Rumbler siren

Developed in 2007 by Federal Signal Corporation, and sounding at a low-frequency level, it is designed to be heard by motorists who may otherwise be unable to hear high-frequency sirens due to ambient noise, such as urban traffic.

The Rumbler produces a pulsating, low-frequency sound between 182 and 400 hertz,[1] and is operated in tandem with a standard, piercing high-frequency siren.

The lower frequency sound penetrates hard surfaces like glass and doors more effectively than high-frequency tones.

In addition, the siren's low-frequency thumping sound also causes noticeable vibrations to drivers and pedestrians who are near it and helps to generate attention in high-noise environments like dense urban traffic.

[11] "Rumbler" was a nominee for "People's Choice Award Word of the Year" for 2016 by the Macquarie Dictionary.