How has emergency vehicle siren technology changed since 1977?

I am trying to find proof that sirens are ineffective. The vast majority of the material I have found on Google seems to point to “a Department of Transportation study” into sirens. But this elusive study was done in 1977.

Do you think this study is still valid? :dubious:

Has the technology for siren sound changed so that they now cover a larger distance?

I know they would have optimised the technology to use less power, work for longer without needing maintenance etc. But what I am looking for is the sound specifically. If the siren sound is still basically doing the same thing, same decibels, reaching the same distance etc. then this study would still be relevant right?

Thanks to Cecil for this very informative column that almost answered my question, but not quite:

Cecil mentions signal preemption technology, which turns traffic lights red in all directions when an emergency vehicle approaches. Honolulu Hawaii had this many years ago, and in addition, there were also stationary sirens mounted on the traffic signals at certain major intersections that would sound also when an emergency vehicle approached. They seemed to be activated while the vehicle was still at least several blocks away.

Another hazard: Certain birds, that have a habit of imitating sounds they hear, learn to imitate sirens. I have heard some very credible performances from time to time.

ETA: No doubt, when self-driving cars are well-established, they will be directly preempted by emergency vehicles, or even simply by cops wishing to pull you over.

The addition of white noise (which is easier for the human either to infer direction from) to sirens was a relatively recent invention (last 20 years or so I believe)

These past few years, they’ve introduced the Rumbler. Once we get oblivious to that, I’m not sure what they’ll resort to to get our attention.

Sirens are only half the equation.

In 1977 many cars still lacked air conditioning. Instead they had open windows. And they all lacked what we’d now call effective sound proofing.

And nobody had earbuds.

And traffic was half (or less) as thick.

So even if the decibel loudness & psychoacoustic noticeability of sirens measured in isolation has improved considerably since 1977, their effectiveness in actual 2016 traffic may have declined.

My non-expert opinion is sirens are borderline useless in the modern urban environment. Which they were not back in the 1960s. I have no clue where the data point taken in 1977 sits on that continuum. But it’s definitely between those two end points.

Moved to Comments on Cecil’s Columns from GQ.

It’s gotten louder. Spent 3 days in Manhattan last spring doing tourist stuff. Volume was turned up to 11+. Painful levels within a 100 yd. or so. Combined with the traffic, construction, and destruction; getting into a park was blissful. Everyone in our group was stressed out at the end of the day. Most folks on the sidewalks were plugged into their phones. Kind of an ongoing battle: distracted populace vs. emergency vehicles.

They should just pump the alarm through the sound system in my son’s car. I actually heard his rumble from a mile away once when I was outside last fall. We regularly hear (feel) him from inside the house slowing down to pull into our driveway.

There was actually talk of doing just this. Drivers with windows up, air conditioning, and the radio blasting away can no longer hear sirens. Having the ability to pump the alarm through the radio would make sure people know an emergency vehicle is coming. However, it wouldn’t tell them which direction.

I wonder with the event of the smart phone car integration if the location and direction of the ambulance can be displayed on the screen (as well as with an alert tone). This way, I know which way I need to go to get out of the way.

Personally, I’m not concerned at first where an emergency vehicle is. Once I know it is about, I’ll find it. It’s knowing it is around that is the important step.

NFPA 1901 (2016 edition) Standard For Automotive Fire Apparatus has about five pages on Optical Warning Devices but as far as Audible Waring Devices, there are 5 individual entries.

13.9.1 Audible warning equipment in the form of at least one automotive traffic horn and one electric or electronic siren shall be provided. The siren manufacturer shall certify the siren as meeting the requirements of SAE J1849 Emergency Vehicle Sirens long winded statement about access of controls for sirens from drivers area.

13.9.2 Air horns, electric and electronic sirens shall be mounted as low as as far forward as practical on emergency apparatus.

13.9.3 Audible warning equipment shall be mounted on the roof of emergency apparatus.
I suppose SEA J1849 may reference some studies but as far as NFPA, not a whole lot there.
Living on the only main road dead center between the hospital and the fire station means I am constantly bombarded by sirens and they really don’t even bother me anymore. The house shaking as the pumpers roll by and those damn air horns, now those still and most likely will always drive me bonkers.