Vehicle motion alarms: necessity, noise pollution, or both?

Noise pollution chips away at the public health, interfering with our immune systems, learning, and sleep, boosting stress hormones, and contributing to cardiovascular maladies, even at levels too low to cause hearing damage.1 If annoyance level is any indication, backup beepers may be one of the most harmful noises. In a 2010 report titled Technology for a Quieter America, the National Academy of Engineering cited backup beepers as one of the six top noise sources people associated with behavioral and emotional consequences.2 And although no studies to date have assessed the public health impact of backup beepers, the unpredictability and lack of control over when the sounds are heard are characteristics that normally raise noise’s impact on public health, says Arline Bronzaft, chair of the Noise Committee of the Mayor’s Grow NYC (formerly Council on the Environment). During Boston’s Big Dig project, which rerouted much of the traffic through the heart of the city, including a major highway, people lodged more complaints about noise than about any other annoyance factor and far more complaints about backup beepers than any other noise source, says Erich Thalheimer, project’s noise control officer and the lead noise engineer at Parsons Brinckerhoff, Boston. Similarly, backup beepers topped another list, with 20 state departments of transportation identifying them as a problem in generating nighttime construction noise.3 For all their ubiquity, backup beepers are poorly designed for their job, and some of their most annoying attributes are part of that poor design, says Chantal Laroche, a professor in the Audiology/Speech Language Pathology Department at the University of Ottawa, Canada, who has devoted much of her career to investigating the practical shortcomings of alarm sounds. Their single tones, with a typical volume of 97–112 decibels (dB) at the source, are loud enough to damage hearing4 and can be heard blocks from the danger zone, says Thalheimer. Their sound is so commonplace that their warning can lose its authority through the cry-wolf phenomenon.5 For reasons having to do with the physics of sound, they also are notoriously hard to localize, further undermining their utility, says Laroche. Robert Andres, a principal with the consulting group Environmental and Safety Associates and technical advisor for the advocacy group Noise Free America, takes a slightly different view. “I don’t believe that backup beepers are necessarily poorly designed for the job. The ‘job’ is to warn people around machinery and, in most environments they do this well by providing a sound that is unique to the surroundings, loud enough to be heard under a variety of circumstances, relatively directional, and easily understood to be a warning,” he says. “Problems arise when multiple beepers are present at a site or the alarm creates an annoyance beyond the danger zone.” Technologies that could mitigate the problems with backup beepers have existed for around two decades. Nonetheless, the conventional single-tone backup alarm still dominates roads and construction sites. Now Congress has passed a bill calling for a new set of motion alarms to protect pedestrians—especially the blind—from being surprised by electric vehicles (EVs) and by those hybrid electric vehicles (HEVs) that can run entirely on electricity and that therefore can be exceptionally quiet at slow speeds.6 Will “belling” EVs and HEVs be optimally protective and minimally annoying, or will the mistakes of the past be repeated?