Electronic Sirens – A discussion.

Electronic Sirens on Emergency Vehicles
ANOTHER “FAILED EXPERIMENT” FROM THE SIXTIES?
By
Kevin O’Connell

Are you still wearing corduroy bell bottoms? Nehru jackets? Beatle boots? Shag haircuts? Paisley shirts? Ben Franklin sunglasses?

Do you still refer to a raincoat and wading boots as turnouts? Do people still ride your tailboards with impunity?

Listening to “Boss Hits” on your 4 track? Driving a “really groovy” VW bus with tie-dyed curtains?

Hopefully your answers to these questions are all emphatically negative. Thankfully many of you are too young to remember the embarrassing things people did twenty five to thirty years ago (as if you could care – you’re too busy tattooing and piercing yourselves so you’ll have something to be embarrassed about in the future).

Why then, do many agencies still cling to another bad idea from the sixties; the electronic siren? After all, they seem to do a better job of instilling false confidence than actually warning other drivers. The answers and excuses I’ve heard over the years are numerous and nearly always rooted in myth or ignorance. In the interest of brevity, let’s just debunk the three most common notions:

Myth #1 – Electro-Mechanical sirens are too loud.

Probably the most illogical and emotionally-charged claim offered by opponents of real sirens. People who make this claim usually have to depend very heavily on their air horns to break intersections. They base their stance on the notion that real sirens are the primary cause of hearing loss among firefighters.

FACT: The biggest threat to your hearing comes from simply riding on your apparatus. For nearly fifty years the fire service has embraced cab-forward designed apparatus in which the entire crew becomes intimate with a large, high-powered noise generator; the engine. This is especially true of the poor slobs who ride in the jump seats. Why? Because this is a continuous noise. Unless you’re staged at a large campaign fire, chances are you’ll be exposed to this hazard most of the time in the apparatus.

Here’s how it works: Large engines with their heavy rotating and reciprocating masses set-up a low frequency harmonic effect of substantial amplitude. This type of noise doesn’t need your ears. It is conducted through the bone around your ears. Instead of the eardrum gently working the malleus (hammer) in your middle ear, all of the middle ear is overwhelmed. It’s not hard to imagine the devastating effect that long-term exposure could have. As a staunch advocate of communications headsets, it pains me to admit that headsets and hearing protectors do precious little to protect against low frequency harmonic effect, and in some cases, can actually exacerbate it. Some protection can be provided by a thorough application of sound barrier insulation. On the bright side, the fire service has finally accepted tilt-cab designed apparatus, which significantly reduces engine noise by eliminating the need for an engine cover with large openings. Considering the many significant advantages of tilt-cab apparatus, it’s disgraceful that it took something like axle weight laws to strike a blow for progress.

By the way; headsets and hearing protectors provide excellent protection against the sound generated by sirens. Some people are so anal about siren noise that they take things to ludicrous extremes.

I once had a fairly well-respected battalion chief tell me that he had succeeded in eliminating real sirens from his department’s front-line units. He went on to brag about how he had reduced electronic siren noise in his cabs by building insulated plywood boxes around the speakers. I was astonished. This guy didn’t have a clue! His department had locked into one brand of apparatus and let the salesman spec the warning devices.

The manufacturer had mounted light bar speakers with a horn opening of 5″ x 8″ behind the bumpers with openings of 3″ x 4″. It doesn’t take a genius to realize that this arrangement forced a great deal of speaker output to be deflected back under the cab, making almost as much noise in the cab as in front of the vehicle.

More importantly, actual sound output to the front of the vehicle was compromised to the point of being nearly ineffective. When I diplomatically explained these things to the chief, his response was tantamount to “Don’t confuse me with logic, reason and facts. My mind is made-up!”

Electro-mechanical sirens don’t continuously operate at full volume. Electronic sirens do. Comparisons of time-weighted average (or TWA, a favorite OSHA term) noise levels during emergency responses usually come-out fairly even, with real sirens faring better, especially on long runs.

Myth #2 – Electro-Mechanical sirens use too much current.

Like the arguments used against electric driveline retarders, this claim is based on the gristle-brained notion that simply bolting a real siren on your rig will automatically add a continuous 100 amp load to your electrical system, killing the batteries and wreaking havoc with sensitive electronics and communications equipment.

FACT: Real sirens only draw current during wind-up and full wail. Electronic sirens draw current continuously while activated, albeit at a lower rate. That lower rate is misleading; It has been estimated that six to eight electronic sirens would be needed to do the work of one real siren.

