Do we hear too much noise in everyday life? My answer is yes, but until recently I didn’t have much scientific support for my contention. That changed when I learned about an important study by Flamme et al.
My focus is on noise exposure for public, because I think noise is a danger for everyone’s auditory health. (On the personal level, a one-time exposure to loud noise caused my tinnitus and hyperacusis, and because of those conditions loud noise bothers me.) The Centers for Disease Control and Prevention recently issued a Vital Signs communication about the dangers of noise. Loud noise has grievous consequences for our military veterans, rock musicians, even classical musicians, and, of course, workers.
What limited success I’ve had convincing others that noise is a public health hazard has come from that focus on the public, but the occupational noise literature and regulations provide a basis for my analyses. I offer two caveats: I assume that workers’ ears and the public’s ears behave the same, and I also assume that “noise is noise,” i.e., occupational and environmental noise are the same. That is, noise damages the ears whether it comes from loud machinery at work, a power tool or kitchen appliance at home, a personal music player, or a loud concert or sports event.
I usually mention workplace noise exposure only to make two points: 1) the Occupational Safety and Health Administration (OSHA) standard of 90 A-weighted decibels (A-weighting adjusts noise exposure for the frequencies of human speech, and is referred to as dBA) for 8 hours a day, 240 days a year, for 40 years at work, is too high, and 2) at least workers have that legal protection–the general public has none. There are federal standards to protect the public for food, water, motor vehicles, and airplanes, and federal recommendations or guidelines for dietary intakes of vitamins, salt, sugar, and behaviors like exercise and wearing bicycle helmets, but there is no federal standard regulating noise exposure for the public.
In 1974, the Environmental Protection Agency’s Office of Noise Abatement and Control (ONAC) calculated that the safe noise exposure level to prevent hearing loss is only 70 decibels time-weighted average for 24 hours, but it was not allowed to call the calculation a recommendation. ONAC was defunded in 1982 during the Reagan administration, and the 70 decibel safe noise level was forgotten for over 35 years until I rediscovered it.
One of the concepts in the OSHA regulations is the daily noise dose. This is the 90 dBA standard, which after an 8-hour exposure constitutes 100% of the daily noise dose. Occupational noise exposure in excess of the maximum daily dose violates the law. OSHA uses a 5 decibel (dBA) “exchange rate.” For every increase in sound level of 5 dBA, the allowable exposure time is cut in half. At 95 dBA, the permissible exposure time is only four hours. The National Institute for Occupational Safety and Health (NIOSH), on the other hand, recommends a 3 dBA exchange rate, which is the standard in most industrialized countries. This permissible exposure level is shown in tables but can be also found in online calculators. NOISH explained the difference between an occupational noise exposure standard and a safe noise level for the public on their Science Blog last year.
In 2012, Gregory Flamme and colleagues published an important paper about typical noise exposure in daily life. His method was simple: volunteers recruited in Kalamazoo, Michigan, wore highly accurate sound dosimeters for several days and the results were analyzed. (For the technically inclined, they used Etymotic ER-200 dosimeters, which are not OSHA-certified but which meet the ANSI S1.25 dosimeter standard.) A total of 8.37 person-years (73,000 person-hours) of exposure monitoring were analyzed. Flamme’s study showed that most adults in that small midwestern city got noise doses exceeding OSHA limits, even though most of them didn’t work in noisy occupations, i.e., this wasn’t workplace noise exposure. The study also showed that men got more sound exposure than women, perhaps explaining the twofold higher prevalence of hearing loss in men than in women recently reported by Hoffman. This sex difference in hearing loss prevalence has been known for decades and begins in the second decade of life.
Another important concept discussed by Flamme et al. was the idea of the auditory injury threshold (AIT). AIT is the lowest sound level at which permanent (not temporary) hearing damage begins. On the second page of his paper, Flamme provides a detailed discussion of research showing the auditory injury threshold to be only 75-78 dBA (citing studies by Mills and Nixon). After exposure to noise at or above this level, it is important to have quiet so the ears can try to recover. Due to complex mechanisms not yet fully understood, this level of quiet (the “effective quiet level”) may be as low as 48-55 dBA.
In health care, it’s hard to make money from prevention. Perhaps because of that, or perhaps because few care about hearing loss in the public, Flamme’s paper has only been cited 14 times in other scientific papers. In contrast, a paper by Arlinger in the same journal, the International Journal of Audiology, on the negative consequences of hearing loss, which can be used to justify screening for hearing loss and prescription of costly hearing aids, has been cited 326 times. I hope by this post, and by citing Flamme’s work in my own writings, this will change.
It’s clear from Flamme’s study that I was right–we do hear too much noise in everyday life. That’s why hearing loss is so common. But hearing loss shouldn’t be common and wouldn’t be if the government mandated reasonable noise limitations for the general public. And the federal government should act for one just reason: NOISE CAUSES DEAFNESS. The failure to act is all the more insidious since we know that noise-induced hearing loss is 100% preventable.
We need to press on, with news media, local elected official, boards of education, clergy who help celebrate loud wedding and other parties, sports officials, and anyone else we can think of, to try to make the world a quieter place. Let’s hope that the oft-heard phrase, “Let’s make some noise!” will soon be relegated to the dictionary category “archaic use.”