Testing the sound mirrors that protected Britain

[@TomScottGo]

I've wanted to make this video for literally four years, and - thanks to the RAF team - all the pieces finally came together. Do go check out my history of radar video over on their channel!

[@sop3191]

Tom Scott I live in Greatstone, which is a 5 minute walk to there

[@tizer33]

I used to play on these as a kid.

[@MattFowlerBTR]

Air-grabs aren't automatically a problem, if the pilot is co-operating and the person doing the grab can keep their fleshy bits away from the whirly bits. Definitely would be more of a risk with carbon-fibre props because those things are savage little vampires. I've air-caught our Phantom 4 many times, if the ground isn't conveniently flat and stable. But it is definitely something that needs care and *can* go wrong for sure.

[@benketteridge9150]

There are also working parabolic sound mirrors at the Joddrell Bank observatory, though they are more for science education these days than any kind of military application.

[@danieldc8841]

How did you option permission to fly your Phantom there? Did you have to namedrop?

[@charliefoxtrotthe3rd335]

There is a bar in Vegas, I think it's the Rio, that is perfectly round with a really high domed ceiling. You can sit on one side and talk in a soft voice to a person sitting on the other side 30 feet away and they can hear you just like you're sitting next to them leaning over to whisper in their ear. It is the coolest thing ever. When it's really busy and full of people the effect is cancelled and it just sounds like a normal bar. But in the morning when it's empty we would sit on opposite sides and have a conversation. So cool

[@henokhjosandraehesperus7369]

Please give me more details about the place, so I can look it up on the internet. I'm really interested in knowing more about this kind of structure.

[@comedyqwerty8772]

@@henokhjosandraehesperus7369 google "whispering gallery"

[@niilo5639]

In Finland we have that thing too

[@MichaelJONeill333]

I want to try!!!!

[@TheSharity]

theres a spot in the NYC subway system that this works as well.

[@Liggliluff]

When you increase the volume to hear it better. Tom: *_BRING HER IN!!!_*

[@Cr42yguy]

Missed opportunity to fly through the hole in the wall :P

[@Kanbei11]

BRING ON THE WALL!

[@benford1726]

@@Kanbei11 and now I want to see TechDif do Hole In The Wall

[@rchaffer]

I like how it's quiet, so we turn up the volume to hear the drone hum, then Tom screams "NOW TAKE IT SIDEWAYS!". You owe me new underwear, Tom!

[@lawrencecalablaster568]

These are utterly amazing :) thanks so much for finding and visiting places like this.

[@ArifRWinandar]

So in a fantasy setting, this wall can be used to detect incoming dragons?

[@pintpullinggeek]

If you could isolate the frequency of a dragon's wingbeat then maybe. But no use if they were gliding.

[@NotAMathGuy]

Arif R Winandar what about the flying wizards?

[@krashd]

Well old wizards are known to be quite chatty so again you would just isolate the frequency of their voice and listen for their grumpy mumblings.

[@NotAMathGuy]

Rob Fraser hmm how about ye thinkin about the good ol witches in thy forests?

[@carlosandleon]

No, well if the flapping makes no maybe

[@SomeThrillingHeroics]

Although they did quickly become obsolete, they gave the British more than a decade of practice pinpointing targets based on a network of interconnected monitoring stations. It's interesting to think that what made Britain's technologically inferior radar systems more effective in practice than the German systems... was an even more technologically inferior system.

[@agimasoschandir]

I was to understand the British radar knowledge was well in advance of what the Germans developed. I have not read otherwise

[@SomeThrillingHeroics]

The German "Freya" radar system used a shorter wavelength than the British system, so lead to smaller radar antennas that were easier to position, as well as capable of detecting smaller objects reliably, so was in that respect technologically superior. (Admittedly, one problem with reliably detecting smaller objects was that it allowed the British to more effectively use chaff as a countermeasure but, still, the German systems were capable of detecting these smaller objects, even if its operators would have preferred it didn't).

[@RhodokTribesman]

Eh, Idk if the mirrors helped with "practice." It's simple trigonometry, really

[@OktoberSunset]

@@RhodokTribesman The more important part is the information management. Collecting all the reports from individual stations and then assembling a picture of where all incoming planes are and where they are going in real time to allow a fully co-ordinated response is the most important part of the system, and what the Germans failed to do until late in the war.

