Back-up beeper

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A back up beeper warns of a garbage truck backing up as it works its way around a cul-de-sac.
A white-noise back-up beeper provides a less disruptive alert than the original pure-tone alert.

A back-up beeper, also known as back-up alarm or vehicle motion alarm, is a device intended to warn passers-by of a vehicle moving in reverse. Some models produce pure tone beeps at about 1000 Hz and 97-112 decibels.[1] The back-up beeper was invented by Ed Peterson. Peterson sold the first reverse warning system to Morrison Knudsen, the engineering company based in Boise, in 1967.

He was the first to do it, and he patented it, although some others were working on systems at the same time that had bells, Mark Peterson said.

The company now sells about one million of the backup alarms annually, called the Bac-A-Larm, and is the world's largest supplier of the systems.[2]

It was first manufactured as model BA1 in 1963.[3] ISO 6165 describes "audible travel alarms", and ISO 9533 describes how to measure the performance of the alarms.[4]


Back-up beepers have been criticized by the public and in scientific literature.[1] Beepers are at or near the top of lists of complaints to government road builders about road construction noise. There is published concern that due to desensitization and the cry wolf effect people tend to disregard ever-present alarm sounds, diminishing their effectiveness.[5] The normal level of 1000 Hz pure tone beeps at 97-112 decibels, considerably higher than the long-term hearing loss limit of 70 decibels.[6]

Brains do not adapt to the repetitive and persistent sound of back-up beepers, but have evolved to process natural sounds that dissipate.[clarification needed] The sound is perceived as irritating or painful, which breaks concentration.[7][better source needed]

In some countries, back-up warning systems using blasts of white noise have become more common. White noise is more audible than monotone beeping over background noise, and one can more easily ascertain the distance and direction of the sound.[8]

Regulations in the United States[edit]

Back-up beepers or an observer are required by OSHA for earth-moving vehicles with an obstructed view to the rear and no one on the ground to help guide the driver.[9] OSHA regulation 29 CFR Part 1926.601(b)(4) requires "a reverse signal alarm audible above surrounding noise level", but only when the motor vehicle has "an obstructed view to the rear". The determination of the noise level is left to the employer.

NHTSA requires electric vehicle warning sounds to alert pedestrians in electric and hybrid vehicles manufactured after 2018, for both forward and reverse travel at low speeds.[10]


  1. ^ a b Holzman, David C. (2011-01-01). "Vehicle Motion Alarms: Necessity, Noise Pollution, or Both?". Environmental Health Perspectives. 119 (1): A30–A33. doi:10.1289/ehp.119-a30. PMC 3018517. PMID 21196143.
  2. ^ Ravo, Nick (29 May 1999). "Ed Peterson, 78, Inventor of Warning Alarm for Trucks Backing up". The New York Times.
  3. ^ "Corporate Profile". Triton Signal USA. Archived from the original on November 17, 2011. Retrieved February 11, 2012.
  4. ^ Popoff-Asotoff, Peter; Holgate, Jonathan; Macpherson, John (21–23 November 2012). "Which is Safer – Tonal or Broadband Reversing Alarms?" (PDF). Proceedings of Acoustics 2012 - Fremantle. Fremantle, Australia.
  5. ^ Bliss, James P.; Gilson, Richard D.; Deaton, John E. (27 March 2007). "Human probability matching behaviour in response to alarms of varying reliability". Ergonomics. 38 (11): 2300–2312. doi:10.1080/00140139508925269. PMID 7498189. Retrieved 5 February 2021.
  6. ^ "What Noises Cause Hearing Loss? | NCEH | CDC". 2019-10-07. Retrieved 2021-02-10.
  7. ^ Wolchover, Natalie (September 2012). "Everyday Things that Make You Dumb: Why mundane experiences can throw your mental muscles for a loop". Reader's Digest. Retrieved October 28, 2012.
  8. ^ Vaillancourt, Véronique; Nélisse, Hugues; Laroche, Chantal; Giguère, Christian; Boutin, Jérôme; Laferrière, Pascal (Dec 2013), "Comparison of sound propagation and perception of three types of backup alarms with regards to worker safety", Noise & Health, 15 (67): 420–36, doi:10.4103/1463-1741.121249, PMID 24231421
  9. ^ "OSHA Material handling equipment 1926.602(a)(9) – Audible alarms". Retrieved 9 June 2016.
  10. ^ "Quiet Car Rule: New EVs Must Emit Warning Sounds In US By 2019". Inside EVs. Retrieved 2016-11-28.