Wail v. Yelp- really make any difference?

#1
Any statistical data that demonstrates one or the other is better for one thing or another? Or no one hears either, so they are really more for the driver's benefit...
 

mcpd2025

Veteran Member
#3
I was not aware of that... it seems that drivers respond better to the yelp because it changes more. The wail is slower and it seems like people don't really react to it. As such, I keep my siren on yelp and hit the manual button for hyper yelp when I approach an intersection, crest of a hill, parking lot, etc. Changing it up seems to wake people up and make them look around a little bit. By and large though, nothing seems to really work. Lights, siren, air horn... doesn't seem to influence about 70% of the drivers in my area...
 

NCFD43

Senior Member
#5
We have audible preemtion devices on the majority of our traffic lights, so it helps out to have the siren on yelp for that. Otherwise, its a mix of wail and yelp for me, with air horn thrown in as a wake up call to some people. Ive heard some people say wail is better, and some say yelp is better, but there really is no "good" tone that works all the time. Be seen, be heard, as best as you can.
 
#6
Flashguy said:
From the driver operator book, sirens are outrun at speeds above 55mph. Longer sirens that go deeper and higher slowly will give a longer distance in front of vehicle. Quicker patterns will travel shorter distance.

Here's an interesting web page: Mechanical Sirens Frequently Asked Questions
I'm no audiologist, but my BS meter is pegged by several things stated on that site. No reflection on you of course.
 
#7
norcalbusa said:
I'm no audiologist, but my BS meter is pegged by several things stated on that site. No reflection on you of course.
It's not BS, it's sales. That page there is sponsored by a company that makes mechanical sirens, and they aren't trying to be sneaky about it. Google "timberwolf siren" and see what comes up.
 
#8
The fire department I work for is going with a multi tier approach for sirens on the new trucks... 200w electronic, Howler, Screaming Eagle and twin Grover air horns... bet people still wont move!
 
#9
I remember reading an old study that said one of them is more audible in built-up urban environments, and the other one in open, rural areas... but can't remember which was which.
 
#10
We were always taught that wail is easier for motorists to determine in which direction the sound was coming from, so it would be better for intersections. Then we were taught that changing the tones at intersections, from no specific tone to any other one, got peoples attention better. Seems to be little to no scientific research put into this. Wonder if I could get a multi million dollar grant to "research" this and publish the results. Just think of all the cool toys I could buy in the name of research. But personally, I can hear a wound out Q while sitting at an intersection than any other siren. We can also hear a Q coming thru the city long before any other siren, but once again, I have no science to back it up.
 

Zack

Senior Member
#11
Bigassfireman said:
We were always taught that wail is easier for motorists to determine in which direction the sound was coming from, so it would be better for intersections. Then we were taught that changing the tones at intersections, from no specific tone to any other one, got peoples attention better. Seems to be little to no scientific research put into this. Wonder if I could get a multi million dollar grant to "research" this and publish the results. Just think of all the cool toys I could buy in the name of research. But personally, I can hear a wound out Q while sitting at an intersection than any other siren. We can also hear a Q coming thru the city long before any other siren, but once again, I have no science to back it up.
Here is what Ive always been taught and what I teach my crews:


The Wail sound's wavelength (long) travels a far distance but is difficult for a human to determine the origin of the sound.


The Phaser sound's wavelength (very short) travels a short distance but is very easy to determine the origin.


Thus, I teach people to use Wail while on long straight-a-ways and with vehicles up ahead. About the time you'd be pulling your foot off the gas go to Yelp, and when you'd be applying the brakes go to Phaser.


As I'm actually at the line of the intersection I interject the airhorn "randomly" to further break up the noise and garner attention.


Additionally, if you are running priority with other emergency vehicles, it's best to "stagger" your tones, so if one person is using Yelp, you should use Phaser. Etc.
 

Klein

Senior Member
#14
Zack said:
Here is what Ive always been taught and what I teach my crews:


The Wail sound's wavelength (long) travels a far distance but is difficult for a human to determine the origin of the sound.


The Phaser sound's wavelength (very short) travels a short distance but is very easy to determine the origin.