[@RRW359]

@Boring Name I don't think OP is saying British Radar was inferior. OP said one of the things that made British Radar superior was practice from these mirrors, which are inferior.

[@richardpike8748]

Isn't it amazing how many different obscure technologies were designed and even built or used but were very quickly (in just a few years or so) surpassed by superior technologies which are much more commonly known? Thank you Tom Scott for letting the internet know about these fascinating reminders of niche obsolete technologies. I've found them quite interesting.

[@J75Pootle]

My favourite example of this is in guided missiles. During WWII the US wanted a way to have missiles that would home in on their target, so they hired a bunch of behaviourist psychologists to train pigeons to peck at the dark object on screen (enemy ship on the water) to help keep the missile pointing towards the ship. Unfortunately (or fortunately for the pigeons) they invented mechanical guidance systems before the project pigeon could complete

[@alexc4300]

the modern progression from VHS/BETAMAX, Laserdisc, DVD, DVD-DL, Blu-ray, USB, streaming is another fine example of prompt obsolescence.

[@DarthTella]

It sounds like Tom caught a whole bunch of bees.

[@SirBlueWhale]

NOT THE BEES!

[@anchovybushwack472]

123rd like

[@steckelton717]

I am super happy that you coverd this amazing pice of technoligy that came out of necessity and still was able to work fine enough. I love documentaries and in one of them, he Sound Mirrors came up and they were fascinating to me, because they were so...."simple". They are ingenious for how simple build they are. Thank's for sharing this :)

[@jakemurphy9536]

Fascinating video, Tom. Some years ago I watched a documentary about this, but, unlike you, the maker did not sound test them, which left me, and many others, wanting just what you have done here. Many thanks.

[@JackofSpades6]

“There’s not a lot of technology that can survive 90 years...” Nokia: hold my beer

[@DanielsPolitics1]

“The West Coast Mainline has entered the chat” “The Regents Canal has entered the chat” “The Ribblehead Viaduct has entered the chat”

[@divakarchouhan612]

The AC current has entered the chat

[@friendlypiranha774]

@JackofSpades6 - 100 years ago Nokia was a toilet paper manufacturer and 50 years ago it made car tyres. Very interesting how it got into cellular telephones.

[@whyjnot420]

These are easily one of my favorite bits of overlooked tech from that time. Always great to see someone talk about them.

[@56Seeker]

If you're into the history of science, Tom, it's worth looking at how & why each great power in WWII went their own way with radar: Britain used it to create a virtual reality battle command, USA used it for proximity fusing, Germany used it for navigation and Japan tried to make a death ray (by '45 they could kill a rabbit at 100 yards).

[@backwashjoe7864]

What did the French use their radars for?

[@pintpullinggeek]

So those mirrors have been about 15 miles away from me most of my life and I never knew they existed. The Marsh has so much history in it!

[@Cadwaladr]

I've heard of those things before, but I never knew exactly where they were. Took me a little while hunting around google maps (I know I could just do a search, but that's no fun) but I found them. that low white dome and tower thingy in the background at 2:13 helped me figure it out. Good times.

[@matthewboswell2494]

Dungeness nuclear powerstation at 2:27 might have helped too

[@paulsengupta971]

If you fly into Lydd airport, you fly over them.

[@Michael0100]

I live just down the road in a small town called Lydd, I see them every day on my way to Folkestone, near Lydd airport, hell I even work in the restaurant at the airport, it awesome to see a video so very close to home! You can even see the local water tower in the distance and the town I live in, in the far distance. I've heard all sorts of things about World War I / II from the workers, passed on tales and some no-sense on the side, there's even a Nuclear Power Plant just a short journey down the road at Dungeness.

[@broosheidmedia]

Old comment, but hello fellow SE Kent person!

[@Seapin1]

Here in Melbourne, Australia, we have a science museum called Scienceworks. They have this fun setup where there are 2 dishes set up about 100m apart pointing at each other. You can have a conversation at normal voice levels with someone at the opposite end. It's really cool. There's also a planetarium there where the acoustics of the domed ceiling means whispered conversations can be heard from anywhere in the room.

