Photo credit: Ono Kosuki
by Daniel Fink, MD, Chair, The Quiet Coalition
Earlier this month, the Mayo Clinic Health System addressed the dangers of earbud and headphone use by young people. My only quibble with the article is that it states that “any sound at or above 85 dB [decibels] is more likely to damage your hearing over time.” While that statement is true, it implies that any sound pressure level up to 84 dB is safe, without an exposure time limit. That just isn’t true. As I wrote in an article published last month in the Journal of Exposure Science and Environmental Epidemiology, the actual safe noise exposure level to prevent auditory damage may be as low as 55 A-weighted* decibels (dBA) for a single noise event and 55-60 dB time-weighted average for a day.
The 85 dB exposure level the Mayo Clinic cites is based on the National Institute for Occupational Safety and Health’s recommended exposure limit for noise. The NIOSH exposure limit doesn’t prevent hearing loss in exposed workers, isn’t safe for the public and certainly isn’t safe for young people whose auditory systems are still developing. Even for workers, the NIOSH exposure limit has to be recalculated downwards for several reasons. Lifetime noise exposure, beginning as early as age 3 and continuing for years after retirement, must be considered in these calculations.
Non-occupational noise exposure during working years must also be reconsidered. This type of noise exposure wasn’t a stated issue in 1972 when the NIOSH exposure limit was first calculated, or in 1998 when it was revised. Most Americans are exposed to noise sufficient to cause hearing loss in everyday life. More sensitive measures of auditory damage than the limited-range pure tone screening audiometry NIOSH used would undoubtedly find more prevalent auditory damage at an earlier age. And the 15 dB hearing threshold level (or a 15 dB loss in the ability to hear) is considered normal by NIOSH. But the true normal hearing threshold level is a 0 dB loss.
The only evidence-based safe noise exposure level to prevent hearing loss, a time-weighted average of 70 dB a day, was calculated by the Environmental Protection Agency in 1974. But as I wrote in the article last month, that’s probably too high. I hope increasing awareness of the dangers of noise will encourage people to protect their hearing. If something sounds loud, it’s too loud and one’s auditory health is at risk.
*A-weighting adjusts sound pressure measurements to approximate the frequencies heard in human speech.