Thus, I teach people to use Wail while on long straight-a-ways and with vehicles up ahead. About the time you'd be pulling your foot off the gas go to Yelp, and when you'd be applying the brakes go to Phaser.


As I'm actually at the line of the intersection I interject the airhorn "randomly" to further break up the noise and garner attention.


Additionally, if you are running priority with other emergency vehicles, it's best to "stagger" your tones, so if one person is using Yelp, you should use Phaser. Etc.
... +1 verbatim
 
#15
Here is how I've always told people to use the siren. Pretty much along the lines of what Zack said.


Wail - Empty stretches of road, whether or not there are vehicles ahead of you (more than a couple blocks)


Yelp - Approaching vehicles (One block or less)


Phaser/Piercer etc.. - When you are at the vehicles in front of you/cutting through traffic


Hi-Lo - Used for moving people only. I.E when at an event and cutting through crowds.
 

FireGuru

Senior Member
#17
ryan81986 said:
Here is how I've always told people to use the siren. Pretty much along the lines of what Zack said.


Wail - Empty stretches of road, whether or not there are vehicles ahead of you (more than a couple blocks)


Yelp - Approaching vehicles (One block or less)


Phaser/Piercer etc.. - When you are at the vehicles in front of you/cutting through traffic


Hi-Lo - Used for moving people only. I.E when at an event and cutting through crowds.
I pretty much agree with this statement. It is my own personal and professional opinion that the WAIL function of the siren works well for long distances. The cycle it produces carries for miles. It also helps get hearing impared individuals attention.


The YELP function is a tighter and faster cycle within the hearing range. This works awesome for approach to cars in front who are not responding to the WAIL function and also helps get the different cycles of frequency to penetrate the vechicle of cars that have radios on, can sneak in sound waves (frequencies) that normally would not be within a song or program.


The discussion of the other tones, including YELP, on the siren are just other TOOLS used in short bursts to get attention of motorists/pedestrians within the area that are not responding to another function(s) of the siren.


It has been my experience that PHASER can cause some confusion and cause drivers to react negatively. Short bursts seem to work great, but long bursts have created me more trouble than it was worth.


Hope this helps.
 

Flashguy

Senior Member
#18
Zack pretty well summed it up. If you haven't taken an EVOC course yet, please do. The only comment that scares me a little is about using the gas and break with your siren. Driving to your siren tends to make your driving more aggressive than needed. Remember all the basics: can't help if we don't get there, emergency vehicles "request" right-of-way and always drive with "Due Regard." if you don't, the court will eat you alive.


Be Safe!
 

chief1562

Silver Supporter
#20
NPS Ranger said:
I like this video, the driver forgets he's being filmed after about halfway and gets kind of lazy, but it illustrates this thread.


Is it just me or did they not slow down for intersections before going through them. Good thing nobody comming form the other direction was in a hurry to get through those intersections. that's typical almost drove over a drive once he finally pulled over in the same place I needed to go though never heard the siren or seen the lights and I was alternateing sounds with the horns too. accident avoided
 
#21
Zack's statements pretty well sum up recommended practices. The Mechanical siren's advantages and use of air horns rely upon the fact that multiple frequencies are produced in the warning signal, whereas traditional electronic sirens have used a "pure" tone osicillator. Newer mechanical-sounding digital electronic sirens are more effective in reproducing the effect of a mechanical, but people will respond differently because not all tones are heard by individuals. Teens have better hearing, some folks have low frequency hearing loss, yet others suffer from high frequency hearing loss. Also, there is a difference in hearing and processing noise. For example, people zone out and while the had the capacity to hear certain speech or tones, they aeren't "listening". Changing up siren tones is our effort to make them "listen".


There have been scientific studies on which the siren practices and recommendations are based. Speaker placement studies were conducted on wail and yelp using single and dual speakers, and that research was used in developing curriculum for the EVOC classes in the 1980's and later. You should not be lulled into a false sense of security by the siren - states do issue driver's licenses to the deaf and hard of hearing, but these drivers usually respond to the lights better than "normal" drivers.


Studies in Canada also showed dispatchers could understand officers radio transmissions better during wail and hi-low tones. So if you are repeatedly asking the dispatcher to repeat try backing off the yelp and hyperyelp. Note that the Powercall warble tone was not tested, but a lot of departments like to use that tone with an added mechanical siren or electronic Q and airhorns.