[@uscitizen5656]

Too Cool! I had never heard of these before that I remember and I'm 68 over in the US. Thanks all!

[@LoveOfMules13]

I lived in a dorm building that had a very similar parabolic dish shape. The entrance and all of the dorm room windows faced forward in the "dish", and my room/window happened to be very close to the center. The windows were soundproofed surprisingly well, but if you cracked them even a little you could make out conversations people were having at normal volume ~200 feet away, across the street... if you weren't being deafened by a bunch of other street noise.

[@matthewmicallef3811]

While this design didn't see much action in the UK, this device saved many lives here in Malta. We still have these dotted around our northern coast. One in particular still survives in very good condition.

[@ReductioAdAbsurdum]

I know it's tempting to grab those phantoms out of mid air, because they appear so stable, but those blades are extremely dangerous. No worth losing fingers over.

[@krashd]

That's probably why Tom grabbed it by the landing strut and not one of the spinning blender-like things...

[@MisterVonnels]

@@krashd Drones like the Phantom can make automatic adjustments, if you grab it wrong it may try to adjust itself and pull away or push towards you. You could cause it to tilt downwards towards your hands or face.

[@fallingwater]

Consumer drone props will draw blood, but won't cut fingers. They're made of plastic and will shatter before going through a significant amount of you.

[@EddieB-ready]

@@fallingwater but they will leave scars

[@DaveDexterMusic]

@@fallingwater If they draw blood, then they can cut fingers.

[@ovalwingnut]

Once again, the fantastical imagination and resourse of our UK brothers. You RoCk. Cheers from the US

[@Vyrus__]

The drone getting angry when Tom grabs it is hilarious

[@spencerlam9361]

The soundwaves length is such that 1/4th of that length is larger than any imperfection on the surface caused by old age. From the perspective of the sound the mirror is very smooth and shiny giving a crisp image

[@allanmurray647]

This channel always seems to amaze me

[@davidbuschhorn6539]

That's a really good, clever tool! Simple and effective. Low tech and effective :-) It transmits nothing so the enemy would never know how you were locating their planes. If you had two of them a few miles apart you could triangulate distance as well as direction, but not elevation. Good enough to scramble defense aircraft though. The more I think about this, the more I like it :-)

[@alexanderf8451]

They might notice the huge concrete walls.

[@davidbuschhorn6539]

From 27 miles away they'd notice a new concrete structure that could look exactly like a wall/building? At night?

[@KuraIthys]

You could detect aircraft using optical telescopes, but it's not that effective unless the telescope is very good. This is a very low tech solution, but it'd do alright. Not against modern aircraft, because those travel faster than the speed of sound. (in other words, you'd not pick them up until they'd already passed you. - if they were headed in your direction - you would pick up one flying parallel to the detector, though your detection would be some way behind it's actual location, but you'd be able to estimate speed from how quickly it moves across detectors, and from that you could estimate how far ahead of it's apparent current location it actually is.) This would work really well with some computer support of course, but still... It has a lot of downsides too.

[@tapist3482]

This is a high intelligence, low technology solution for passive detection. Now we have a high intelligence high tech solution: thermal optics.

[@efulmer8675]

If you had a third wall that was at an angle to the other two and more spherical you could get elevation that way.

[@cesariojpn]

Perfect place for a Mirelurk Den.

[@dxkaiyuan4177]

Got my scoped .44 ready to shoot them in the face

[@Tailspin80]

Stonehenge was actually a prototype sparse array technology for 3‐D sonar imaging designed to detect alien spaceships. It didn’t work that well and was repurposed as a tourist attraction.

[@nolesy34]

Finally some answers!

[@dwnetwrok]

Love how this is professionally shot but he’s still out of focus

[@franklinegbuche7097]

That's smart engineering.

[@Whizzer]

Fascinating, as usual!

[@howardsimpson489]

Here in Hawera, a small town in NZ, there is a large pond with two sound mirrors on opposite banks several hundred metres apart. A whisper in the focal point in one can be clearly heard at the focal point in the other.

