American Reacts to Why European Sirens Are PROVEN To Be Better 

He forgot to mention that the 80 year old with his walking stick, could walk to the Hospital faster than a New York Ambulance

What I also love in European sirens is that in most countries the siren melody is ALSO different depending on WHICH emergency service it is that's trying to get through the traffic, so the ambulances sound different from the firefighters sound different from the police

Another Advantage is the Doppler-Effect. When the Sirens drive in your direction the Frequency gets higher when the Ambulance is driving away from you the frequency gets lower. With distinct frequencies (450Hz, 600Hz) you can hear the difference when it is 400Hz or 500Hz instead of 450Hz. The Us Sirence continously change there Frequency so it is harder to hear the difference.

In my understanding, it is more difficult to tell if the American siren is moving towards you or away from you, because the changing frequency hides the Doppler-Effect. Doppler Effect: When a sound source is moving towards an observer, the speed of the source relative to the observer is added to the speed of sound, resulting in an apparent decrease in the wavelength of the sound waves (they are "pushed together"). This decrease in wavelength leads to an increase in frequency, resulting in a higher pitch. Same goes for an object moving away from the observer: The sound waves get pulled apart and result in a lower pitch. So, if you notice the pitch getting higher, you know that the source is getting closer to you. This does not work if the siren changes it's frequency on it's own. Another reason is the lower frequency in general (as mentioned in the video). Lower frequencies with longer wavelengths are less likey to bounce off of objects. Therefore, the sound of a low pitched siren is more likely to reach you directly without many "bounces", than a higher pitched one. It is thus easier to tell where the siren is relative to you. It's just basic physics kiddos

Fun fact: the 2 tone siren (called Martin's Horn) in Germany even has 2 different modes. A in-town and a country-side mode, which can have a different pitch. With the direction recognition I'm not so sure. This depends much on the surrounding. In city streets with tall buildings enclosing the streets it can be misleading because of echo effects. In open spaces, like the country side or motorway its somewhat easier to locate where its coming from.

I think the low frequency of European sirens came from experience with ship sirens . At sea, during fog, the ship gives a low-frequency siren about its position and can be heard for several miles . That's my association

German here who has lived in the US for a year. I strongly prefer german siren tones as they are indeed better to hear from distance and easier to locate.

I'm from The Netherlands, and I was in NYC a couple of weeks ago, and to be frank: I did find the ambulance sirens annoying. (Other than that, I had a great time, though.) They seemed to be both too loud and too high pitched, making it a whining sound.

The police, fire brigade and ambulance sirens in Germany are traditional. The first horns were built by the Martin company. They make horns and trumpets. Therefore two different horns were installed and blown alternately. All it needed was an air compressor mounted on the motor shaft. Today the sound is generated electronically. The tone sequence is a perfect fourth. I can't say which musical note. When the vehicle approaches the listener, the tone pitch is different than when the vehicle moves away. This is the Doppler shift.

They missed one key factor that is present in sirens from the UK and possibly other countries. We inject a burst of white noise. This has been proven to help with directionality. Look it up, it was part of a major study and is why it was implemented in the UK

I also find the on-off, high-low cadence of European sirens to be better at "cutting" through ambience noise. It's a kind of sound that doesn't occur in e.g. construction work, music, or a car alarm. It stands out so much that, even if you can't immediately tell where it comes from because of echo effects, you immediately recognize that there is a siren active *somewhere* even if it is very far off in a noisy city.

I knew about the improved direction feature of sirens in the UK, and I knew it was easier on the ears than the older wailing type siren, but I was very surprised to see how much further away you could hear the siren. That on its own is a great reason to change.

Generally speaking, at least here in Portugal, emergency vehicles can have 3 diferent siren cadencys, a regular, a more urgent one and an annoying one (like a buzzer sound) to really get people's atention, like when passing crossroads for example. 1:56 Actually thats a french style tone, but the principle is using an high low siren.

A thing they didn't mention is, that as you age you generally lose some of your hearing ability. Be it because you work in a loud workplace like a factory or because you listened to loud music too much. Whatever. It is usually the high frequencies you can't hear that well anymore. So making the sirens on a lower frequency ensures that this isn't so much of an issue in critical situations.

