Fire Engine siren demonstrates the Doppler Effect

[YuTe3712]

Just watched this video in my GeoPhysics class today.

Everybody went "WOAH!"

We watched it again.

[melikecookie]

republic poly gt no other videos to show ,so dumb

[Spudst3r]

Very good example!

[htden]

As it approaches: Frequency observed = Frequency of Siren (velocity of air / velocity of air - velocity of truck)

As it leaves: Frequency observed = Frequency of Siren (velocity of air / velocity of air + velocity of truck)

So long as the truck wasn't accelerating in it's motion (velocity was constant), the frequency shift was constant (neither increasing nor decreasing). You can observe this in the video between frequency as it approaches and leaves. The switch is instantaneous. Neat

[PumpManufacturers]

nice example

[TC53227]

GO TOUCH A BIG FAT VEINY COCK!

[Lammedreng]

Aaaahh......don't we all love science?

[cowcowpingpong]

Republic poly lead me here

[saljooghi1]

@cowcowpingpong typing in 'The Doppler Effect' lead me here

[MistryWho]

lol, my prof showed this in physics.

best example ive seen

[Crashdance22]

This also demonstrates the theory of relativity between the truck and the observer. To the driver, a certain amount of time passes in a single cycle of the siren (high followed by low). But because of time dilation, the observer holding the camera first hears a higher frequency followed by a lower one, making it appear that the siren is operating faster when approaching, and slower when evading. Bam, relativity at work in an instant.

[psylover1991]

this is cool, never herd about doppler effect before (im not a science kid), and i like it a lot,very interesting :)

[voicetube]

Excellent, thanks for posting!!

[desmodronic916]

Niii Nooo Niii NOooo Niii NOOO niii NoooOo Niii Nioouuu Nooo Nooou Noooo Noooou....

[16goarmy]

why doesnt anyone else use those sirens anymore

[ImRatherTall]

@16goarmy Cornwall FRS still do, same truck too!

[cedarpaw23]

that's so cool!

[alexanderbrowning]

Nice DopplerEffect.We can enjoy DopplerEffect everywhere on this planet.It's wonderful,isn't it

[fjanton83]

this most be the funniest sound in the world

[ladiestreat27]

@fjanton83 lmfaooooo

[KooKas2oo8]

Nice. Pretty old firetruck you got there :p

[sool32]

Very nice example, it really highlights the change in frequency. :)

[fcofelixx]

nice example

[seeebitaaaxproo]

the

[scorpia12345]

does anyone no the name of this siren the london fire brigade uses?

[hz6761]

"Fiamm"?

[Asphalion80]

klaxons?

[phenomanam]

just a bog standard two tone aire horn

[PULSE88]

Check The Colour Of 'Grampian Fire & Rescue' vehices based in Aberdeen City!

[wiskenc]

norfolk fire engines only have this style of siren thease days

[KieranClarke999]

Actually Oxfordshire Fire & Rescue use them to!

[hz6761]

Hong Kong have this siren, too

(But only used in late 70's to 2001)

[jamiehn123]

And Devon and Cornwall FB do to, theres one in falmouth, on an old merc!

[traintimmy]

@wiskenc And North wales

[ImRatherTall]

@wiskenc and cornwall with thier old merc!

[CDPDPatrolUnit]

This vehicle must be really old. I hope all emergency vehicles in Britain use this siren again. They shouldn't use the American wail, yelp and pier.

[fanoseagrave]

What's your opinion of the Federal Q mechanical siren as far as using it on British fire apparatus? I'm curious.

[55cifi]

I won't mind having a Q on my response car, although I'd stick with Two Tones on fire engines.

[fanoseagrave]

Here you go. Watch the video, "Command and Support." This video shows a Q will work, with proper modifications, to a car or a light-duty truck. You need two batteries, a 275-300 amp alternator, and heavy-duty cables to take the Q. But beleive me it's worth the investment once you see passersby covering their ears!!!

