:21:31.600 --> 0:21:34.520 The sonar really has three main elements to it. Yes, 0:21:34.560 --> 0:21:38.320 there's a transmitter which transmits the sound right right, we 0:21:38.320 --> 0:21:40.640 didn't really talk about it, but there's a transmitter that's 0:21:40.680 --> 0:21:44.040 that's what passes on the signal. UH. It's an electric 0:21:44.080 --> 0:21:47.160 signal that goes to a transducer. Now, transducers, what they 0:21:47.200 --> 0:21:50.040 do is they convert one kind of energy into another 0:21:50.119 --> 0:21:52.920 kind of energy. In the case of sonar, it's converting 0:21:53.040 --> 0:21:56.760 sound electricity rather into sound, right active for this is 0:21:56.760 --> 0:21:59.960 for active sonar clearly. And then you've got to receive 0:22:00.080 --> 0:22:02.600 or that receives the signals when they come back, um 0:22:02.640 --> 0:22:06.400 and and then you usually have a display. So there's 0:22:06.400 --> 0:22:10.680 a transmitter, transducer, and receiver. This is for again active sonar. 0:22:10.880 --> 0:22:15.439 With the passive sonar, you just need receivers really microphones, hydrophones, 0:22:16.000 --> 0:22:19.479 um and and there are plenty of stationary UH sonar 0:22:20.040 --> 0:22:24.679 UH stations, and I guess stationary stations, thank you, Jonathan, 0:22:24.720 --> 0:22:27.360 you're both repetitive and redundant. But at any rate, there 0:22:27.359 --> 0:22:30.280 are plenty of these in the ocean. The lots of 0:22:30.280 --> 0:22:34.679 different militaries have them station stationed at different spots along 0:22:34.720 --> 0:22:40.399 the coast to detect things like possible incoming submarines, that 0:22:40.480 --> 0:22:42.800 kind of thing. We have a bit more to say 0:22:42.880 --> 0:22:45.880 about sonar technology, but before we get to that, let's 0:22:45.920 --> 0:22:56.800 take another quick break to thank our sponsor. There was 0:22:56.840 --> 0:23:00.760 a sound detective in n It was actually detected several 0:23:00.760 --> 0:23:05.199 times over the summer of U in the Pacific Ocean 0:23:06.080 --> 0:23:11.240 by by a hydrophone array, and the sound was a 0:23:11.359 --> 0:23:17.080 very low frequency sound generated over a pretty extended uh 0:23:17.480 --> 0:23:21.520 time frame several I think it's several minutes long, and 0:23:21.600 --> 0:23:26.679