The original manufacturer of the sirens in Germany (Deutsche Signal-Instrumenten-Fabrik Max B. Martin ) originally was specialised in signal horns for hunting and cavalry, and the original cadence was probably based either on the hunting signal for "halt" (c'g') , or the very similar cavalry signal for "make way". In Germany, those sirens are still called Martinshorn after that company.

I'm from the Netherlands, and always as a police car or ambulance passes by I get goosebumps. The sounds goes from direct to a shift of going the other direction. I think it has to do with the doppler effect. Sounds real cool. 😊

As a truck driver i usually notice the flashing blue lights before i hear the sirens, but we are also trained to be observant as professional drivers so we can see things further up the road and keep a good eye in the mirrors, also the Swedish sirens are pretty cool

There was once a field test in Germany to use the Wail signal in addition to the Martin horn. The Erfurt professional fire brigade took part in this test. However, it was not pursued further.

The perceived issue with US sirens about not realizing where the sound of the sirens come from until they are directly behind you most likely results from the shorter distance that you can hear them from. E.g. Two emergency vehicles drive with the same speed. One uses the US siren and the other uses the EU siren. Then if the US siren would only be heard for the first time from about 249 ft = 76 m away while the EU siren would already be heard from about 508 ft = 155 m away. So if the emergency vehicles would drive about 100 km/hour = 62 miles/hour then you would have the following times to react till the emergency vehicle is behind you: US siren: 76 m / 100 km/h = 76 /100 m/(km/h) = 0.76 m/(m/3.6sec) = 2.736 seconds EU siren: 155 m / 100 km/h = 155/100 m/(m/3.6sec) = 5.58 seconds. So basically with the EU siren you have twice as long to hear the siren, then by hearing it getting louder to figure out where it comes from and finally to react accordingly.

UK sirens are mostly the same as US sirens. They'll sometimes have white noise on as well, which is supposed to help determine the direction the vehicle is approaching from. Being an old git, I would like to have the two tone horn sirens back, as I think (perhaps with good reason) that they were better.

The Doppler effect plays a role as well. When the sound of the siren is closing in to you the pitch is higher than the original sound. This is because the soundwaves are pushed together by the movement. This helps us to find the direction the siren comes from. As soon the vehicle has passed you the Doppler effect stretches the soundwaves, resulting in a pitch lower than the original sound. This all depends on the speed of the vehicle. The original pitch can only be heard when the vehicle doesn't move.

In Poland, as well as in the rest of Europe, such devices generate several types of signals, and the most popular ones are: wolf, dog and le-on. In many cases, there is also a "mix" option, thanks to which all modulations sound alternately. In theory, each of these signals is assigned to specific traffic situations. "Wolf" is used rather on quiet road sections, while "dog" and "le-on" effectively clear traffic on clogged streets and intersections. The oldest and most classic sound signal is "le-on" (also called "HI-LO" in English). It consists of two alternately generated tones. However, by far most often on our roads we hear the "wolf" signal. In addition, pneumatic signals are installed in ambulances and fire trucks. The intense and loud sound of the siren is also useful in traffic jams and when crossing intersections.

Only some countries use two tone sirens in Europe, two tones are not generally used any more in the UK, here's some info on it: The traditional UK siren is a two-tone “nee-naw” siren which has mostly been replaced now with American-style wail, yelp or phaser sirens. This original two-tone sound was created by two different horns operated alternately. New sirens use one speaker (or two speakers playing the same sound). These sirens typically operate between 1kHz and 3kHz as this is where our ears are the most sensitive. I.e. the siren doesn’t have to have so much power to make itself heard because our ears hear sounds in that frequency better. If you play middle A on a piano (the one above middle C), then go an octave above that, that’s almost 1kHz. 3kHz is another octave and a half above there. Our ears have trouble figuring out where sounds are coming from that are in the 2-4kHz range. Different types of siren sound are useful in different applications. The generic siren wail (a slow rise and fall of the pitch) is very easy for people to hear from a long way away, but it’s hard for people to know which direction it’s coming from. Police will move to yelp or phaser with faster oscillation or use an electronic digital buzz sound containing many more frequencies which is more easy to locate. Uk sirens sound very different from US ones.

