Coming soon, and loud

Ariel Kaminer has an article in The New York Times about the latest NYPD equipment:

Joe Bader tried setting the two tones of his invention four notes apart on the musical scale, but the result sounded like music, not a siren. Same thing when he played around with a five-note interval. But when he set the two tones apart by two octaves and gave the siren a test run outside the Florida Highway Patrol headquarters in Tallahassee, the effect was so attention-grabbing that people came streaming out of the building to see what the strange sound, with its unfamiliar vibrations, could possibly be.
Which was precisely what Mr. Bader, a vice president at the security firm Federal Signal Corporation, was going for: a siren that would make people sit up and take notice. Even people accustomed to hearing sirens all the time. Even people wearing ear buds or talking on the phone. Even people insulated from street noise by a layer of glass and steel. Even New Yorkers.
Rumblers, as Mr. Bader called his invention, achieve their striking effect with a low-frequency tone, in the range of 180 to 360 hertz (between the 33rd and the 46th key on a standard piano keyboard), which penetrates hard surfaces like car doors and windows better than a high tone does. When it is paired with the wail of a standard siren, the effect is hard to ignore; like the combination of a bagpipe’s high chanter and low drone, or perhaps like a train whistle and the caboose that moves that whistle through space.
Following the lead of some other municipalities, the New York Police Department gave the devices two limited test runs beginning in 2007. It liked what it heard, with the result that a Rumbler will be coming soon to a police car near you; perhaps one speeding right at you in a high-speed chase through traffic- and pedestrian-clogged streets. And, eventually, to about 5,000 of the department’s more than 8,000 vehicles.
Some New Yorkers have already raised concerns that the Rumbler’s low-frequency vibration could be injurious to their health. The Police Department insists that there is nothing to worry about and invited me to experience the effect for myself. But when Officer Joe Gallagher, a department spokesman, considered the fact that I am in what used to be known as “a family way”, he suggested that I not actually ride in a Rumbler-equipped squad car. “I don’t want you sitting in the back and going into childbirth,” he said. “I’m not handy with that.”
I’m not so handy with it either, so I rode in Officer Gallagher’s car while Officers Jeff Donato and Matthew Powlett of the 10th Precinct drove ahead of us, Rumbling as they went.
We zoomed up the Franklin D. Roosevelt Drive on what appeared to be the only day in recent history that it was free of traffic. When at last we did encounter at least a few other cars, the officers in the front car flipped on the Rumbler, switching among its sound effects: the wail, the yelp, the hi-lo, the fast stutter.
The Rumbler is no louder than a standard siren. In fact, it’s quieter; ten decibels lower, which translates to only half the volume. But because low-frequency sound waves penetrate cars better than those at a higher pitch, drivers experience the Rumbler as much louder than a standard siren. That’s good news for pedestrians who might prefer not to be deafened, though not necessarily for the officers in Rumbler-equipped cars. To spare the officers’ ears, the device cuts off after eight seconds.
But the officers who demonstrated it for me said they had used it in repeated intervals for longer durations. And though Federal Signal describes the Rumbler as an “intersection-clearing device”, the officers also recounted using it while zipping up long stretches of highway. “It’s like the Red Sea parting,” Captain Christopher Ikone said.
Low-frequency sound can have physical effects, like making you feel queasy. Enough, in fact, to be of interest to some weapons manufacturers, but their experiments take place at much lower frequencies and much higher amplification than the Rumbler employs. In fact, despite the siren’s name, the rumbling effect is subtle; far less than what you experience when an Escalade rolls up beside you at a stop light, tinted windows lowered, custom speakers blaring and thunder bass thumping. Hearing a Rumbler while standing on the street, I felt a slight tingle under my ribs; in Officer Gallagher’s car, I felt a gentle reverberation on the seat.
I can faithfully report that the Police Department’s newest and soon-to-be-ubiquitous emergency alert signal does not cause eyeglasses to sprout hairline cracks that branch out across the lens and hang there for one long moment before the entire thing shatters with a delicate plink, as in some Bugs Bunny cartoon. Nor does it reprogram the rhythm of your heartbeat, the way a loud song on the radio can make you completely forget what you’d been humming when you heard it. Nor does it induce premature labor in pregnant women. It may, however, have caused an innocent citizen heart palpitations.
As we zoomed back down the FDR Drive, dual-tone sirens blaring so we could see the other cars scatter, the driver of a Toyota RAV4 apparently thought he was being singled out and pulled to a complete halt, in the left lane of the highway. That’s an unwise thing to do in any case; an extremely unwise thing to do when you’ve got a police cruiser right behind you.
If the driver did sustain any coronary distress from the incident, help was nearby: a Fire Department ambulance was driving just a bit farther south. As we passed, its siren let out a few warning bleats. But they were the old variety: one tone, no tingling. Compared with the basso profundo confidence of a Rumbler, it sounded like a jealous whine.