A Rumbler siren is a type of emergency vehicle siren used primarily in the United States. 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". The Rumbler is about 10 decibels quieter than a standard emergency vehicle siren and is generally activated in eight-second bursts by depressing the horn button in a Rumbler-equipped vehicle.[2][3][4]
The Rumbler was developed by Federal Signal Corporation as an "intersection clearing device". It was initially tested by the New York Police Department in 2007.[3]
According to Noise Off, a noise pollution advocacy group, more than 100 U.S. police departments had deployed the siren by 2012, including those of: Washington, D.C.; Amarillo, Texas; Tulsa, Oklahoma; and Reading, Pennsylvania. As of 2016, the per-unit cost of the siren was between US$400 and $700 (equivalent to between US$488 and $854 in 2022).[5][3][6]
In 2015, emergency vehicles in New South Wales, Australia were outfitted with Rumbler sirens and, the following year, some ambulances in Singapore began to be equipped with the Rumbler.[7][8] According to Singapore officials, the decision to adopt the Rumbler came after seeing its efficacy in U.S. police vehicles.[7][8]
Wales Air Ambulance's response vehicles are now equipped with the rumbler siren.[9] This is the second application of such equipment in the UK, having only previously been used by another response doctor charity in Hampshire.[10]
"Rumbler" was a nominee for "People's Choice Award Word of the Year" for 2016 by the Macquarie Dictionary.[11]
New vehicles operated by the Queensland Ambulance Service are fitted with a Rumbler siren.