Photo credit: Chris Fithall licensed under CC BY 2.0
by Daniel Fink, MD, Chair, The Quiet Coalition
October is National Protect Your Hearing Month, and I am using the occasion to propose a revised definition of noise: noise is unwanted and/or harmful sound.
For many decades, noise has been defined as “unwanted sound,” a phrase usually attributed to the late acoustics pioneer Leo Beranek. The problem with this definition is that it implies that the perception of noise is subjective. This means that those complaining about noise have no real basis for their complaints, other than a personal reaction to noise.
The new definition acknowledges that noise can be harmful to human health and can interfere with human activity. Even if a noise is merely unpleasant, that experience is stressful. Recent research shows that stress causes vascular inflammation and cardiovascular disease.
The revised definition is supported by my article in the Fall 2019 issue of Acoustics Today, summarizing the evidence-based noise levels affecting human health and function. My article makes it clear that there can be no rational doubt that noise is harmful, and unwanted noise especially so. Sounds as quiet as 30-35 A-weighted decibels (dBA) can disrupt sleep. A good night’s sleep is important for health and function. Forty-five decibel (dB) sound can disrupt concentration and interfere with learning. At 55 dB, non-auditory health impacts of noise begin, including hypertension, cardiovascular disease, and increased mortality. These effects are best studied for transportation noise, but are seen with occupational noise exposure. At 60 dBA ambient noise, people with hearing loss have difficulty understanding speech. At 70 dBA, those with normal hearing also have difficulty understanding speech.
Seventy dB time-weighted average for 24 hours is the only evidence-based noise exposure level to prevent hearing loss, but the actual safe noise level is probably lower than that. And 85 dBA is the occupational recommended noise exposure level, not a safe noise level for the public. And as I notedin my article, the World Health Organization recommends only one hour exposure at 85 dBA daily to prevent hearing loss. Because the decibel scale is logarithmic, this is mathematically the same as 70 dB time-weighted average for a day.
Hearing loss is very common in older people, but I’ve learned that this isn’t part of normal physiological aging. Rather, presbycusis or age-related hearing loss is largely noise-induced hearing loss.
So what can you do to protect your hearing? There are two ways to protect hearing: avoid loud noise, and if you can’t, use hearing protection devices.
We only have two ears, and unlike knees they can’t be replaced. So if a noise sounds too loud, it IS too loud. And if a noise is so loud that one can’t converse without straining to speak or to be heard, the ambient noise is above 75 dBA and your hearing is at risk.
And always remember that noise is unwanted and/or harmful sound
