A back-up beeper also known as back-up alarm, backup beeper, or vehicle motion alarm, is a device originally intended to warn passers-by of a vehicle moving in reverse. They typically produce 1000 Hz pure tone beeps at 97-112 decibels, considerably higher than the long-term hearing loss limit of 80 decibels.
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Although originally intended as a warning device, often these alarms are used on vehicles in a situation whereby no-one is ever likely to be a passer-by. (For example, tractors in fields often use them even though no-one is ever walking behind the vehicle). The noise, however, can be heard up to 3km away and disturbs residents and people within the vicinity but who will never be within the danger zone of the vehicle itself. In places, like the City of London, this noise pollution has led to a ban on the back-up beeper and alternatives must be used instead.
Matsusaburo Yamaguchi of Yamaguchi Electric Company, Japan, invented the back-up beeper. It was first manufactured as model BA1 in 1963.
Criticism
Back-up beepers are criticized by the public and in scientific literature. Beepers top lists of complaints to government roadbuilders relating to road construction noise. There is published concern that people habituate to the ubiquitous noise, diminishing its effectiveness. Strategies such as adjusting the volume according to the ambient noise and changing the tone to include sounds above 1600 Hz and below 800 Hz for improved localization would improve the alarm, but improvements are not cost-effective for the manufacturer and, if implemented by the equipment owner, introduce liability for the owner.
Brains are not adapted for dealing with the repetitive and persistent sound of back-up beepers, but more towards natural sounds that dissipate. The sound is perceived as irritating or painful, which breaks concentration.
In some countries, such as the United Kingdom, back-up warning systems using blasts of white noise are becoming more common, and are obligatory for suppliers of some large construction projects. White noise does not have to be as loud as beeps in order to be able to be heard over background noise, and people can more easily hear from which direction the signal comes.
Ambient sensing alarms
While not addressing the criticism of the type of sound, units exist that moderate the volume based on sensing ambient sound.
Regulations in the United States of America
Back-up beepers or an observer are required by OSHA for earthmoving vehicles with an obstructed view to the rear and no one on the ground to help guide the driver. Alarms are typically loud because manufacturers do not know the ambient noise level where the machines will be used.
The relevant OSHA regulation is 29 CFR Part 1926.601(b)(4) which 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. However, because equipment is moved from place to place, the loudest alarms are often selected.