[@187sdv3]

Where exactly? Im tryna look at it from google maps

[@nataliefleming3630]

“Hmmmmm big ears” - Sam O’Nella

[@carter1807]

-the country’s elders

[@davefave4351]

I've seen them up close and personal during a long stroll whilst at a weekender at Pontins, Camber Sands. 100ish years later and the pace of change from high to old tech increases exponentially...

[@rorrt]

Pffft. Radar is a myth! Carrots are all you need!

[@Phourc]

Oh wow, that's a reference.

[@drivesthecar3247]

Not a lot of people know that!

[@FrozenLavaDragonProd]

What reference is that?

[@TechnoHackerVid]

_Clever reference_

[@youliahadzhidimova5260]

Just googled it. Yeah, ok. It is a clever reference.

[@jcs3330]

As a youngster back in the 70/80s, I used to walk past this site from Dymchurch and always wondered from a distance what they actually were.

[@fvlse_]

This dude just embodies anxiety. He looks like he’s constantly under threat.

[@woozy7405]

lmfao

[@acorr14]

In Australia, at one of the radar dishes you can visit (Can't recall the name, but it helped with the moon landing) they have two large concrete dishes out front, 150m opposite each other. If you talk into one, a person can hear you at the far side :D

[@bobfal]

I'm sure a lot of work went into that Tom, just to say it was well worth it!

[@Rocklobster6285]

We've got a much smaller version of one of these at my university, if you whisper at one end of the wall you can hear it perfectly clearly on the other

[@HippoDrones]

that is bloody awesome mate, so jealous you got to perform this experiment! :-)

[@BobMcCoy]

*Do they reflect bad music?*

[@rowgli]

_Bob McCoy no, but they do employ some focused hocus pocus

[@1_1bman]

this is so sad sound mirror play despacito

[@NathansWargames]

" it's september 2049. ww3 has started, the uk is being overrun by Russians and they are closing on on invading our last hope, sound mirrors reflecting Justin Beieber music in the direction of the incoming Russians work, they scramble never to be seen again "

[@taliakellegg5978]

Depends on what kind of music

[@hhhfff7953]

Play some XXXtentacion and see.

[@upbeat_garbage0308]

At the science works museum in Melbourne Australia, they have something similar on a smaller scale where they have two dishes facing each other roughly 100m apart and when you speak into it the person at the other dish will hear it. It’s quite cool

[@kinto4135]

We got much smaller sound mirrors (like these round ones on the side) near my hometown, but these are just to experiment with sound waves. Nevertheless, it's really interesting to play with them!👌

[@jur4x]

there are few left between Dover and Folkestone. Much smaller though.

[@nuclear_war_games]

These were also great for listening to The Prodigy

[@sinom]

*DON'T TRY THIS AT HOME* Grabbing a drone is never a good idea. Even when it's stationary.

[@RobertSzasz]

Sinom they get angry and soon the whole swarm is after you.

[@dreamystar1117]

@Edwin Cheesecake It probably means when the drone is stationary in air, where the blades are rotating fast and will possibly leave you scars

[@AmatuerHourCoding]

FYI consumer drones can't break skin. This is nonsense

[@danielr8257]

@@AmatuerHourCoding yes they can. Especially the one they were using. Very heavy drone, very fast propellers

[@unfunny2258]

Bewsted do you have a brain?

[@giantfisher]

Thank you so much for all your effort!!!!

[@elcajondavid1]

The Brits came up with some interesting ideas that actually worked especially during WW2.

[@beemer9108]

That is absolutely brilliant. Really, a clever way of detecting aircraft before it's coming. Sure, radar was invented, but this was ahead of it's time. If something _had_ happened that required this system, they would be the only ones in the world that had it, and it's super well thought out, too. Amazing.

[@elmattbo2540]

I’ve been meaning to visit these things for ages! Possibly with a drone, but I thought better of it...

[@DarrenBates]

Ah new Tom Scott. Nice bank holiday treat.

[@NicoSmets]

I've seen BMX'ers in that dish :0)

[@Minifig666]

Played with some of these in the north east, but didn't really know much about the design - very cool to see it demonstrated with an actual aircraft too. Thanks Tom and co!