Also with high low you easily recognize if it travels towards you or away from you bc of the Doppler effect: if the siren (car) comes towards you, the pitch is a bit higher, if it goes away it is lower. It is very easy to spot the difference Attention: adjust volume first! It is loud! ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-imoxDcn2Sgo.html

The Netherlands used to have a different siren for police, firefighting vehicles and ambulances, making them easier to differentiate (the ambulance cadence was particularly memorable; being remembered -locally at least- as "hij is al dood" -he's already dead- in tune with the cadence) Although nowadays Dutch emergency services all use a shared 375-500Hz cadence, having their volume increased from 100dB to 110dB. This not only improved audibility, it also eliminates road users to prioritize one emergency service over another (for example; people might decide not to move over for police whilst deciding otherwise for fire/rescue)...

1) European sirens have "gray noise" 2) We have those "emergency lines" No matter where, you make a line for them. In the Czech Republic we are still learning that, but these is people agreed way to do it. And we have both. One for just running and one when you need to get through.

To understand low frequency go far is easy if you think to a ship horn, is very low cause you want to be ear very far away. Naw, with the doppler effect you can determine if a sound is moving toward you or far from you cause the sound change the pitch of a semitone, so with the european sirens can help cause we have two distinct note, the USA one have not, is insteed a continuum from hight to low and reverse. But for sure the surrounding is a major factor for directions. Then you have also some psycologic study that help to understand the reaction of the ppl to particolar motive or sound. Here in Italy (Like in other EU country) we have many different sound, but the must use are thise two; Hi-low for police (poo pii poo pii) and a modified version of HI-Low for ambulance and Fire D. That sound somethink like Poooo-pipopi- poooo etc-

I am from Estonia and I have heared sirens from 500m away and even then, all the windows were closed.

In Sweden, fire trucks have the loudest sirens, then police and finally, unfortunately, the ambulance. Standard is two-tone siren going into the trill when vehicle is going into a crossing. We do have the bull horn sound of US fire trucks but they're rarely used. The traditional wailing is not a sound used in Sweden. Fire trucks have air horns while police and ambulance have electronic sirens. Another interesting thing is that signal trucks give when backing up - the beep-beep-beep... Turns out that sound is NOT good. It should be white noise. Reson? You can't hear where the sound comes from (direction) with the beeping, but it's easier with the white noise.

Thankyou Ian, great content and very interesting and great science about sound waves😉👍👌

Very interesting! We use the European type siren in Finland. The difference was really unexpected, as you said. Also, the changing pitch catches one's attention better than a single pitch, in my opinion. And yes, the lower pitch is not as irritating as the U.S. one, and it is true that you can hear from which direction it comes relatively well.

As a Dutch person, I know the two-, or even three-tone sirens that our ambulances used to have, very well, When you're inside a car, however, they are hard to hear, often you only notice them when the vehicle is very close, and that's with no music on. Outside, they are easily heard and indeed annoying. I have often been to Belgium where wailer/howler type sirens (sometimes "wobbly") are in use (and of course I know that the UK uses them too). And they sound nicer to me, while still being loud enough.

Being a musician, a trained first responder in fire and medical emergency and working in law enforcement in Europe, I have a bit of knoledge (not an expert) in the subject. There is no perfect or universal siren. In most of Europe, vehicles are equiped with a kind of electronic "sound box", that allows you to choose from different sounds and cadences. Some are good for open roads, others for urban use, some for crossroads, others for heavy traffic. Usually, there's also one to really be as annoying as possible (yes, the idea is to force people out of the way), and never underestimate the power of a good old fashioned honk. Makes it personal, like "yes, YOU, get out of the way", and a pneumatic honk is very good in those situations. The main difference I hear in the USA (been in 8 different states, so I've heard differences between places) and in Europe (also been in different countries, and heard different sounds and ways of using them) is that in the USA, in a certain region there is a tendency for the use of a single, universal siren. In my country (Portugal), in a one minute time lapse, the emergency vehicle may deploy 3, 4, 5 or more different sounds and cadences, depending on what the operator understands as the best option. That's the main difference, for me. We use, in the same vehicle, different sirens for different purposes, at least in most of Europe. In the USA, usually (not always), it´s just one or two universal sirens. But, like I said in the beginning, there is no perfect or universal siren. That's why we use several, in the same vehicle. And modern electronic makes it easy and cheap, so no excuses. Sorry for the long text, hope it is useful.