And if you are using two electronic sirens, don't use both sirens on the same tone at the same time. The frequencies tend to cancel out each other.
 

Zack

Senior Member
#22
The other thing to remember, is if you burry your bumper (and siren speaker) in the tail end of the car infront of you, the driver inside is going to have a very difficult time hearing you.


The best practice (for a number of reasons) is to align your siren speaker down the drivers side of the vehicle in front of you.


This allows the siren sound to be unobstructed and is easier to hear by the driver infront.


Having been a part of the exercise in EVOC where we chased each other around in trying different siren techniques, I can personally say it makes a world of difference.
 
#23
I know a few old timers who just put the siren on yelp and respond like that the entire way to the scene.
 
#25
Its all about "sound waves" and how they travel thrue the air and space i know i have seen actual scientific data somewhere but i dont remember where.
 

Zack

Senior Member
#26
norcalbusa said:
We're getting a bit off topic on an anecdotal "use" tangent. I'm looking for scientific data/study please, if anyone has it.
Okay....


A quick Google search revealed this:


Lights and Siren: A Review of Emergency Vehicle Warning Systems


The piece is from 1991 and explains emergency vehicle lights, markings and siren usage. It has a comprehensive bibliography that will point you to the respective studies.


Here is a relevant passage from the article:


The use of different siren modes (eg, wail, yelp, high-low) has been controversial. One commentator recommends different modes for different traffic conditions (50), and some studies have suggested that the high-low European-style siren is less effective than other modes (7,51). However, two informative studies showed no significant differences between various siren modes (44,52). A national consensus committee and other have recommended the high-low siren as the most appropriate emergency vehicle signal (53,54). Efforts to identify the optimal siren signal are likely to achieve only marginal improvements, given the overall limited effectiveness of audible warning devices.


The most relevant references from the piece seem to be:


Childs B: The siren. JEMS 1983;8:49-51.





Skeiber SC, Mason RL, Potter RC: Effectiveness of audible warning devices on emergency vehicles. Sound Vibration 1978;12:14-17,20-22.






Fidell S: Effectiveness of audible warning signals for emergency vehicles. Human Factors 1978;20:19-26.



Granted, these studies are 30 years old... but if the science is sound....
 
#27
Get 2 speakers and mount them on the push bumper... makes a big difference in sound.


As for wail vs yelp. What everyone has said before.. wail for long distances, yelp for short.
 
#28
norcalbusa said:
We're getting a bit off topic on an anecdotal "use" tangent. I'm looking for scientific data/study please, if anyone has it.
I knew if anyone wouldn't accept anecdotes, it would be you! I've often wondered why there isn't a more scientific approach and study on a lot of this stuff - light placements, flash patterns, sirens, traffic arrows, etc. I've never seen anything scientific - just LOTS of opinions.


I think there'd be a lot of money to be made if you could legitimately quantify safety increases based on various factors, and then do consultations with agencies to improve their fleet.


Title 13 doesn't include any explanation for why only wail and yelp are allowed in California - or what each should be used for. Do you know if there's any supporting documentation from when different sections were written in?
 

theroofable

Veteran Member
#29
norcalbusa said:
We're getting a bit off topic on an anecdotal "use" tangent. I'm looking for scientific data/study please, if anyone has it.
I think there are way too many variables for there to be a definite answer on this, even with many hours of testing and studies.
 

Zack

Senior Member
#30
RolnCode3 said:
I knew if anyone wouldn't accept anecdotes, it would be you! I've often wondered why there isn't a more scientific approach and study on a lot of this stuff - light placements, flash patterns, sirens, traffic arrows, etc. I've never seen anything scientific - just LOTS of opinions.

Check out my post a couple above yours... I linked to a study (albeit a little old) that did scientifically look at this stuff.


;)
 
#31
RolnCode3 said:
I knew if anyone wouldn't accept anecdotes, it would be you! I've often wondered why there isn't a more scientific approach and study on a lot of this stuff - light placements, flash patterns, sirens, traffic arrows, etc. I've never seen anything scientific - just LOTS of opinions.