[@sloonzz1012]

And it was here in these skies that the Luftwaffe was defeated, not just by brave airmen in fine aircraft, but by invisible beams of electromagnetic energy which could see further than the human eye. The great British secret weapon, Radar.

[@Schmidtelpunkt]

It's just... the hands...

[@pintpullinggeek]

Did anyone else just hear Sir David Attenborough?

[@krashd]

Ahh, David Mitchell doing his impression of Stan from the Monkey Island games. Love it!

[@ggor06]

This channel is so interesting. You deserve more!!!!

[@DannyRice01]

I can't believe that phantom 4 hit a tree, did a full fov quad flip then saved itself. Astonishing technology now that shows how far we have come from giant concrete walls with microphones

[@MA1DENR0CK]

Not too far away from my home town of Rye. My grandfather worked at Dungeness for around 20 years. He told me all about the sound mirrors when I was a kid. Great stuff.

[@dirtychinchilla]

The ways in which we defended our country are incredible. I’m no nationalist. Right now you could call me a globalist. But when I see stuff like this I couldn’t be more proud of the UK

[@michaelwinter742]

Tom - You should write a book about where to go on science-themed dates.

[@DomBurgess]

Great video - had no idea these existed, so simple and yet so effective.

[@kristophia7310]

it's been four years scence tom made this video and whoever is reading this did you watch on release day?

[@Vyker]

This guy is just brilliant! Thanks for bringing this stuff to our attention!

[@hushkit2119]

Coolest channel on YT

[@heyimamaker]

The Alberta legislature building has a fountain in the middle of a room, on the second floor there is a arch way that reflects the sound and gives the impression that you are standing in the fountain.

rip drone at the end 😂

[@TheCptCoy]

Right? That poor drone... Someone should have taught him how to do a catch landing before trying to get that shot.

[@cpufreak101]

based on other comments, the specific drone used has protections in place to allow that to be done

[@TheCptCoy]

No, just because the motors can endure more stress doesn't mean they should. It's obvious they planned the shot one way as Tom just pulling gently on the drone and them thinking it would glide over like an air hockey puck. They forgot that the drone will try as hard as it can to maintain not just its altitude but also it's lateral position. So instead of remaining level the drone tilts the OPPOSITE way and attempts to play tug of war with Tom. This exerts a perpendicular force onto the propellers and causes way to much torque as the motors are spinning at full speed. It's nice that the channel is doing well and they don't have to worry about potentially replacing or fixing the drone, but to us thats a $1000+ drone that he is treating very badly. Also, if you are only going to comment with what you have read "based on other comments", isn't that sort of useless? If you don't have firsthand experience, why correct others with firsthand experience based on some random comment claiming this is okay?

[@alastair6320]

Just got a massive nostalgia trip from when I watched the coast episode about them

[@AbbreviatedReviews]

How Can Sound Mirrors Be Real If Our Ears Aren't Real.

[@mastershooter64]

ah yes the stoner

[@McRocket]

Fascinating...I had never even heard of this (to my knowledge) before this video.

[@BSG99]

You can stand at either end and have a conversation with someone ;)

[@DigitalVoices]

BackstageGerm 99 we did!

[@phorty2]

Awesome video Tom! I love the way you set out the information you present your information!

[@kmineww5801]

I go on holiday here. I know I Boy who swam across the lake to get to them XD

[@iainmaclean3879]

apparently they had these on Malta during WW2 and they were so sensitive they could pick up the noise of aircraft engines starting up on the Italian airbases in Sicily, over 50 miles away

[@Quantum-Bullet]

Can we also have lenghts indicated in meter?

[@bluerizlagirl]

QuantumBullet That wall is about 60 metres long.

[@MateusSFigueiredo]

Please.

[@treeherder42]

So I'm watching this with wireless headphones. At around the 1:40 mark when Tom says to listen, in perfect timing my headphones screamed out "BATTERY LOW".

[@LunarDelta]

Obsecrete.

[@CatheteriZedEYE]

2:59 Tom grabs a bee mid flight "YOU MONSTER"

time to start a kick starter for sound mirrors. I'm sure it'd make millions, just like all those other impractical and unfeasible ideas.