It is proven that a typical alarm signal can not be located. So they should be an alternating signal as some places have. So an alarm signal that tells you: get on the side. Alternated with another you can locate. A fast signal has a high alarm rate but is difficult to hear where it comes from. So they slowed it down.

A big city has a lot of noises, sounds of motors, horns from cars in different pitches, light rail noises, acoustic signals from traffic lights, construction work and so on. The pattern of the high low sirens is a signal that is different from any car horn or technical noise and is always recognizable.

To understand why you have so much more difficulty with the US style sirens in locating where the sound is coming from you need to understand the physics behind triangulation. Our brains work out the direction of the sound by detecting minute differences in time of a soundwave arriving in one verses the other ear. The issue with the US sirens is that there is no discernable sound impulse to make this run-time calculation with. EU sirens on the other hand have a very clear start and stop of the soundwave when they switch between low and high frequency. It is that switching that allows the brain to work out where the sound is coming from. (Btw the way our earlobes are formed helps to detect the sound origin in 3D space). The US sirens are comparable to using single lens (monocular) telescopes in an attempt to measure distance - it just doesn't work. The Doppler effect has very litle to do with the ability to detect the origin of the sound, it comes into play when a sound source is travelling with a speed relative to your speed and passes you. When coming towards you the pitch appears higher as the sound waves are 'compressed' and when the source if moving away from you they are 'stretched' and thus ound of lower frequency.

Most importantly: You can use the expression "blues and twos" in Europe.

Love the Dutch sirens, you can hear by the sequence what emergency service is coming. Two tones - fire trucks, 3 tones - police and 4 tones - ambulances

Hey, that was really interesting, even to me as a German, because I didn't know the background and the science behind this and it was short but informative without overwhelming my attention span. Thank you and good reaction! 😀

Most important thing for a siren is to be heard from far and to be locatet easy in witch direction is it moving. So you can prepare yourself to move out of the way or just carry on, because you drive in the oposite direction of the siren.

In Jersey (the one in the UK) we have a siren that is more akin to the US siren, and as you say, when I'm in my car and I hear the siren I have no idea which direction it is coming from until the emergency vehicle is almost upon me.

oh this is great! I myself has wondered why it's better. I've heard the same thing of it being better but never known why. Great vid!

Not hearing whether a siren vehicle is approaching or driving away is a key feature. Without you would only hear that something is happening but not whether you may need to make space for them

In France police and fire fighter have two différents three tons sirens. It is mandatory to left them pass. Paramedic and some emergency véhicules (gaz emergency for exemple) have a two tons siren with a slower pitch. I have to facilitateur to pass if possible.

You gotta love how he's not even pretending to laugh after the third bad joke from Half as Interesting

He forgot one thing: The Doppler Effect. Using only 2 frequencies for the siren you can easily hear whether the ambulance/fire truck/police car comes towards you (higher pitch) or moves away from you (lower pitch). Every school kid can tell you just by listening whether it's approaching you at speed or moving away from you. As the frequencies are distinct and at relative low frequency the ear detects this perfectly.

There's another thing he didn't mention. With lower frequencies we have a better recognition of direction than with really high frequencies.

Something that may be of interest are the blue and red emergency beacons. Red light is easier to see during the day and blue light is easier to see at night.

when I'm driving usually i cant see the ambulance but i already can ear it and know more or less where it will come from.

Many UK emergency services now include white noise in the siren operation as this cuts through other noises and aids in the directional recognition. Also switching between wailing, fast siren, and two tone, helps too.

I remember that the UK tried a siren with a short white noise burst for a while, as the white noise was easier to detect directionally over a normal sound. But isn't used anymore.

