Editor’s note: This article is adapted with permission from Proc Mtgs Acoust. 2019; 39:050002.
The words sound and noise are used interchangeably in acoustics, electronics, and physics, but have different connotations when applied to listeners. Sound is audible acoustic energy defined as vibrations that travel through the air or another medium that can be heard when it reaches the ears of a person or an animal. Noise is usually defined as unwanted sound. In engineering, noise has the additional connotation of signals that have no meaning and vary over time, whereas sound connotes meaningful signals. A more precise definition of noise is undesired sound—a definition developed by the Acoustical Society of America for the American National Standards Institute and most commonly used in scientific and popular writings.1However, this definition needs to be expanded.
Why is a new definition of noise needed now? Definitions give words meanings in both technical and everyday usage. The world appears to be getting noisier. As long as noise is merely defined as unwanted sound, it will be difficult, if not impossible, to reverse this trend. The definition of noiseas unwanted sound implies that the perception of noise is purely subjective and that noise is merely a nuisance, thereby ignoring its harmful health impacts. It also implies a value judgment, minimizing the concerns of the person complaining about noise. Often, there is the additional implication that those who complain about noise are neurotic, weak, self-centered, or have some psychological or psychiatric problem that magnifies the impact of sounds which to others seem harmless and not bothersome.
This latter implication is incorrect. Desired sounds can cause auditory damage, and unwanted sound, even if it’s just annoying, can be stressful. Stress causes vascular inflammation, increased cardiovascular disease, and death.2 That is why I propose a new definition of noise: Noise is unwanted and/or harmful sound. Widely accepted evidence-based noise levels that affect human health and function are summarized in Table 1.
Musicians have taken umbrage at the new definition, insisting that no matter how loud their music is, it can’t be noise (personal communication). Unfortunately, the high prevalence of hearing loss and tinnitus in musicians and concertgoers demonstrates that loud music is harmful to auditory health and thus meets the new definition of noise.
A brief comparison between noise and secondhand tobacco smoke may be instructive. Both are simultaneously nuisances and health hazards, but the current definition of noise acknowledges only the nuisance aspect. For most of the 20th century, smoking was viewed as a harmless social habit, and secondhand smoke a mere nuisance. As smoking became more prevalent, those who complained about unwanted secondhand smoke were viewed as neurotic, unsocial, and selfishly concerned more about their own comfort than the harmless pleasure of smokers, even politically suspect. After the first Surgeon General’s Report on Smoking and Health in 1964 established that smoking caused lung cancer, smoking was no longer viewed as a harmless habit. A subsequent Surgeon General’s Report in 1986 documented harm from secondhand smoke exposure, including cancer in adults and respiratory disease in children. When the Environmental Protection Agency designated secondhand smoke as a Class A carcinogen in 1993, with no known safe lower level of exposure, those complaining about secondhand smoke in restaurants, airplanes, trains, buses, and workplaces were no longer just complaining about a nuisance. They were complaining about a health hazard. Smoking was quickly banned from almost all indoor spaces, and in many cities from outdoor spaces as well, leading to the largely smoke-free world we now enjoy. The new definition of noiseemphasizes the harmful effects of noise exposure. If the world can be made largely smoke-free, it can also be made quieter.
The general perception is that the world is getting noisier, but there is scarce documentation of this in the scientific literature. The only specific evidence available is for restaurants. In 1993, the average noise level in restaurants in Dayton, OH, was only 68.5 A-weighted decibels (dBA).3 (A-weighting adjusts sound measurements to reflect the frequencies of human speech. A-weighted measurements are almost always lower than unweighted measurements.) This quiet sound level now seems quaint. In 2018, the average restaurant noise levels in New York City were 77 dBA, with bars averaging 81 dBA; 31 percent of restaurants and 60 percent of bars had average noise levels above 81 dBA.4
The federal government has issued no guidelines, recommendations, or standards for non-occupational noise exposure. The only advice for the public comes from the National Institute on Deafness and Other Communication Disorders (NIDCD), which states that “long or repeated exposure to noise at or above 85 dB can cause hearing loss.” While this statement is not untrue, it is misleading. As a result, 85 decibels (dB) became the de facto federal noise exposure standard for the public. It is widely, if incorrectly, cited by audiologists as the level at which auditory damage begins. It is also used in educational programs like Dangerous Decibels and NIDCD’s Noisy Planet and as a volume limit for headphones advertised as safe for children without an exposure time. Eighty-five decibels without exposure time limit is not a safe noise level. It is derived from the NIOSH recommended occupational exposure level, which does not protect all exposed workers from hearing loss. The only evidence-based noise level to prevent hearing loss is a time-weighted average of 70 dB for 24 hours.5
Ambient noise levels in cities are high enough to cause hearing loss,6 which is not part of normal aging but largely represents noise-induced hearing loss. Noise damages cochlear synapses, most likely causing the common speech-in-noise problem where people have normal audiograms but can’t follow a conversation in high ambient noise.7 Even low-level noise exposure may have adverse effects on the brain.8 In addition, noise has well-documented but little-known non-auditory health effects, including hypertension, diabetes, obesity, psychological disorders, stress, and cardiovascular disease.9,10 The harmful effects of noise are not limited to humans. Noise also has adverse effects on animals, including birds,11fishes,12 and marine mammals.13
Awareness of noise is not enough. Educating the public about the dangers of noise is not enough. Federal health authorities need to develop guidelines, recommendations, and standards for non-occupational noiseexposure, as they have done since 1972 for occupational noise exposure. Legislation should be passed at the local, state, and national levels specifying safe noise levels and exposure times for the public, including in restaurants. Signs should be required, warning those attending rock concerts or sports events to use hearing protection. Warning labels should be required for personal listening devices, headphones, and earbuds. The new International Telegraph Union guidelines for safe listening devices/systems (H.870) should be adopted into law.
This new definition of noise can help hearing health care professionals in educating patients and the public about protecting themselves from noise. The definition of noise for humans or animals may eventually evolve to be just “Noise is harmful sound.” Until that time, perhaps as an intermediate evolutionary step, I propose this new definition: Noise is unwanted and/or harmful sound.
ACKNOWLEDGEMENTS: The author wants to acknowledge the valuable assistance and feedback of the following: David Sykes; Jan Mayes, MSc, Aud(C), RAud; Wei-Shin Lai MD; and Arthur Popper, PhD, for his help with the Acoustics Today paper on which this article is based. Any errors in this manuscript remain mine alone. I also want to thank my wife, Ruth Cousineau, MD, for her support.
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