I think there'd be a lot of money to be made if you could legitimately quantify safety increases based on various factors, and then do consultations with agencies to improve their fleet.


Title 13 doesn't include any explanation for why only wail and yelp are allowed in California - or what each should be used for. Do you know if there's any supporting documentation from when different sections were written in?
Hah! And you know my least favorite- "emergency lights on or off (ala CHP) once a stop is made and pulled off the road"?
 
#32
Zack said:
Check out my post a couple above yours... I linked to a study (albeit a little old) that did scientifically look at this stuff.

;)
Good find. It's just a literature review rather than original research, however. I'd be curious how much of the cited literature is primary source, and whether there's any actual scientifically valid experiments amongst them. Plus, as you said, it's already 20 years old, and a bunch of the cited stuff goes back to the 60's and 70's.


However, depending on the validity of the conclusion (and whether it could be defended), this statement seems to strike at the heart of NCB's original question: "Fourth, several studies clearly demonstrate that the siren is a severely limited warning device, effective only at very short ranges and very low speeds. Differences in siren mode do not appear to be important."
 

theolog

Senior Member
#33
Zack said:
Here is what Ive always been taught and what I teach my crews:


The Wail sound's wavelength (long) travels a far distance but is difficult for a human to determine the origin of the sound.


The Phaser sound's wavelength (very short) travels a short distance but is very easy to determine the origin.


Thus, I teach people to use Wail while on long straight-a-ways and with vehicles up ahead. About the time you'd be pulling your foot off the gas go to Yelp, and when you'd be applying the brakes go to Phaser.


As I'm actually at the line of the intersection I interject the airhorn "randomly" to further break up the noise and garner attention.


Additionally, if you are running priority with other emergency vehicles, it's best to "stagger" your tones, so if one person is using Yelp, you should use Phaser. Etc.
EXACTLY!!! :thumbsup:
 

BLUELIGHT

Established Member
#34
Don't know about studies, but I'm of the opinion that some wouldn't move even if the emergency vehicle was allowed to tap them lightly. People are so oblivious to their surrounding when driving, especially to the rear.
 

SomeBloke

Senior Member
#36
Sorry to resurrect this - but I found this snippet from the UK TV show "Police, Camera, Action" in the late 90s. There's actually an old London Fire Brigade, Fire engine with this "siren" fitted....I'll try and find it..

 

SomeBloke

Senior Member
#39
If I might ask a dumb question, if it can't be heard in the cab, how can motorists hear it so well?
I'd assume because it's being projected forwards, and away from the onboard person(s) of the emergency vehicle.
 
#40
Doesn’t sound great but the benefits seemed to be pretty massive. I wonder why it never caught on
Honestly, even with all the research they did, it's hard to say that it's more than anecdotal evidence of being more effective. Like when they're showing the comparison of a response with a normal siren versus theirs, even going through the same intersection at the same time of day, you're still kind of comparing apples to oranges, because the people and conditions will never be exactly the same.

And then you always have to wonder to what extent "novelty" is a factor in the effectiveness of warning equipment (both audible and visual.) When the medic talks about both teams on a soccer field stopping in their tracks and staring at the ambulance as he drove by, you have to wonder how much of that is them all thinking "What the heck is that?" and how much of that reaction will be dulled down even by the second time they hear it, "Oh, there's that weird new ambulance again..."

It's the same thing with the states that are adding green warning lights to their snow plows, green might be more "visible" by some standards, but some of the added effectiveness comes from the fact that it's novel, people are like "what the heck is that flashing green thing ahead of me in the blizzard?" Or another great example is Powercall sirens; some people swear by Powercall being the most effective siren tone ever, but how much of that is the actual audio qualities of the tone, and how much of that is that it's kind of a weird sound that's not the same as your traditional wail and yelp?

Honestly, I'm not sure what my point is other than that those of responsible for spec-ing/building/operating emergency vehicles can't get complacent. Like someone mentioned old-timers who just turn the siren onto one tone and leave it that way the whole time. We need to try new things both on individual emergency incidents, but also try new things in general over time.

...I suppose I'll get off my soapbox now.
 

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