That was really interesting, thanks 🙂....and you have a really nice voice too 👌

A siren has 3 functions to perform. 1: To be heard. So it needs to be loud. 2: enable those hearing it to work out what direction is it coming from. 3: enable those hearing it to work out it is getting closer or moving further away. If you hear a siren and can tell it is behind you and getting closer, get out the way, they are behind you. If you hear a siren and can tell it in front of you, and it is moving away, well, No action needed. I think the classic USA siren is based on a fan type siren, that was foot operated by the driver of the emergency vehicle. Is rises and falls pitch as it spins up and down. (the principle a Carter Air Raid siren used in then U.K. during WWII.) U.K. simply used two different pitched horns, and switched between them. There was a test in the U.K. of a siren nicknamed ‘Quack-Quack-SHOOOSH’ which gave two loud blasts (the Quacks) for the Doppler effect to allow people identify if it was approaching or receding, and to actually hear it. followed by a burst of white noise. Apparently white noise being multi spectrum makes it easy(er) to work out where the noise is coming from.

I don't think the US sirens these days can be described as only a long wail. They often start up that way, but then quickly go into a choppier / quicker siren, sometimes alternating, and then often when approaching intersections the officer or trooper will add in some other electronic sounds to get motorist attention when it is needed.

6:12 "... not as in your face...." Me, from Germany: "OK than why did I literally became deaf when the ambulance came trought the street 3 days ago?"

The German Sirene called Martinshorn. Invented in Germany in the 1930 th. Its typical Sirene in Germany and other countrys in Europe.

One thing not mentioned is that our brains react mostly to change. The wail attracts less attention (and our brain may ignore for longer) than the sudden change of pitch.

Here at Central Europe it gives differences between: • Police Vehicles • Fire Brigade Vehicles (former Police Fire Squadrons) • Emergency Rescue Vehicles (most of them organized by Fire Departments) • Postal Services (Postal Stage Coaches or Postal Bus Services) In the past at Germany, public postal passenger transports used the three tone horn signal by departuring and arriving to station stops, it had a sound like a manual blown postal horn. At Austria or Switzerland the postal three tone horn signal is still in use today, like at germany in the past, too. The former GDR police, rescue and fire brigades used different types of emergency horn signals to the western german standards, so the firebrigades often used mechanical ringing bells and like air raid sirenes sounding sirenes. Modern western german fire brigades are using two different louder martin's horns the more quiter one by low traffic, the more louder one by higher traffic at road crossings or when stupid car drivers should clear the roads immedietly.

Here in The Netherlands the sirens of the police, ambulance and firetrucks have their unique tonal composition, and the three tonal compositions are the same though the whole of the country. So you can hear by the siren what type of vehicle is comming.

I get it that he is talking from a "Average European Siren" but we are not a country, what is true for France might or might not be true for the Netherlands. Speaking of the Netherlands... It used to be the case that Police and Firebrigade had a two tone sirene. Both with their own distinct pattern, the ambulances had a 3 tone Siren (generally called the "Hij is te laat" or " He is to late" siren. You could not only hear where, but more important what was aproaching. Their dB was 100. Since 2020 I think, all services have the same two tone with a low tone of 375Hz and a high tone of 500Hz at 110dB

As I had the "pleasure" to sit in traffic with the sirens and blue lights on "my" car going, I wished, we had the possibility to switch between sounds. (And, by the way, I wish we were allowed to mount more lights on emergency vehicles.) And the "minimum loudness" of German sirens is so low, that you even can switch them off. In my semi, with the radio off and the window on the driver side one or two inches open, I do not hear them until they are to close for me to react. Only Fire and Rescue, which often have air horns as a siren, are easily heard. If they use them, that is.

In the UK, people talk about “the blues and twos”, because emergency vehicles only strobe blue lights, not red. And that’s regardless of which emergency service.

In Norway the sirene wail identivy what kind of emergency vehicle is coming. Police and ambulance scream "NY wail", fire brigade sirene make the two-tone sirene.

Fun fact regarding frequencies. US used large ELF antenna (ultra low frequency) burried in ground to communicate submarines without them needing to go to the surface. The capacity of this communication is very low, so it is okay to transmit short codes rather than fancy stories, but the principle is the same. Low frequency = higher range + capability to move thru different medias.

