A Siren's Song | A Sound Education from Dynamix

A Siren's Song

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“Square in your ship's path are Sirens, crying beauty to bewitch men coasting by;
woe to the innocent who hears that sound!”

by Homer in The Odyssey

I live on a busy street. My house sits roughly between three hospitals - all with helipads and emergency rooms. That's good for me if I have a really bad day, but my poor cat thinks wolves are after her whenever someone else is having a really bad day. I'm talking about the incessant sirens going up and down my street. And they seem to be getting louder – they penetrate my windows and brick walls with even more ferocity than ever before. It turns out that I'm not imagining this, because some emergency vehicles are now employing something called "low frequency system," or LFS. I call it "Loud F*@#$%^& Siren."

In addition to the regular high yelp of a siren, you may have noticed a lower yelping sound that seems to penetrate your car and go straight through your chest. That emergency vehicle has a secondary siren system that emits powerful omnidirectional bass tones from about 200-400 Hz. In this range, sound is "felt" more than heard - up to 200 feet away. These frequencies can penetrate auto glass and metal, wood and brick buildings, and human flesh and bones.

The sellers of these types of sirens call them "intersection clearing" devices. They didn't make them just for fun, there is a real need for something to gets more attention. We live in a world of super-quiet cars, people with earbuds playing music loudly, pedestrians hunched over their phones while walking into fountains, and general inattentiveness. City dwellers in particular have learned to tune out the pervasive sirens that scream past them daily. There have been countless accidents, some fatal, at intersections while an emergency vehicle is on a Code 3 run. Police and fire departments are continually searching for solutions that make emergency runs efficient and safe for everybody, but it's an uphill climb.

This latest solution of using enhanced low frequency sounds is not without its controversy. Opponents complain of ever increasing noise pollution. They also bring up the lack of legislation regarding the use of LFS. For instance, many police and fire departments that are purchasing the LFS units are small towns without the traffic problems of big cities. People who live or work in cities that employ LFS sirens are subjected to particularly invasive sounds while inside a building, even on the 20th floor.

And these loud and low tones aren't just an annoyance, they can be harmful to your health. Noiseoff.org says "The intense sound caused by the [LFS] siren easily triggers an involuntary stress response commonly known as 'fight or flight.' This results in the secretion of adrenaline, with ensuing spikes in cardio-respiratory rates, muscle tension, and elevated blood pressure."

But let's not forget about the police officer or ambulance driver who is sitting on top of this thundering klaxon. At ten feet away, roughly the length of a pick-up truck, these sirens emit a powerful 123 dB-SPL. Let me put that in context for you. If you were standing at the goal line of a football field and a jetliner took off 65 yards away, you probably wouldn't notice that the jet was slightly louder than the siren because you would be screaming in agony from the pain. Makers of these LFS sirens don't recommend users subject themselves to more than ten seconds of the bone rattling sound, so they usually build in a failsafe cut-off time of the tone. But once it ends, nothing stops the operator from sounding it again and again.

Clearly, there needs to be more engagement between the public agencies and the public they're supposed to protect. An effort to educate both the protectors and the protected will only help everybody in the long run. These LFS sirens are getting the attention of people in the way, but at what cost? Will their overuse cause heart attacks, panic attacks, or deafness? If people then start to ignore these, will the police come up with something even louder? Like something that goes to 11?

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