What is the safe noise exposure level to prevent hearing loss?

Photo credit: Mark Dalton

by Daniel Fink, MD, Chair, The Quiet Coalition

What is the safe noise exposure level to prevent noise-induced hearing loss? That’s the title of my latest article, published on April 18. I argue that this safe noise exposure level may be as low as 55 A-weighted decibels* (dBA) for a single noise exposure, and about 55-60 decibels (dB) time-weighted average for a day. That low level of noise exposure will likely protect people from getting two other auditory disorders largely caused by noise: tinnitus and hyperacusis.

The only evidence-based safe noise exposure level that I have been able to find is the Environmental Protection Agency’s calculated 70 dB safe noise exposure for 24 hours. But for the same reasons that the National Institute for Occupational Safety and Health’s recommended exposure level for workplace noise needs to be recalculated downwards, so too do the EPA’s calculations.

What are these reasons? In its calculations, NIOSH assumed workers had quiet when not at work, something that is no longer true. Noise exposure is different from most occupational exposures — like ionizing radiation or toxic solvents — because we are exposed to noise in utero and then for as long as we live. At work or at home, most people living in industrialized countries are exposed to noise levels sufficient to cause hearing loss.

Life expectancies before COVID approached or exceeded 80 years, so lifetime noise exposure must now be considered.  And, children begin using personal listening devices in early childhood. They use them nearly every day by the time they’re teens, almost invariably at too-high sound output levels. More sophisticated auditory testing than limited-frequency screening audiometry would find more prevalent auditory damage earlier than screening audiometry. The EPA calculations likely used the same studies as NIOSH relied on, defining hearing loss up to 15 dB in most studies as “normal,” when true normal hearing is with 0 dB hearing loss.

As I wrote, 55 dBA is the effective quiet level required for the human ear to recover from temporary hearing loss, and is also the sound level of normal speech in a quiet environment. To me, it appears that our ears evolved to allow us to communicate without losing hearing, but greater noise exposure damages our ears.

The article is open access and I think it’s written clearly enough to be understood by those without a scientific or medical background. I encourage all to read it, and reach out to let me know what you think. The article will appear as part of a special issue of the Journal of Exposure Science and Environmental Epidemiology guest-edited by Quiet Communities’ founder and president, Jamie Banks.

*A-weighting adjusts unweighted sound measurements to approximate the frequencies heard in human speech.

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