He forgot the most important feature of the European siren, you can detect if a siren is coming towards or away from you.

Most of the modern made emergency vehicles are equiped with variable siren options and settings so ems can choose the patern depending on the circumstances.

In addition, the emergency lights inside the EU are normed, to be seen without blinding the traffic. Usually even the number of lights, reflections angles, heigths, directions and so on are regulated. Compare that to police cars (unmarked or marked, but especially the unmarked) in the US of the A. They seem to be outfitted with LEDs by a three year old; using the cheapest available ones which are extreme bright but blind everybody. Cheers out of the old world of 🇪🇺/🇩🇪 EU/Germany and keep rockin you reacter hehe - may be sometime will see a self produced one here, Pepe

Fun fact: After opening the iron curtain, some of the easter countries in Europe began to use siren signals like US/CDN. Russia and Ukraine as well. There are a lot of different "sound patterns" across Europe.

7:40 I as a 30 year old European living 1 km away from the hospital, can hear the ambulances around there from home.

Just to get it right for the future: Martin Horn are two tone air horn produced by the firm with the same name. An other European company Fiamm also produces two tone air horns. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Bb__ON5Vqfc.html

You can clearly tell if the sound move towards you or move away from you. It is a distinctive difference. Also emergency vehicles are also often use different signals, one as they are moving on a straight road and then change it to more intensive when they move through the crossroads, mostly when they take a turn on it, to get more attention to what they are doing.

the two tone / multi cadance also has the advantage the it doesn't result in diminished response or habituation where the continuous wail siren just becomes background noise and may result in a form of selective hearing

I'm living across from a hospital in the Netherlands and therefor often hear sirens, yet I never considered it overly disturbing.

prior to the 19 60s uk emergency vehicles used bells, rapid bells but they could not be heard due t modern soundproofing

Can't say for the rest of Europe, but in Romania we have different sirens for police, fire trucks and ambulances. So when you hear it you can immediately tell which emergency vehicle it is. All of them are in this high-low style but they have different pitch and the alternating frequency differs.

The sirens here in Sweden, when you hear the sirens you can judge roughly how far away they are and in what direction. They fill their function perfectly in that regard.

Depends on the spread of the actual siren / how many sides of the vehicle you are broadcasting. Most in Europe broadcast from 1 siren, hence why you can tell where the vehicle is coming from.

as a Kid in the Netherlands, we also equated the sirens to words: "Ga Aan"De Kant" Go out of the Way "Er is"een Brand" There is a Fire "Ko~Men"Er Aan" We are on our Way "Wij Zijn"Al Daar" We are Already There With the Occasional: "Pas Op" Repeat Watch Out

in the video, it only mentioned the high low siren, but there are more differences in the high low siren itself. there are electronic and airhorn sirens, airhorn is way more "aggressive" than electric ones

European sirens are experimentally trying brief “hiss” noises interrupting the normal flow….apparently the normal siren attracts attention, but leaves people unsure about direction. The hiss is very ‘directional” in quality. Also being used for a revering (backing-up) warning

There is IHMO a much more important factor in making emergency vehicles less annoying: By not using the siren all the time. At least here in Austria emergency "in action" only need to use their red and blue lights - from that alone everybody is required to give them the priority. The usually only switch on the siren if they are about to do something that's against normal traffic rules - like driving through a red light, or driving on the tram tracks. Especially at night the lights alone are enough to make them very well visible, so they might not use the siren at all then.

Emergency vehicles i Sweden use both the high/low and the wail/yelp depending on the situation and surroundings. But in most high speed situations the high/low is used because it travels very far.

The UK emergency services have been experimenting with introducing an intermittant white noise, or a "SHHHHH" sound, as this supposedly helps in determining the direction the siren is approaching you from.

On a related note, I have noticed that US emergency vehicles use lights and sirens all the time, with out regard for the traffic conditions. I once stayed in a hotel across the road from a fire station in Philadelphia and those trucks left it was with the sirens going all three times, even at 3am - there was no traffic of any kind and they had traffic lights to stop any traffic, if there had been any. Why? I have seen the same on freeways, their lane is clear - because it’s 5am - but they still have the siren on. That doesn’t happen here, in the UK, lights always but siren only when needed. Not sure about other areas but where I live they seem to have 3 sirens - the US style one, trad 2 tone and white noise - but mostly use the US wailing one.

if there is low traffic during the night they will turn the sirens off in switzerland because its only needed if people are supposed to give way.