[fanoseagrave]

Also watch "Federal Q-1b." The guy is operating the Q from a small car. Although it's weak for a Q due to the limited power supply it's still plenty loud.

[55cifi]

I have wired three Q's up to trucks in the UK in the past, but never had one myself, look at my video titled "Mersey Fire + Rescue service on a blue light run C Two Tones" of course my recorder dosen't pick the sound up at all, so you can imagine people covering their ears with them. Which video is the one you mention?

[55cifi]

Got it, thats a pretty good sound, dosen't suit the SUV, but sounds sweet

[fanoseagrave]

You HAVE to get video of the Q's being used on those rigs!!! And to make sure the video gets a ton of hits, put the make of the truck, fire engine, Federal Q siren, and Great Britian into the tags. But that's something I GOT to see!!!

[55cifi]

I would do, but this was over 30 years ago ! ! !

[fanoseagrave]

WOW!! THAT long ago??

[55cifi]

Yes, long time, thats the only time I've everr heard a real one, a beautiful roar and growl. Nothing beats them for a firetruck sound except two tones in Britain

[fikle]

haha now that is soooo coool

[bruno666666]

cool....i dont understand the explanations but i think i got it from this video

[mattmgmhs]

Pitch changes when the waves hit your ear drum at a different rate. If you are in the ocean or a wave pool, and you run towards the ocean lets say you get hit by a wave 10 times per minute. If your already in the ocean running out. You may only get hit 3 times a minute. When the engine in the clip is moving away, you get a lower frequency for the same reason. I hope that helped.

[C20rules]

The doppler can also be used to calculate the speed of the sound sorce if you measure the pitch change.

The accurancy is depending of how accurate the speed of sound is known - wich is mostly affected by the air temperature (at normal altitudes). The accurancy in speed measurements is affected by about 1% per (6°C, 11°F) change in temperature.

This truck passed by at 68 km/h (42 mph) (calculated with 10°C, 50°F air temperature)

[billybingo2006]

The Dopplar effect is how PIR detectors work and how bats navigate, they send out a high frequency sound wave and by measuring how long it takes to return from the object it has hit it knows how far that object is away.

To be very accurate bats clich thousands of times a second as they get very close to be even more accurate!

[chrisgoding]

I'm going to stick my neck out here and say that the explanation isn't quite spot on. It has nothing to do with how long something takes to return from an object it has hit - that's a transit time measurement. The doppler effect is actually the change in frequency caused by either a moving source or receiver. The fire truck is moving towards you so it sounds at a higher pitch than what happens when it is moving away from you. This is easy to detect because our ears are sensitive to pitch.

[4dndf91]

@chrisgoding that's not an accurate explanation either. This happens because sounds waves appear longer when our distance to the source of the sound increases. As the fire truck passes by sound waves are compressed thus giving the illusion of a higher pitch, and as it moves away the pitch decreases.

it's all relativity baby

[nmfd72]

Thanks for the explanation emopope

[nmfd72]

What in GOD's name is the doppler effect??

[emopope]

Its just how sound waves work, when something comes up on you then leaves you.

[Surtur]

Kinda like in cartoons when you see the guy falling he goes "aaaaaAAAAAAaaaaaa"

[kirkorka]

Screams in cartoons are only half-Doppler effects and they go "AAAAAAaaaaaa". "aaaaaAAAAAAaaaaaa" would be more suited to Tarzan passing by swinging on a vine.

[kirkorka]

Before anyone jumps: there is no such thing as "half-Doppler".

[Surtur]

I'm talkin' when you hear the guy falling and look up and he goes falling past you yelling ;)

[FreddoX1]

it's nerd math. Don't bother you communist.

[NIGHTMAREuki]

its non-american brain reality

[67genxer]

i like the sound of these sirens better than any other, it works! its what i remember. i could not find any other videos on utube with the traditional British siren!

[dmcbride601]

This was very helpful is explaining the Doppler Effect to my 5 year old. Thank you.