In comparison, thunder is 120 dB, and a primary siren (measured in highly controlled circumstances about 10 feet from the siren — in steady air) is normally 119 dB.
"In a street environment where you're 20 to 30 feet away, you're actually detecting less than 119 dB," he says. "The Rumbler is about 10 dB below that, in the 109 dB range, which is just a little louder than some traffic patterns."The system
A complete Rumbler Intersection-Clearing System includes an amplifier, a timer, two subwoofers and vehicle-specific mounting hardware.
Another electronic siren, a primary (100/200-watt) siren, must be in place for the Rumbler to work. (The Rumbler cannot be used with mechanical sirens.) The system reads the output of the primary siren, duplicates it, but drops it to a lower frequency (reducing it by two octaves), and amplifies the sound through two high-output woofers. Morgan says the primary siren and Rumbler work together like a duet.
Anyone who installs other police speaker or siren systems can install the Rumbler. The speakers, a little larger than a coffee can, are installed in the wheel wells. Controls mount under the hood or in the trunk of the car.
The Rumbler was designed for installation in Crown Vics, but has been installed in SUVs as well as Chargers and Impalas. In the future, Morgan says the Rumbler will be made smaller to fit into smaller vehicles. Federal Signal is also working to reduce costs.Fleet feedback
The Metropolitan Police Department in Washington, D.C., has 79 new marked vehicles (2008 Crown Vics and 2007 Impalas) equipped with the Rumbler.
"People are hearing sirens all the time and nobody is paying attention," D.C. Fleet Manager Greg Hester says, but the Rumbler is something different that causes people to look up.
"I'm not sure that it's the noise that the people are hearing, but it's something different," he says.
As a result, he says the greatest benefit is officers are able to be identified more easily when approaching intersections.
Morgan advises officers not to run the Rumbler unnecessarily. Like anything else, people could start filtering it out. That's why the Rumbler shuts off after 8 seconds.
"If you use the Rumbler in the appropriate situations, the heavier traffic, the intersections, it has more impact," he says. "Then it becomes something truly different in the environment."
About a year ago, D.C. police tested a Rumbler system near Gallaudet University, a world leader in liberal education and career development for undergraduate students who are deaf and hard of hearing.
Police sirens previously were not heard there.
As a great concern, officers with the Rumbler say it has helped people in crosswalks identify an approaching vehicle that needs the emergency right of way, he reports.
"All new cars are going to be equipped with the Rumbler," Hester says. "That's how pleased we are."
North Reading, Massachusetts, has had the Rumbler in its police vehicles for approximately two years. The city's police department has five of its 10-car Crown Vic fleet carrying the Rumbler, and each new vehicle has the system installed — including unmarked units.
"I think it's phenomenal," says North Reading Police Department fleet manager Sgt. Tom Romeo. "If it saves one collision, every unit has just paid for itself. And that's the way I look at it."
In California, the Elk Grove Police Department had the Rumbler installed in its new Dodge Charger about six months ago.
"The most important benefit of the Rumbler is having the added safety feature when clearing intersections or rolling Code 3," says Lt. Craig Potter of the Elk Grove Police Department, who oversees the department's fleet services. "The officers love the Rumbler and wish we had it installed on all of our patrol cars."
The Elk Grove Police Department is installing the Rumbler in its vehicles, as its 64 marked-vehicle fleet is replaced with new vehicles.