I call that blindness by sound. Too loud = unable to determine location

They didnt mention the most important part: no matter if You are in a car or if the sound bounces and You are not sure where the siren is coming from - with two tone siren You can always be 100% sure if the siren is getting closer, moving away or moving paralel to You. Doppler effect is very clear on not modulated flat tones.

The Europen sirens usually huse a horn wich has a more foreward sound distribution, this means the sound of the siren is more foreward directed.

The color of the sirens is also defined. In Germany only for rescue cars (ambulance /police/ fire trucks/ catastrophic disaster units) the blue color is allowed. No other one is allowed to use the blue color. So if you see a blue color flashing light on the street, you are aware.

And when you get one with a white noise generator, you can instantly tell where it is in relation to your direction of travel.

Lots of Wee-Woo and lights flashing in the US. More often is not more effective. Applies also to annual work time.

I am a Paramedic in Europe and have been traveling a lot during my time on the Job. From 2011 to 2014 I assisted in repatriating wounded or sick travelers and vacationers from their holiday places worldwide. I often hear our lokal Sirens from almost a Kilometer away when I walk to the stores or sit on my balcony, but during my Trips to the USA, Brasil, Thailand and Egypt I almost never heard a Siren up to the point when the respective Emergency Vehicle was almost upon me. Another practical thing of the European System is, that one can tell the differrence wether the Vehicle approaches you or is going away from you by the slight difference in the pitch.

The advantage of two single notes over a whaling siren is that you can hear if the siren is approaching or departing by the pitch shift caused by the doppler effect. The frequency of a siren moving away will drop while the approaching one will get higher in pitch.

ye i can tell you from experience as someone who lives in a place in a valley between mountains every time i hear a siren i know witch dirrection its coming from even when they are going down the mountain

Another study, some time ago, showed that interspersing white noise bursts in the sirens were beneficial. White Noise is a multi frequency sound which does not need to be so loud, but had the best directional recognition. The normal siren sounds were still needed to grab attention though. Nowaday, many 'vehicle reversing' warnings seem to use white noise bursts, probably because they can be quieter.

This made me think of when I was learning to drive a car. I drove up next to a firetruck parked on the sidewalk, which at the same time turned on its sirens. I stood on the breaks and nearly soiled myself.

I was just on vacation in California visiting from Finland and every time I heard sirens I just felt completely confused as to where the sound was coming from. Never had that experience with sirens in Europe.

I live in Norway and my house is approximately 2 kilometers away from the nearest highway, and I can hear the siren and it’s super easy to distinguish what it is (police, ambulance or firetruck).

The difference is that people in the UK recognise the emergency sirens as a good thing, in the USA a siren forces people to run away from a so called emergency vehicles for fear of getting shot.

I couldn't find if someone already wrote that in another comment. I live in Germany. We have an unscientific name that goes back to the inventor: "Martinhorn". We use the alternating tone horn, in earlier times it was a set of compressed air horns, today it is mainly generated electronically. Compressed air horns today often only on the large fire engines. The pitch of different horns may differ, but must be between 360 Hz (approx. F#) and 630 Hz (approx. D#). The tone interval must be a perfect fourth (e.g.: a′ and d″). In Germany there is also a switchover for urban and rural environments. Due to the physical principles of sound wave propagation, the city operating mode uses higher frequencies, which then radiate more in all directions around the emergency vehicle in the case of electronic special signal systems, while the country operating mode uses lower frequencies, which in the case of electronic special signal systems are then radiated more forward in the direction of travel. Due to the higher frequencies of the city circuit, the special signal can then be located better for road users than a lower-frequency signal, even if there are reflections on buildings. The special signal systems from different manufacturers can sound a little different, but they all have to adhere to the tone interval of a fourth described above. In my opinion, the best sound is no longer produced by Hella systems, but by Hänsch, e.g. the special signaling system type 624.