[@ExEBoss]

The only difference is that sound mirrors are feasible and practical, albeit obsolete by radar and other modern technology.

[@MrD8n]

Hope you had fun in the Romney Marsh!! Certainly kept me entertained my whole life

[@JJones-gw9vy]

War breeds such interesting technology

[@mapesdhs597]

It also breeds the best, but we musn't talk about that. Now then, back to watching TV and playing computer games. :)

[@archdukefranzferdinand567]

@@mapesdhs597 I think the trade between a slower development of technology and the deaths of millions might not be worth it

[@ebi3954]

this video is a work of art

[@johnhili8664]

Here on the island of Malta we have a similar sound mirror which was built by the British forces to detect aircraft coming from Sicily during the second world war it is the only one outside the UK and still in good condition!!

[@joelthomas1585]

Who dislikes the video before there has even been time to watch the whole thing?

[@FoxDren]

the germans

[@joelthomas1585]

I should have known.

[@scythal]

Damn it Jerry!

[@dygi7631]

You need to learn an English Edit: oh now I get it, fair enough

[@TheCptCoy]

Disliked for pulling on the drone while it was still hovering, he put so much strain on those motors.

[@DonFatherTrump]

I have experienced the reverse. I live a few miles from a hospital and occasionally the helicopter is many times louder. One of the landing pads is right next to a big ramp that goes up two stories with hospital structure on the other side. It forms a cone aimed in my direction.

[@ChrisHutchinson]

I watched tallorder BMX ride here.

[@tankeras94]

was looking for someone commenting this

[@stephfh]

Ah, that's why that spot looked familiar. :D

[@campbellrocksagain]

Tom Scott your videos are awesome

[@miseltoe1]

I don't know what sound I'm supposed to be listening for 😅

[@michaelcarman9820]

miseltoe1 the electric motors buzz, fairly high pitched

[@STARRSHIP]

The buzz :)

[@ToTheGAMES]

WWWWWWZZZZZZZZZZZZZZZZZZWWWWWWWWWWWWWZZZZZZZZZZZZZZZZZ ;-)

[@staberas]

the bees in the background

[@Outfrost]

The sound of your mum yelling "put on your headphones!".

[@Paul-Weston]

At the base of the Acropolis in Athens there's a theatre with the same effect. Wherever you sit you can perfectly hear the actors talking on the stage.

[@BanditRants]

Hey Tom, you wanna collab?

[@tonyrawmen4966]

Godly edits Bandit

[@branchy2279]

You don’t really wanna ask to collaborate in the comments it’d be better to send him a message

[@rodigoduterte9192]

BanditRants hmm... I'd subs you for that interesting tumbnail

[@mepizzasmangled]

Is there a creator you didn't spam this too today?

[@mepizzasmangled]

I suggest a more professional approach when reaching out to creators rather than spamming every one of them to better yourself. Your editing skills are great but you're acting desperate and creators like tom clearly wont want to associate with that sort of personality..

[@AirborneSurfer]

Very interesting! I've seen these before, but never quite in such detail! Thanks, Tom!

[@fdavillar]

"foot"? Is that why UK want BREXIT??

[@Jabber-ig3iw]

Fernando Davillar as a nation our choice of using metric or imperial is completely random, for instance we buy fuel by the litre but measure our fuel economy in miles per gallon.

[@jur4x]

UK gallons mind you :) 4,5L not tiny US gallons that are only 3,7L

[@ashleigh.]

4.5L and 3.7L*

[@wildwalkeruk]

these are cool, I have a customer in Malta, and their office is right next to one of these. Really cool engineering.

[@TheKirbyT]

This is completely fascinating.

[@macmcleod1188]

This was awesome!

[@matthewpiatt]

As a sound engineer with a fascination with acoustics, I greatly appreciate this video.

[@lucaswallace7476]

Tom Scott: *Grabs drone angrily.*

[@NorthWestOutlaws]

We have one in Sunderland, Tyne and Wear, still working perfectly well.

[@Moertn2311]

You really make very interesting videos. I love them

[@RealSalica]

Your videos are always so interesting !