The real battery killer is the operator who leaves his vehicle idling for extended periods of time while lit-up like the Las Vegas Strip. Every 50 watt halogen lamp you put on your vehicle adds about 4.2 amps of load while lighted. The continuous siren load myth is often invoked by people trying to justify the use of large alternators and/or battery arrangements. While I advocate using six-pack battery arrangements and large alternators, I cannot condone misleading people about imaginary electrical burdens.

A few years ago, while touring the repair facility of a large fire department on the southern coast of California, I noticed a lot of holes on apparatus where real sirens had obviously once been mounted. When queried, the shop foreman (a good friend) told me that his department had decided to remove their real sirens to reduce battery failures. I asked, Truthfully now, have you noticed any difference?” He sheepishly grinned and said “No, not really”. Within a year real sirens began to mysteriously reappear on the rigs.

When it comes to load-induced battery failures, it is important to remember this: 1) Alternators are intended to sustain loads. They are not battery chargers. 2) No matter how large, alternators do not produce full current capacity at idle.

Incidentally, load managers are becoming increasingly popular on fire apparatus. These devices are a great innovation. They sequentially switch lighting loads on and off minimizing voltage spikes. When battery voltage begins to drop, loads are sequentially shed until voltage stabilizes. Additionally, some private ambulance operators are enjoying success with isolated siren battery circuits.

The most popular real siren draws 105-125 amps at full wail, a momentary load imposed only a fraction of the time during a response. A Los Angeles manufacturer guarantees their real sirens will draw 70 amps or less at full wail, which is less than the continuous load of many emergency warning light systems.

A very heavy 25% cycle during a response would average 17 1/2 amps continuous load. (Kind of makes your 55 amp air conditioner seem pretty decadent, doesn’t it?)

Moderate in-rush current of a flashbulb’s duration seems to be an electrical evil spirit to intellectually-challenged critics, who consistently fail to realize that there is an equally brief voltage spike (more dangerous than voltage drop) upon de-energizing. These are traits common to electrical loads. If a real siren is a villain, then your vehicle’s starter is a mass murderer!

Myth #3 – They cost too much!

A real siren will typically add $1,500 to $2,000 to the cost of a new fire apparatus. This is offset several times over the life of the rig by never having to listen to an airhead, finger in nose, saying “I never heard the siren! I’m suing!” (My personal favorite – “Why do you have flashing white lights on your roof? What do they mean?” The correct answer – “They don’t mean anything. The salesman told me to buy them”.)

Actually, it doesn’t take an airhead. Nearly everyone has a personal horror story about a near disaster involving an anemic peanut whistle. My wife came close to being creamed on several occasions in the city where she works. Another agency that bought what the salesman told them to. Their “Chevy Corvair” pumpers (rear engine, insufficient front axle weight) were equipped with siren speakers which weren’t even approved for use in our state! If those twits had hurt my wife, I’d own that city today.

Let’s face it – most traffic collisions involving emergency responses bring-out litigious land sharks. And they usually have a case.

My own chief chastised me a few years ago for outfitting a new rescue squad with a real siren. I backed it up with a dual amplified electronic, each amp driving a 200 watt speaker.

The siren and two speakers were mounted out front on a push bumper for maximum effect. “That thing has too much siren!” the chief complained. “Take all of that crap off. It looks too aggressive. We didn’t do it that way in (his former agency)”.

It was all I could do to keep a straight face. At that moment his former employer had two engines out of service for “I never heard the siren” collision repairs! That chief is long gone, “all that crap” is still there, and the vehicle in question has never been involved in a response-related accident.

The seemingly high initial cost of a real siren is misleading. Unless you specify a siren, most manufacturers will use a cheap throw-away box. As many people have reminded me, the life expectancy of an electronic siren is a fraction of that of a real siren.

Besides the cost of numerous replacement boxes and speakers over the life of the vehicle, the hidden cost of downtime and equipment changeovers to a reserve rig is substantial. That little peanut whistle wasn’t such a bargain after all, was it?

If all these arguments haven’t penetrated that cartilage between your cars, please consider this: Electronic sirens are directional, especially when used with unconventional speakers. Real sirens are omni-directional.

Electromechanical sirens work as well to the sides of the vehicle as they do to the front. While it can certainly be argued that vehicles ahead of you present a risk, they are more of an annoyance compared with an even greater hazard: Those vehicles you can’t see – and those vehicles that can’t see (or hear) you!

(Kevin O’Connell is an emergency equipment specialist and President and CEO of B&M Siren Company. His articles have appeared in many prestigious national fire engineering publications, and we think him for offering this article for publication..)